Low rpm Generator for efficient energy harnessing from a two stage wind turbine

BY
Abdul Rehman
Minahil Mumtaz
Muhammad Hashim
Muhammad Aftab Alam
Supervised by
Dr Arsalan Arif
Faculty of Mechanical Engineering
GIK Institute of Engineering Sciences & Technology
May 2024
Low RPM Generator for Efficient Energy
Harnessing from a Two-Stage Wind Turbine
Senior design project report

BY
Abdul Rehman 2020014
Minahil Mumtaz 2020233
Muhammad Hashim 2020302
Muhammad Aftab Alam 2020264
Supervised by
Dr Arsalan Arif
Co-Advisor
Dr Arbab Abdul Rahim
Taqi Ahmad Cheema
GIK Institute of Engineering Sciences & Technology
May 2024
Low RPM Generator for Efficient Energy
Harnessing from a Two-Stage Wind Turbine
Senior design project report

Senior Design Project Status/Completion Certificate
Group No: 14
Title: Design and Development of low rpm generator for a two-stage wind turbine.
This is to certify that the senior year design project has satisfied the following:
(i) The design part of the project is completed to a sufficient level. Specifically, the
project has achieved.
a. We have achieved the optimum design for the generator and are moving into the
fabrication stage. We are currently in the process of procuring the required material
for our generator.
b. We have also developed and finalized the circuitry for combining power from two
generators and are moving into its fabrication.
c. We are currently in the process of fabricating a gearbox for the turbine.
(ii) The students have engaged in weekly meetings and demonstrated gradual
progression of work, meeting the 6CH requirement.
(iii) The defined Scope / Objectives are.
Sr.# Objectives KPI (min. 50%)
achieved
Advisor Ext.
Examiner
a. Design Optimization
b. Turbine Integration
c. Simulation and Analysis
d. Prototype Development, Testing, and Analysis
e. Quality of Report (Technical content, breadth/depth)
(iv) Based on the above score, the project stands______________.
(complete/incomplete)
(v) I (Advisor) understand that the report may be subjected to external review.
_______________ __________________
Advisor External Examiner
(To be filled by FYP Coordinator) Good Averag
e
Poor
(vi) The overall structure of a report is in line with the provided
FME guidelines.
(vii) Students followed the given deadlines by the SDP committee
_______________ _____________
FYP Coordinator Dean FME
GIK INSTITUTE OF ENGINEERING SCIENCES & TECHNOLOGY

FYP Mapping with Complex Engineering Problem Attributes
Group No: 14
Title: Low RPM Generator for Efficient Energy Harnessing from a Two-
Stage Wind Turbine.
Problem Statement: To design, develop, and optimize a low RPM generator that can
efficiently convert low-speed mechanical input into electrical power.
CEP Attributes Mapping:
(Sr.#1 is mandatory and at least one from the remaining 2~9).
S. No Attribute Justification
1 Preamble
In-depth engineering knowledge
Our fyp used the core and in-depth knowledge of electric
machines and drives along with CAD design skills,
fabrication, and Ansys Maxwell Simulations
2 Range of conflicting requirements Design depth, size, winding factor, current and voltage
3 Depth of analysis required In details software simulations
4 Depth of knowledge required Fabrication, CAD knowledge
5 Familiarity of issues Shaft alignment, initial simulations issue with results
6 Extent of applicable codes ISO standards, IEEE 15
7 The extent of stakeholder involvement
and level of conflicting requirement
Not any
8 Consequences The generator is fabricated and working
9 Interdependence Not any
Advisor: ________________
Signature: _______________

Adherence to the Sustainable Development Goals (SDGs)
Group No: 14
Title: Low RPM Generator for Efficient Energy Harnessing from a Two-
Stage Wind Turbine
FYP Mapping with SDGs:
Table 6.1: Table showing sustainable development goals.
S. No SDG Adherence of FYP to SDG
1. Affordable and Clean Energy The proposed design provides the community
with affordable, environmentally friendly
energy solutions.
2. Partnerships Support from local organization or
government will assist in resolving energy
shortages on the highways.
3. Good Health and Well-Being This generator design can minimize energy
shortages and improve well-being by
providing clean and reliable energy.
4. Decent Work and Economic Growth Implementing this design in bulk will foster
job opportunities & offering innovative
energy solution will drive the country
economic growth.
5. Industry, Innovation, and
Infrastructure
The adoption of this unique design concept
will revolutionize the renewable energy
industry & drive the development of new
sustainable infrastructure.
6. Clean Water and Sanitation N/A
7. Zero Hunger N/A
8. Quality Education N/A
9. Gender Equality N/A
10. Reduced Inequalities N/A
11. Sustainable Cities and Communities N/A
12. Responsible Consumption and
Production
N/A
13. Climate Action N/A
14. Life Below Water N/A
15. Life on Land N/A
16. Peace, Justice, and Strong Institutions N/A
17. No poverty N/A
Advisor:______________

i
Abstract
This project report outlines the comprehensive design and development process of a low RPM
generator for a two-stage wind turbine, Wind power plant requires a generator to convert
mechanical energy into electrical energy, for this most of the generators available are kind of
high-speed induction generators which requires high rotational speed and electricity to generate
a magnetic field, while in settings like highway dividers, where moving vehicles contribute to
wind speed results in low rotational speed and having low torque effect requires a low rpm
generator. Recognizing the need for a robust solution for this application, this project
introduces a special Neodymium Type (NdFeB) Permanent Magnet Generator designed for
lower speeds ranging from 250-350 rpm, effectively addressing the low rotational torque
effects. It is specifically designed to harness energy from sources with slower rotational speeds.
In this paper, two efficient generators have been designed and several modifications are applied
to get optimum results by changing the generator design. The generator designs were created
using CAD software after which comparative EM analysis of these two generators has been
done on ANSYS Maxwell. The simulation results of the initial design with 4 poles, and 12 slots
obtained a generator speed of 350 rpm, the average induced voltage is 21.5 Volt. The simulation
of the second improved design with 6 poles, and 18 slots with the same speed resulted induced
voltage of 115 Volts. The Final design involves machine with 8 poles, 24 slots, winding factor
0.98 and depth of 4inch, can generate 362 watts of power at 250 rpm and 470 watts at 350 rpm.
The improved design gives better results and is more efficient at low speeds because the
coil(conductors) is in pair form which improves the design with its compactness and increases
the induced voltage and overall efficiency. The improved design winding is done with the help
of the standard EMETOR software which is used for electrical machines. Keeping the highway
conditions in mind, a most suitable design in the form of increased slots and coil(conductor) in
pairs, has been introduced and to verify the simulation results experimentally and to further
improve the model, a prototype has been fabricated, connected with the vertical axis wind
turbine (VAWT) and testing has been performed by replicating the real-world scenario in the
lab using a pedestal fan as a wind source. The results from the lab testing ensure the feasibility
of the application of the low rpm generator on highways.
Keywords: Wind Power, Induction generator, ANSYS Maxwell, EMETOR software,
Neodymium Magnet, electrical energy generator, VAWT.

ii
TABLE OF CONTENTS
Chapter 1....................................................................................................................................1
INTRODUCTION .....................................................................................................................1
1.1 Background .................................................................................................................1
1.2 Motivation...................................................................................................................1
1.2.1 Transforming Gradual Rotation into Electrical Energy.....................................1
1.2.2 Low Cost............................................................................................................1
1.2.3 Less Repair and Maintenance ............................................................................2
1.2.4 Harness Energy from Slow-Moving Sources ....................................................2
1.3 Problem Statement ......................................................................................................2
1.4 Scope of the Work.......................................................................................................2
1.4.1 First Phase..........................................................................................................3
1.4.2 Second Phase .....................................................................................................3
1.4.3 Third Phase ........................................................................................................3
1.5 Expected Outcomes.....................................................................................................3
1.5.1 Functional Prototype..........................................................................................3
1.5.2 Specifically designed for wind and water turbine application:..........................3
1.5.3 High Efficiency at Low Rotational Speeds........................................................3
1.5.4 Robust Construction...........................................................................................4
1.5.5 Adaptability to Varying Environmental Conditions..........................................4
1.5.6 Contribution to the Advancement of Renewable Energy Technologies............4
1.6 Report Outline.............................................................................................................4
1.7 Timeline of the Project................................................................................................5
1.8 Individual and Team Contribution..............................................................................5
Chapter 2....................................................................................................................................6
LITERATURE REVIEW ..........................................................................................................6
2.1 Literature Review........................................................................................................6
2.2 Inferences Drawn out of Literature ...........................................................................10
Chapter 3..................................................................................................................................12
DESIGN AND ANALYSIS ....................................................................................................12
3.1 Design Methodology.................................................................................................12

iii
3.2 Flow Chart.................................................................................................................12
3.3 Description of the method.........................................................................................13
3.3.1 Requirements ...................................................................................................13
3.3.2 Generator Selection..........................................................................................13
3.3.3 RPM Range......................................................................................................13
3.3.4 Generator Dimensions .....................................................................................13
3.3.5 Magnets............................................................................................................13
3.4 Rotor Design .............................................................................................................14
3.5 Stator Design.............................................................................................................14
3.6 Core Material Selection.............................................................................................15
3.7 Material Selection .....................................................................................................15
3.7.1 Magnets Dimensions........................................................................................15
3.7.2 Mechanical Integrity ........................................................................................15
3.7.3 Mounting Arrangements ..................................................................................15
3.8 Shaft Alignment ........................................................................................................16
3.9 Sealing and Protection...............................................................................................16
3.10 Process flow Diagram ...............................................................................................16
3.11 Governing equations Mathematical Modelling.........................................................17
3.11.1 Helical Savonius Turbine.................................................................................17
3.11.2 H-Darrieus Turbine..........................................................................................17
3.11.3 Faraday's Law of Electromagnetic Induction ..................................................19
3.11.4 Magnetic Flux Density (B) in a PMG..............................................................20
3.11.5 Electromagnetic Torque (T_e) in a PMG ........................................................20
3.11.6 Power Output (P_out) of a PMG .....................................................................20
3.12 Efficiency Calculation...............................................................................................21
3.13 Geometric Modeling and Design ..............................................................................21
3.13.1 Initial Design....................................................................................................21
3.13.2 Initial Design Simulation Results ....................................................................22
3.13.3 Misinterpretation of Units................................................................................22
3.14 Second Design...........................................................................................................23
3.14.1 Plot of induced voltage and flux linkage .........................................................23
3.15 Third Design..............................................................................................................29
3.15.1 Induced Voltage plot........................................................................................30

iv
3.16 Fourth Design............................................................................................................30
3.16.1 Induced voltage and flux linkage polot............................................................31
3.17 Fifth Design...............................................................................................................32
3.17.1 Induced voltage and flux linkage plot..............................................................33
3.18 Sixth Design..............................................................................................................33
3.18.1 Induced voltage and flux linkage plot..............................................................34
3.19 Final Design ..............................................................................................................35
3.19.1 Induced voltage, current and flux linkage plot ................................................36
3.20 Environmental and Social Impact .............................................................................38
3.21 Analysis codes and standards....................................................................................39
3.21.1 IEEE Standards ................................................................................................39
3.21.2 IEC Standards ..................................................................................................39
3.21.3 ISO Standards ..................................................................................................39
3.21.4 National Electrical Code (NEC) ......................................................................39
3.21.5 ASTM Standards:.............................................................................................40
3.22 Summary ...................................................................................................................40
Chapter 4..................................................................................................................................41
PHYSICAL MODEL DEVELOPMENT & TESTING ..........................................................42
4.1 Fabrication of Generator ...........................................................................................41
4.1.1 Stator Core Fabrication Process.......................................................................41
4.1.2 Punch Press or CNC Punching Machine .........................................................41
4.1.3 Shear or Cutting Machine................................................................................42
4.1.4 Stack Press or Manual Stacking.......................................................................42
4.1.5 Welding or Bonding Machine..........................................................................42
4.1.6 Rotor Core Fabrication Process .......................................................................42
4.1.7 Lathe or CNC Lathe.........................................................................................43
4.1.8 Milling Machine or CNC Milling Machine.....................................................43
4.1.9 Drill Press or CNC Drilling Machine ..............................................................43
4.1.11 Winding Process for Generator Coils ..............................................................44
4.1.12 Wire Winding Machine or Coil Winding Machine .........................................44
4.1.13 Insulation Machine or Manual Insulation........................................................44
4.1.14 Stator and Rotor Assembly..............................................................................45

v
4.1.15 Press or Manual Assembly...............................................................................45
4.1.17 Shaft and Bearing Assembly............................................................................46
4.1.18 Lathe or CNC Lathe.........................................................................................46
4.1.19 Milling Machine or CNC Milling Machine.....................................................46
4.1.20 Press or Manual Assembly...............................................................................47
4.2 Manual Assembly......................................................................................................48
4.2.1 Testing Equipment (Multimeter, Oscilloscope)...............................................48
4.2.2 Post Fabrication Work .....................................................................................49
4.3 Literature on Types of Model Development on Power Combination.......................49
4.3.1 Parallel Combination Systems.........................................................................49
4.3.2 Series Combination Systems............................................................................49
4.3.3 Hybrid Combination Systems..........................................................................50
4.3.4 Parallel-Series Combination Systems..............................................................50
4.3.5 Distributed Generation Systems ......................................................................50
4.3.6 Redundant Configuration Systems ..................................................................51
4.3.7 Dynamic Load Balancing Systems..................................................................51
4.3.8 Energy Storage Integration Systems................................................................51
4.3.9 Fuel Cell Hybrid Systems................................................................................51
4.3.10 Grid-Connected Microgrid Systems ................................................................52
4.4 Development Process ................................................................................................52
4.4.1 Addressing Counter-Rotating Turbines Issue..................................................53
4.5 Integration and Instrumentation ................................................................................54
4.6 Testing/Experimental Procedure...............................................................................55
4.7 Resistor Calculation ..................................................................................................55
4.8 Smoothing Capacitor Calculation .............................................................................56
4.9 Ripple Effect Calculation..........................................................................................57
4.10 Circuit Configuration: Voltage Regulation and Transformation ..............................58
4.11 How the Circuit Works .............................................................................................59
4.12 Summary ...................................................................................................................59
Chapter 5..................................................................................................................................60
RESULTS AND DISCUSSION..............................................................................................61
5.1 Initial Design Simulation Results..............................................................................60

vi
5.2 Updated Generator Design Simulation Results.........................................................61
5.3 Final Design Simulation Results...............................................................................61
5.4 Series Combination of Generators ............................................................................62
5.4.1 Experimental Validation ..................................................................................62
5.4.2 Analysis of Capacitance and Ripple ................................................................62
5.5 Patterns and Quality of Results.................................................................................62
5.6 Comments on Accuracy and Precision......................................................................62
5.6.1 Simulation Results ...........................................................................................62
5.6.2 Updated Generator Design...............................................................................63
5.6.3 Final Design.....................................................................................................63
5.6.4 Experimental Validation ..................................................................................63
5.6.5 Capacitance and Ripple Analysis.....................................................................63
5.7 Overall Assessment...................................................................................................63
5.8 Analysis and Discussion............................................................................................64
5.8.1 Meaning and Significance of the Results.........................................................64
5.8.2 Initial Design....................................................................................................64
5.8.3 Updated Design................................................................................................64
5.8.4 Final Design.....................................................................................................64
5.8.5 Series Combination of Generators...................................................................64
5.9 Practical Experimentation .........................................................................................64
5.9.1 Experimental Setup..........................................................................................64
5.9.2 Generator Setup ...............................................................................................65
5.9.3 Step-Down Transformer ..................................................................................65
5.9.4 Voltage Regulation ..........................................................................................65
5.9.5 Series Combination..........................................................................................65
5.9.6 Current Limiting ..............................................................................................65
5.9.7 Measurement Instruments................................................................................65
5.10 Experimental Results.................................................................................................65
5.10.1 Output Volage and Current..............................................................................65
5.10.2 Series Combination Results.............................................................................66
5.10.3 Ripple Voltage and Smoothing Capacitor .......................................................66
5.11 Detailed Calculation..................................................................................................66
5.11.1 Step- Down Transformer .................................................................................66

vii
5.11.2 Current Limiting Resistor ................................................................................66
5.11.3 Smoothing Capacitor Calculation....................................................................66
5.11.4 Ripple Effect Calculation.................................................................................67
5.12 Analysis of practical Results.....................................................................................67
5.13 Comparison with Theoretical Expectations ..............................................................67
5.13.1 Voltage Addition in Series...............................................................................67
5.13.2 Influence of RPM on Induced Voltage ............................................................68
5.13.3 Practical Transformations................................................................................68
5.14 Comparison with Results from Other Authors..........................................................68
5.14.1 Pole and Coil Configuration ............................................................................68
5.14.2 Series Combination of Generator.....................................................................68
5.15 Conclusion.................................................................................................................68
5.16 Summary ...................................................................................................................69
Chapter 6..................................................................................................................................70
IMPACT & ECONOMIC ANALYSIS ...................................................................................70
6.1 Social Impact.............................................................................................................70
6.2 Sustainability Analysis..............................................................................................71
6.3 Environmental Impact...............................................................................................71
6.4 Sustainable Development goals (SDG’s)..................................................................72
6.5 Hazard Identification and Safety Measures ..............................................................72
6.6 Summary ...................................................................................................................73
6.7 Objectives Achieved .................................................................................................73
Chapter 7..................................................................................................................................73
CONCLUSION & FUTURE RECOMMENDATION............................................................74
7.1 Conclusion.................................................................................................................74
7.2 Future Recommendations..........................................................................................75
7.3 References .................................................................................................................76

viii
NOMENCLATURE
CAD Computer-Aided Design
VAWT Vertical Axis Wind Turbine
EM Electromagnetic
CSIRO Commonwealth Scientific and Industrial Research Organization

ix
List of Figures
Figure 1-1: Gantt Chart..............................................................................................................5
Figure 2-1 Layout of the direct-drive permanent magnet..........................................................7
Figure 2-2: The “active” stator area...........................................................................................7
Figure 4 Initial 2D Design of the Generator ...........................................................................21
Figure 5 Induce voltage in Initial Design with 50 RPM..........................................................21
Figure 6 Induce voltage in Initial Design with 100 RPM........................................................22
Figure 7 Induced Voltage at 50 RPM for Different Phases....................................................23
Figure 8 Induced Voltage at 100 RPM for Final Generator Design........................................24
Figure 9 Induced Voltage at 250 RPM, Model Depth = 120 mm ..........................................25
Figure 10 Induced Voltage at 250 RPM, Model Depth = 0.5 m..............................................25
Figure 11 Induced Voltage at 300 RPM, Model Depth = 0.5 m.............................................26
Figure 12 Induced Voltage at 900 RPM, Model Depth = 0.5 m..............................................26
Figure 13 Loaded 6-Pole, 18-Slot Stator at 900 RPM, Model Depth = 0.5m .........................27
Figure 14 Torque Plot for Loaded 6-Pole, 18-Slot Depth0.5 m, 150 Conductors...................28
Figure 15 Induce Voltage Plot .................................................................................................28
Figure 16 Flux Linkage Plot ....................................................................................................29
Figure 17 Revise Model...........................................................................................................29
Figure 20 Revised Model.........................................................................................................31
Figure 23 Revised Model.........................................................................................................32
Figure 26 Revise Model...........................................................................................................34
Figure 29 Final Design.............................................................................................................36
Figure 30 Induced Current.......................................................................................................36
Figure 31 Induce Voltage.........................................................................................................37
Figure 33 Stator Core...............................................................................................................58
Figure 34 Rotor Core ...............................................................................................................58
Figure 35 Winding Process......................................................................................................35
Figure 36 Stator and Rotor Assembly......................................................................................36
Figure 37 Shaft and Bearing Assembly ...................................................................................50
Figure 38 Final Assembly and Testing....................................................................................37
Figure 39 Post Fabrication Work.............................................................................................37
Figure 40 Test Circuit..............................................................................................................58
Figure 41 Circuit Configuration...............................................................................................58

1
Chapter 1
INTRODUCTION
1.1 Background
Renewable energy sources such as wind and water turbines have gained significant attention
in recent years as viable alternatives to traditional fossil fuel-based power generation. These
turbines harness the kinetic energy of the wind or water flow and convert it into electrical
energy. One critical component of such turbines is the generator, which converts the
mechanical energy from the turbine's rotation into usable electrical power. In this project, we
aim to design and develop a low RPM generator. A low RPM generator is specifically designed
to generate electricity efficiently at slower rotational speeds. The design and development of
such generators are crucial for harnessing energy from renewable sources where the input
mechanical power is available at lower speeds. Wind turbines, for example, may not always
experience high wind speeds, and water flow in some locations might not provide rapid
rotations. In such cases, a low RPM generator becomes essential to effectively convert the
available kinetic energy into electrical power. The challenge in designing a low RPM generator
lies in optimizing its efficiency and performance at these lower speeds. It requires engineering
solutions to maximize energy conversion and adapt to variable conditions. Most generators,
such as those in power plants or portable generators, operate at higher RPMs to generate
electricity efficiently. However, low RPM generators are specifically designed for applications
where the input mechanical power is provided at slower speeds, such as wind turbines, water
turbines, or certain types of engines.
1.2 Motivation
1.2.1 Transforming Gradual Rotation into Electrical Energy
The primary function of the low RPM generator is to efficiently convert the gradual rotation
of the turbine into electrical energy. As the wind turns the turbine blades at lower speeds, the
generator's design allows it to capture and convert this kinetic energy into a usable form of
electricity. This capability is crucial for maximizing power generation in scenarios where the
rotational speeds are not high.
1.2.2 Low Cost
The emphasis on low cost suggests that the project aims to develop a cost-effective solution
for renewable energy generation. This is significant for wider adoption, especially in
applications where cost considerations play a pivotal role in decision-making. Achieving cost-

2
effectiveness involves optimizing the design, materials, and manufacturing processes without
compromising on performance and reliability.
1.2.3 Less Repair and Maintenance
A low RPM generator designed for wind turbine applications is expected to have a robust
construction, contributing to reduced repair and maintenance requirements. This characteristic
is essential for ensuring the long-term sustainability and cost-effectiveness of the renewable
energy system. Minimizing downtime due to maintenance enhances the overall efficiency and
reliability of the generator. In addition to this. The small size of the generator indicates a focus
on compact and efficient design. Compact generators are advantageous in situations where
space is limited or where portability is a key consideration. This characteristic can be especially
beneficial in various applications, including those requiring decentralized power generation or
installations with space constraints.
1.2.4 Harness Energy from Slow-Moving Sources
The versatility of the low RPM generator is underscored by its ability to harness energy from
slow-moving sources, such as rivers and streams. This expands the range of potential
deployment sites, making it suitable for locations where higher wind speeds or faster water
flows may not be consistently available.
1.3 Problem Statement
This project undertakes the comprehensive task of designing, developing, and optimizing a
low RPM generator with the specific aim of proficiently converting low-speed mechanical
input into electrical power. The core challenges lie in achieving exemplary electrical efficiency
to maximize energy conversion, ensuring scalability to cater to diverse applications and power
requirements, and maintaining cost-effectiveness for widespread adoption. Simultaneously,
the project places a paramount emphasis on upholding rigorous mechanical and electrical
safety standards. The success of this endeavor not only promises a breakthrough in renewable
energy technologies by enabling the effective utilization of energy from slower sources but
also addresses critical considerations of safety, scalability, and economic viability,
contributing significantly to the advancement of sustainable energy solutions.
1.4 Scope of the Work
This project aims to design and develop a low RPM generator that addresses the limitations of
traditional high RPM generators in wind and water turbine applications. The generator will be
optimized to operate efficiently at low rotational speeds, maximizing power generation while
minimizing mechanical stress and maintenance requirements. By achieving this, we aim to
enhance the overall performance, reliability, and cost-effectiveness of wind and water turbine
systems.

3
1.4.1 First Phase
The project will follow a systematic and iterative design and development process. The initial
phase will involve a comprehensive literature review to understand the existing technologies,
design principles, and challenges associated with low RPM generators. Based on this research,
we will identify the key parameters and performance targets for our generator.
1.4.2 Second Phase
Next, we will undertake the design phase, which includes conceptualization, modelling, and
simulation using advanced computer-aided design (CAD) tools. We will explore various
generator topologies, such as permanent magnet generators (PMGs), induction generators, and
synchronous generators, to determine the most suitable design for our low RPM application.
The design will prioritize efficient power conversion, high reliability, and compatibility with
varying wind or water speeds.
1.4.3 Third Phase
Following the design phase, we will proceed to the development and prototyping stage. This
will involve procuring the necessary materials, components, and manufacturing facilities. We
will assemble and test the generator, iteratively refining the design based on performance
evaluations and feedback.
1.5 Expected Outcomes
Upon successful completion of this project, we expect to deliver the following.
1.5.1 Functional Prototype
The primary objective of the project is to deliver a tangible and operational prototype of a low
RPM generator. This prototype will serve as a physical representation of the design and
engineering principles established throughout the project. It will demonstrate the practical
feasibility of creating a generator that operates efficiently at low rotational speeds.
1.5.2 Specifically designed for wind and water turbine application:
The focus of the low RPM generator is on catering to the unique requirements of wind turbine
systems. These renewable energy sources often operate in conditions where the available
kinetic energy may not result in high rotational speeds. The generator, therefore, is tailor-made
to work optimally in these environments, ensuring effective energy conversion.
1.5.3 High Efficiency at Low Rotational Speeds
One of the key performance metrics for the generator is its efficiency, especially when
operating at lower rotational speeds. Achieving high efficiency in this context is crucial for
extracting the maximum amount of electrical power from the slower rotations typical of wind
and water turbines. This efficiency is a measure of how effectively the generator converts the
available kinetic energy into usable electrical power.

4
1.5.4 Robust Construction
The generator is expected to be built with a robust and durable design. This is essential to
withstand the challenges posed by the environmental conditions in which wind turbines are
commonly deployed. Robust construction ensures the longevity of the generator, reducing
maintenance requirements and increasing its reliability in various operating conditions.
1.5.5 Adaptability to Varying Environmental Conditions
Renewable energy systems are often subject to changes in environmental conditions, such as
fluctuations in wind speed, water flow, and temperature. The generator is engineered to be
adaptable, meaning it can perform effectively under a range of environmental scenarios. This
adaptability enhances the reliability and versatility of the generator in real-world applications.
1.5.6 Contribution to the Advancement of Renewable Energy Technologies
The successful completion of this project is anticipated to have a broader impact on the field
of renewable energy. By improving the performance and viability of wind and water turbine
systems, the project contributes to the overall advancement of renewable energy technologies.
This advancement is crucial for promoting sustainable energy solutions and reducing reliance
on traditional fossil fuel-based power generation methods.
1.6 Report Outline
Chapter 1: Introduces the project, background, motivation for the project, problem statement,
aim and objectives, scope of the work, and project timeline.
Chapter 2: Explains the literature review and discusses the research gap found in the literature
survey.
Chapter 3: Elaborates on the design and analysis by explaining the design methodology,
process flowchart, governing equations, mathematical modeling, codes, and standards that are
utilized in the project.
Chapter 4: Explains the model development process that includes fabrication, integrating the
electronics and experimental procedure.
Chapter 5: Discusses the simulation results and details about its accuracy and comparison of
the theoretical results with other authors.
Chapter 6: Discusses the social and environmental impact of the design model and detail
about mapping of the sustainable development goals of the project.
Chapter 7: Explains the conclusion of the project, and future recommendation that could be
followed for better results.

5
1.7 Timeline of the Project
The project outline using the Gantt chart is as follows.
1.8 Individual and Team Contribution
Muhammad Hashim Contributed to extensive preliminary research for the project, the
addition of rpms of two shafts, the problem statement, Simulations and Results, fabrication
and the design analysis and testing of the turbine.
Minahil Mumtaz Contributed to extensive research in combining power from two generators
and finalizing the circuit that will be implemented for the combination of power, the
background, aims, and expected outcomes for the project and chapter 1 of this report.
Abdul Rehman Contributed to extensive research for the project, the addition of rpms of two
shafts, design, simulation and results of the design, simulation & analysis of gearbox, testing
of the turbine.
Aftab Alam Contributed to the research of combining the power from two generators, the
selection and design of the Gearbox for a combination of torques, and chapter 2 of this report.
All members of this Final Year Project contributed towards the literature review and extensive
review of case studies to finalize the design of our 8 poles, 24 slots Low RPM Generator.
Figure 1-1: Gantt Chart

6
Chapter 2
LITERATURE REVIEW
2.1 Literature Review
Wind power plants are one of the renewable energies where energy utilization is ± 3-5% from
the potential existence of wind power. Wind power plant requires a generator to convert
mechanical energy into electrical energy, mostly the generators available in the market is a
kind of high-speed induction generators that requires high rotational speed and electricity to
generate a magnetic field. While wind power plants need low-speed generators and without
initial electricity.
The problem is that most electrical generators available in the market are high-speed induction
generators, that require a high speed between 1000 rpm 1500 rpm and require the initial
electrical energy to create the magnetic field. The thermal power station, which has a generator
needs low rotation and without initial electricity, this was due to the wind speed average in
Indonesia is 3.47 m/s and in Malang 2.7 m/s (Hidayat, 2022). With wind speeds very small it
is difficult to drive a high-speed generator.
Suhardi (Irfan, Hakim, Suhardi, Kasan, Effendy, Faruq, et al., 2018) has designed and built an
electric generator at low speed with 180 rpm. However, the electrical power generator is still
very small; it is 25 watts, with an efficiency of only 25%. Budiman et al. (Irfan, Hakim,
Suhardi, Kasan, Effendy, Faruq, et al., 2018), has created and tested an axial permanent magnet
generator. The maximum electrical voltage produced at that time was 12V with a load current
of 0.14A. However, the rotation speed of the generator is still quite high i.e., 1200 rpm. With
permanent magnet material available on the market, (Lampola et al., 1998) has designed a low-
speed permanent magnet generator for wind power stations. It produced a permanent magnet
generator design with a speed of 1000 rpm and a maximum voltage generated at 38V and 114
mA electric current.
(Dilev et al., 2012) has been designed and built with the induction generator excitation system
itself. The magnets used are NdFeB permanent magnets. However, the test has not been shown
using a certain electrical load, so it was unknown how much electric power could be generated.
The use of an NdFeB permanent magnet-type generator for low speed has been successfully
done by (Irfan, Hakim, Suhardi, Kasan, Effendy, Pakaya, et al., 2018) in 2015 with a speed of
500 rpm, and 2V voltage generated.

7
A joint effort to develop a 20-kW low-speed, high-torque, direct-drive permanent magnet
generator for wind turbines was initiated by the University of Technology Sydney (UTS) and
Commonwealth Scientific and Industrial Research Organization (CSIRO) in conjunction with
the Australian Cooperative Research Centre for Renewable Energy (ACRE) and Venco-
Westwind. A non-optimized, 48-pole, 170 rpm prototype was constructed by Venco-Westwind
earlier (Chen & Nayar, 1998). It features a radial-flux, slotted-stator topology with outer-rotor
and surface-mounted Nd-Fe-B magnets, as shown in Fig. 2-1. The magnets are bonded to the
inner surface of a steel drum that rotates around a stationary stator with conventional three-
phase windings. An advantage of this arrangement is that the centrifugal force of the rotating
magnets applies pressure to the bonding media, therefore increasing the generator reliability
of the glued joint. Also, the blades of the wind turbine are directly mounted on the front surface
of the outer rotor drum, which leads to a simple assembly process (Khan et al., 2017).
Figure 2-2: The “active” stator area.
Figure 2-1 Layout of the direct-drive permanent magnet.

8
As wind turbine unit rating increases, there has been an increasing number of gearbox failures
(Osama & Lipo, 1997). Hence, there is more interest in direct-drive systems among
manufacturers, but the mass of such generators is a significant issue. Work presented at
European Wind Energy Conference (EWEC) 2007 by the authors showed that the structural
mass of a direct-drive generator can be more than 80% of the total mass (McDonald et al.,
2008).
This structural mass is required to overcome the magnetic attraction force between the
stationary and moving parts of the generator (Figure 2-3). This attraction force is a result of
the normal component of Maxwell stress. It can be 10 times the torque-producing shear stress
(Figures 2-3 and 2-4). The airgap clearance between the rotor and the stator must be
maintained; otherwise, the generator could be damaged.
The innovative step in this new concept has been to take the active materials in the machine—
copper, magnets, and steel—and change their relative positions to minimize the effects of the
normal force. The result is a machine in which the structure only must support the mass of the
active components, leading to a reduction in total mass in the region of 55% compared with
conventional permanent magnet (PM) machines. This mass reduction is due to the reduction
in structural loads.
Figure 2.3 Section of a conventional permanent magnet
generator showing (a) shear stress and (b) normal
stress.
Figure 2.4 Shear and normal stress for airgap flux densities

9
One of the paper designs and developed a 5kW, 150 rpm (Bumby et al., 2008), air-cored, axial
flux generator for use as a direct drive generator with small wind and water turbines. The
generator uses trapezoidal-shaped magnets to obtain a greater active length than that provided
by circular magnets. The armature coils are also trapezoidal. A prototype generator has been
tested and produces up to 5000W at 150 rpm with an electrical efficiency substantially greater
than 90%. The generator performs as predicted by the design process.
The development of an air-cored axial flux generator is described in (Bumby & Martin, 2005).
Key features of this generator are its simplicity of design and manufacture and the complete
absence of any cogging torque, a vital requirement for some vertical-axis wind turbines. This
generator is shown schematically in cross-section in Fig. 2-4 and uses two mild steel rotors
with permanent magnets attached to each rotor in an N-S-N-S arrangement with the N magnets
on one rotor facing the S magnets on the other. The armature is made up of several concentrated
circular coils embedded in a non-magnetic, nonconducting stator. These coils can be wound
either on a bobbin and mechanically fastened into the stator or they can be bonded into holes
in the stator using a suitable resin. The generator mounted on a 2.5 kW vertical axis wind
turbine (VAWT) undergoing performance testing is shown in Fig. 2-5 (Bumby et al., 2008).
A direct-drive generator must be light and efficient to minimize the requirements for the tower
structure and to maximize electrical power extracted from the wind (Wu et al., 2000). For small
wind turbines, direct permanent magnet generators have become very attractive because of
their high efficiency, high power density, and robust rotor structure. The attractiveness of
direct-drive permanent magnet generators is further enhanced by improvements in permanent
magnet characteristics and a decrease in material prices. Some direct examples are Enercon
12,30 kW), Proven (2.5 kw), LMW (2.5-10 kw), and Venco-Westwind (2.5-10 kw) (Ramsden,
1998).
Figure 2.5 General configuration of the Axial Flux

10
The other paper discusses the analytical design method of a 3 kW, 200 rpm radial flux
permanent magnet generator (PMG) for renewable energy power plant applications (Irasari et
al., 2013). The proposed design method is conducted in two stages, i.e. initiation and validation
stages. In the initiation stage, some of the parameters should be specified with values, such as
output power, specific magnetic loading, rotation, etc. With the new value of specific magnetic
loading, all related parameters should also be recalculated, such as the number and diameter of
the turns. Furthermore, the design is validated by testing the prototype of the generator using
water water-resistance load. The test results show that it produces 3043.64 W of power and
253.51 V of voltage at 200 rpm. Compared to the analytical calculation, the power is 0.86%
lower and the voltage is 12.45% higher. These results illustrate that the design has been
performed properly since the targeted output power can be achieved at the desired speed.
2.2 Inferences Drawn out of Literature.
When designing the generator for a particular power rating specifying the armature frequency
sets the number of poles. If circular coils are used then the diameter of the armature coils will
be related to the diameter of the magnets i.e. it will be like, but not the same. If the diameter,
number of magnets, and the pole pitch are set then the mean diameter of the generator is fixed.
The diameter of the armature coil will be like a magnet and so the length of the active area Δr
is fixed, as shown in Figure 2-2. With circular magnets it is not possible to change the number
of poles and the length of the active area independently; they are linked by the geometry of the
coils such that the active length is closely related to the pole pitch.
The consequence of this is that for a large pole number the diameter of the magnets limits the
length of the active area.
Figure 2.6 Generator mounted on a 2.5 kW VAWT.

11
This can result in a generator that has quite a large radius. For small, low-power, wind turbines
that tend to run relatively quickly this is not a significant problem as ease of manufacture is
much more important than constraining diameter (circular coils are much easier to wind than
trapezoidal ones). However, as power increases, speed reduces and the length of the active area
can be small compared to the radius, and limiting overall diameter becomes more of an issue.
Diameter can be breduced by using trapezoidal magnets when pole pitch and active length can
be decoupled for each other. Also, turbine generators have used gearboxes and pitch control
to allow constant high-speed generation under varying wind speed conditions. In recent years
contemporary power electronics of high efficiency, high reliability, and decreasing cost offer
the option to change the power frequency out of the generator to match the system frequency,
which leads to the idea of variable speed direct-drive generators. Several alternative concepts
have been proposed for direct-drive electrical generators for use in grid-connected or stand-
alone wind turbines. Compared to a conventional gearbox-coupled wind turbine generator, a
direct drive generator has reduced overall size, lower installation and maintenance cost, a
flexible control method, and quick response to wind fluctuations and load variation. For a
direct-drive wind generator, the starting torque is an important design issue because a high
starting torque prevents operation at cut-in wind speed. Consequently, it is necessary to reduce
the starting torque to acceptable values. The cogging torque (Cogging torque is the interaction
between the permanent magnets in the rotor and the slots of the stator. Because the rotor
magnets are attracted to the stator teeth, the torque required to move the rotor changes with the
relative position of the rotor to the stator) can be calculated directly for different rotor positions
when the stator winding carries no current and the remanence of the magnet is known. Since
the magnet remanence is temperature dependent, the cogging torque varies with the operating
temperature of the generator. The maximum cogging torque occurs when the rotor temperature
is at room temperature.
Figure 2-7 Rotor and Stator of an axial flux machine with
trapezoidal magnets

12
Chapter 3
DESIGN AND ANALYSIS
3.1 Design Methodology
The concept of developing a low RPM generator poses a unique set of challenges, especially
considering the abundance of existing designs tailored for high RPM applications. While
numerous generators have been engineered to function effectively at elevated rotational
speeds, none of them has been able to propose a design that would fulfill the requirements at
low rpm. The focus of this project is distinct aiming to pioneer a generator designed explicitly
for low RPM operation while maintaining high efficiency. Recognizing the existing gap in
solutions catering to this specific niche, we aim to leverage insights from prior research and
select a design that best aligns with the demands of a low RPM generator, offering a
breakthrough in efficiency for this application.
3.2 Flow Chart
The process flow chart shows the sequential steps of the design process. Starting from the
literature review and choosing the best design through ANSYS Maxwell analysis to fabricate
the final design by doing the mathematical modeling, design of gearbox, and lamination.

13
3.3 Description of the method
3.3.1 Requirements
The specific requirement for this project is to design a low RPM generator capable of
producing a minimum power output of 140 watts. The generator should operate at a voltage
compatible with DC 12V highway lights, ensuring they are adequately powered. Additionally,
the generator should be designed to operate within the commercially available frequency range
to facilitate integration with existing infrastructure.
3.3.2 Generator Selection
Given the simplicity, efficiency, and suitability for wind energy applications, Permanent
Magnet Generators (PMGs) are chosen as the preferred generator type. PMGs offer advantages
such as no starting current requirement, high efficiency, and cost-effectiveness. Their
components are readily available, facilitating easy and affordable maintenance.
3.3.3 RPM Range
The target RPM range for this generator is defined as 100 to 500 RPM, with the capability to
sustain up to 900 RPM based on experimental verification. This low RPM range is well-suited
for wind energy applications, ensuring optimal performance in moderate wind conditions
commonly encountered in outdoor environments. By focusing on low RPM operation, the
design prioritizes efficiency and power generation at lower rotational speeds, aligning with the
inherent characteristics of wind turbines.
3.3.4 Generator Dimensions
While there were no strict constraints on the size of the generator, the decision was made to
prioritize compactness and lightweight design to minimize starting torque requirements and
enhance overall efficiency. The chosen design aims to strike a balance between size, weight,
and performance, ensuring ease of integration within the wind turbine system while
maintaining optimal power output.
The selected generator design features a compact form factor, with an outer diameter of 102mm
and a shaft diameter of approximately 100mm. This compact size facilitates seamless
integration into the existing infrastructure without compromising space or airflow within the
wind turbine system. Additionally, the air gap of 1mm between the rotor and stator assemblies
optimizes magnetic flux density while minimizing losses and maximizing energy conversion
efficiency.
3.3.5 Magnets
Neodymium magnets have been selected as the preferred choice for Permanent Magnet
Generators (PMGs) due to their exceptional magnetic properties, specifically their high

14
magnetic flux density. This characteristic significantly enhances the efficiency and power
output of the generator, making it well-suited for the intended wind energy application.
These Neodymium magnets will be strategically installed in the slots of the stator assembly,
optimizing the magnetic field strength, and ensuring efficient energy conversion. By
leveraging the superior magnetic properties of Neodymium, the generator can achieve higher
power output while operating within the specified RPM range.
Additionally, for both the stator and rotor assemblies, laminated steel 1010 has been chosen to
maximize magnetic flux density. Laminated steel 1010 offers excellent magnetic properties,
including low core loss and high permeability, which are crucial for minimizing energy losses
and maximizing the efficiency of the generator. This material selection ensures optimal
performance and reliability of the generator under varying operating conditions, further
enhancing its suitability for wind energy applications.
3.4 Rotor Design
The rotor design process involved comprehensive simulations using ANSYS Maxwell
software to optimize performance and efficiency. Multiple configurations were evaluated,
considering variations in the number and shape of magnets to maximize power output and flux
linkage within the generator system.
Initially, different numbers of magnets were tested to determine their impact on generator
performance. Subsequently, various magnet shapes—including rectangular, arc, triangular,
circular, and trapezoidal—were analyzed through simulations to assess their influence on
power generation and flux linkage. Among the tested configurations, arc-shaped magnets
positioned at the outer surface of the rotor consistently yielded the most favorable results,
exhibiting superior performance in terms of power output and flux linkage. However, due to
practical constraints related to magnet availability, a compromise was made to utilize
rectangular-shaped magnets for the final design.
It was determined through extensive simulations and analysis that the optimal configuration
consisted of 6 poles of rectangular magnets. This configuration demonstrated the highest level
of efficiency and power generation capability within the specified RPM range, aligning with
the project's objectives and requirements.
3.5 Stator Design
After comprehensive simulations were performed using ANSYS Maxwell software, the
number of slots was varied from 10 slots to 36 slots, to optimize performance and efficiency.
After careful consideration of the number of slots and the effects it has on the results, the 18
slots proved to have resulted in greater power, thus the design was fabricated with 18 slots.

15
3.6 Core Material Selection
Laminated steel has been chosen as the core material for the stator assembly, aligning with
industry standards and best practices for generator design. Laminated steel offers several key
advantages that make it well-suited for this application.
Firstly, laminated steel exhibits low core loss and high magnetic permeability, which are
crucial properties for minimizing energy losses and maximizing the efficiency of the generator.
By reducing core losses, laminated steel ensures that a greater proportion of the input electrical
energy is converted into useful mechanical energy, enhancing overall efficiency. Additionally,
laminated steel is known for its excellent magnetic properties, including high saturation
induction and low hysteresis loss. These properties contribute to improved magnetic flux
density within the stator core, resulting in enhanced power generation capabilities and
increased energy conversion efficiency. Moreover, laminated steel offers mechanical strength
and durability, ensuring the structural integrity of the stator assembly under operating
conditions. The laminated construction helps mitigate eddy current losses by providing
insulation between adjacent laminations, further improving efficiency and reliability.
3.7 Material Selection
High-conductivity materials copper coils were selected for the windings to minimize resistive
losses. Additionally, laminated steel cores were chosen to reduce eddy current losses in the
stator and rotor assemblies.
3.7.1 Magnets Dimensions
The rotor and stator configurations were optimized to maximize magnetic flux density while
minimizing losses due to magnetic saturation and hysteresis. This was achieved through careful
selection of magnet shapes and placement, as well as precise calculation of air gap dimensions.
3.7.2 Mechanical Integrity
Structural components were designed to minimize mechanical losses and ensure smooth
operation. This included optimizing bearing selections, mounting arrangements, and shaft
alignments to reduce frictional losses and mechanical wear.
3.7.3 Mounting Arrangements
The generator was securely mounted within the wind turbine system to withstand
environmental stresses, vibrations, and mechanical forces. Proper mounting arrangements
were designed to distribute loads evenly and maintain structural integrity.

16
3.8 Shaft Alignment
Precision shaft alignment was crucial to minimize misalignment-induced losses and ensure
efficient power transmission between the rotor and the load. Advanced alignment techniques,
such as laser alignment, were employed to achieve optimal alignment tolerances.
3.9 Sealing and Protection
Sealing mechanisms and protective enclosures were implemented to safeguard internal
components from environmental contaminants, moisture, and corrosion, prolonging the
lifespan of the generator system and minimizing maintenance requirements. The generator
system was engineered to withstand harsh operating conditions through meticulous attention
to mechanical design considerations while maintaining optimal performance and efficiency.
By integrating high-quality components and employing best practices in mechanical
engineering, the generator system is poised to deliver reliable and consistent power generation
in wind energy applications.
3.10 Process flow Diagram.
The below process flow diagram summarizes the main steps we used to make certain decisions
to arrive at a final design diagram.

17
Figure 3 Process flow diagram
3.11 Governing equations Mathematical Modelling
3.11.1 Helical Savonius Turbine
The formula given below is to calculate the torque produced by the turbine after the
striking of wind.
T =
1
4
ρAsV2
DCT
After the calculation torque power produced by the rotor is needed to be calculated, the
formula used for the calculation of power is.
𝑃𝑟𝑜𝑡𝑜𝑟 = 𝑇 × 𝑤 (3.1)
The power produced by the rotor is different than the power transferred to the blades via
drag produced by wind, so power transferred by the air is.
𝑃
𝑚𝑎𝑥 =
1
2
𝜌𝐴𝑠𝑉3
(3.2)
The ratio of both powers gives the coefficient of power or efficiency which is.
𝐶𝑝 =
𝑃𝑟𝑜𝑡𝑜𝑟
𝑃max
(3.3)
Aspect ratio plays an important role in the efficiency of the turbine, and it is the ratio of
the height and diameter of the blade and is.
𝐴𝑠𝑝𝑒𝑐𝑡 𝑅𝑎𝑡𝑖𝑜 =
H
D
(3.4)
The speed at which air strikes the blade is the ratio of rotor velocity and wind velocity
which is.
𝑇𝑖𝑝 𝑆𝑝𝑒𝑒𝑑 𝑅𝑎𝑡𝑖𝑜 =
U
V
(3.5)
There is also a relation between the coefficient of torque and power which is.
𝐶𝑃 = 𝑇𝑆𝑅 × 𝐶𝑇 (3.6)
3.11.2 H-Darrieus Turbine
The Power available in the wind is proportional to the cube of the wind speed and the area
of the turbine A:
A = 2 R L (3.7)

18
where R and I are the radius and length of the blade, respectively.
The total power available is given as:
T =
1
2
× ρ × 𝐴 × vw
2
(3.8)
Where, 𝜌 is the density of the air and 𝑣𝑤 is the undisturbed wind speed. But as already
known is the available power limited of the Bertz criteria. It is obvious that power depends
heavily on the wind speed.
The flow velocities in the upstream and downstream sides of the Darrieus type VAWTs
are not constant. From this figure one can observe that the flow is considered to occur in
the axial direction. The chordal velocity component 𝑉𝑐 and the normal velocity component
𝑉𝑛 are, respectively, obtained from the following expressions:
𝑉𝑐 = 𝑅𝜔 + 𝑉𝑎𝑐𝑜𝑠𝜃 (3.9)
𝑉𝑛 = 𝑉𝑎 𝑠𝑖𝑛𝜃 (3.10)
where Va is the axial flow velocity (i.e., induced velocity) through the rotor, ω is the
rotational velocity, R is the radius of the turbine, and θ is the azimuth angle. The angle of
attack (alpha) can be expressed as,
α = 𝑡𝑎𝑛−1
(
𝑉𝑛
𝑉𝑐
) (3.11)
Figure 3-1 Free Body Diagram of Aero foil

19
The directions of the lift and drag forces and their normal and tangential components. The
tangential force coefficient (𝐶𝑡)is basically the difference between the tangential components
of lift and drag forces. Similarly, the normal force coefficient (𝐶𝑛) is the difference between
the normal components of lift and drag forces. The expressions of 𝐶𝑡 and 𝐶𝑛 can be written as
𝐶𝑡 = 𝐶𝑙𝑠𝑖𝑛𝛼– 𝐶𝑑𝑠𝑖𝑛𝛼 (3.12)
𝐶𝑛 = 𝐶𝑙𝑠𝑖𝑛𝛼 + 𝐶𝑑𝑠𝑖𝑛𝛼 (3.13)
The net tangential and normal forces can be defined as
𝐹𝑡 = 𝐶𝑡
1
2
ρ ⋅ 𝑓 ⋅ 𝑙 ⋅ 𝑉2
𝐹
𝑛 = 𝐶𝑛
1
2
𝜌 ⋅ 𝑓 ⋅ 𝑙 ⋅ 𝑉2
Where 𝜌 is the air density, 𝑓 is the blade chord, 𝐼 is the length of the blades and 𝑉 is the relative
flow velocity, which is the velocity of wind. Since the tangential and normal forces are for any
azimuthal position, they are considered as a function of azimuth angle 𝜃. Average tangential
force (Fta) on one blade can be expressed as, and the total torque for the number of blades (N)
is obtained as,
𝑇 = 𝑁𝐹𝑡𝑎𝑅
And for the power,
𝑃 = 𝑇 ⋅ ω
The governing equations for Permanent Magnet Generators (PMGs) describe the relationship
between the electrical, magnetic, and mechanical variables within the generator system. Here
are the fundamental equations used for modeling PMGs:
3.11.3 Faraday's Law of Electromagnetic Induction
Faraday's law describes the generation of electromotive force (EMF) in a conductor when
subjected to a changing magnetic field. This law forms the basis for understanding how PMGs
produce electrical power.
Mathematically, Faraday's law can be expressed as
𝐸 = −𝑁
𝑑Φ
𝑑𝑡
E is the induced voltage (EMF) in volts (V).
Φ is the magnetic flux in Weber (Wb).
t is time in seconds (s).

20
N is the number of turns or loops
3.11.4 Magnetic Flux Density (B) in a PMG
The magnetic flux density within the air gap of the PMG is a critical parameter that determines
the induced voltage and power output.
The magnetic flux density (B) is related to the magnetic field strength (H) by the magnetic
permeability (μ) of the material.
Mathematically, this relationship can be expressed as:
B = μ ⋅ H𝐵 = 𝜇 ⋅ 𝐻
B is the magnetic flux density in Tesla (T).
𝜇 is the magnetic permeability in Henrys per meter (H/m).
𝐻 is the magnetic field strength in Ampere-turns per meter (A/m).
3.11.5 Electromagnetic Torque (T_e) in a PMG
The electromagnetic torque produced by the interaction between the magnetic field and the
current-carrying conductors in the PMG is responsible for mechanical power generation.
Mathematically, the electromagnetic torque can be expressed as:
Tem = K ⋅ B ⋅ I ⋅ r𝑇𝑒𝑚 = 𝐾 ⋅ 𝐵 ⋅ 𝐼 ⋅ 𝑟
Tem is the electromagnetic torque in Newton-meters (Nm).
𝐾 is a constant determined by the geometric and magnetic properties of the generator.
𝐵 is the magnetic flux density in Tesla (T).
𝐼 is the current flowing through the conductors in Amperes (A).
𝑟 is the radius of the rotor in meters (m).
3.11.6 Power Output (Pout) of a PMG
The power output of the PMG is the product of the induced voltage and the current flowing
through the load.
Mathematically, the power output can be expressed as
Pout = E ⋅ I𝑃𝑜𝑢𝑡 = 𝐸 ⋅ 𝐼
Powers are in Watts (W).
E is the induced voltage (EMF) in Volts (V).
I is the current flowing through the load in Amperes (A).

21
3.12 Efficiency Calculation
Efficiency in ANSYS Maxwell simulations is typically computed as the ratio of output power
to input power, accounting for losses in the system. The efficiency equation can be expressed
as:
Efficiency =
Pout
Pin
These equations form the foundation for solving electromagnetic problems in ANSYS
Maxwell software and computing various quantities such as current, voltage, power,
efficiency, flux density, and magnetic field distributions in electromagnetic systems. These
equations provide the foundation for modeling the electrical, magnetic, and mechanical
behavior of Permanent Magnet Generators, enabling the analysis and optimization of their
performance for various applications.
3.13 Geometric Modeling and Design
3.13.1 Initial Design
Following figure 4 illustrates the initial 2D design of the generator, featuring 4 poles and a
single set of coils in its stator. The original design served as the starting point for our
investigation into the generator's performance. However, during the initial simulations, it
became evident that the induced voltage in its 3-phase windings was relatively low.
Figure 4 Initial 2D Design of the Generator
Figure 5 Induce voltage in Initial Design with 50 RPM

22
3.13.2 Initial Design Simulation Results
This figure presents the simulation results for the initial 2D design of the generator at a low
rotational speed of 50 RPM. In Phase A, the induced voltage was measured at 2.2769 V, while
Phase B exhibited 1.8668 V, and Phase C recorded 2.2759 V.
3.13.3 Misinterpretation of Units
Upon further investigation, it was realized that there was a misunderstanding of units in the
initial simulations. The reported depth of 1 meter was incorrect, and appropriate adjustments
have been made to rectify this misunderstanding, in the succeeding report.
Moreover, it's important to highlight that the recorded values are based on a low RPM scenario
(50 RPM), which is notably lower than the rotational speeds typical in conventional high RPM
generators.
This figure depicts the simulation results for the updated generator design as RPM increased
from 50 to 100. Noticeable improvements in induced voltage across all phases (Phase A:
3.9169 V, Phase B: 4.2879 V, Phase C: 0.8863 V) signify enhanced power generation
efficiency. The increase in RPM positively influences induced voltage, showcasing the
effectiveness of design modifications. However, concurrent fluctuations in voltage reveal a
rise in cogging torque. Addressing these variations is essential to optimize generator
performance.
Further sections explore the trade-offs between induced voltage gains and cogging torque
challenges, proposing strategies for an efficient low RPM generator design.
Figure 6 Induce voltage in Initial Design with 100 RPM

23
3.14 Second Design
In the figure below, the design has been further improved by changing not only the location of
the magnets but the set of single layers of winding has been changed into a double layer of
winding. Also, the machine has been changed from 4 poles to 6 poles showing improvements
in the voltage and current as shown in the simulation results.
Figure 3-2 Final 2D Design of the Generator with Enhancements
3.14.1 Plot of induced voltage and flux linkage
Following is shown the plot of induced voltage and flux linkage over time.
Figure 3.3 Induced Voltage at 50 RPM for Different Phases
Magnets
Double set of coils in
Armature Windings
Rotor
Stator

24
This figure illustrates the induced voltage results for the generator operating at 50 RPM with a
depth of 120 mm and 100 conductors per turn. In Phase A, the induced voltage is recorded at
0.2567 V, Phase B exhibits 0.7282 V, and Phase C shows -0.9959 V. These results provide
insights into the induced voltage characteristics at the specified RPM and design parameters,
serving as a foundation for the assessment of generator performance. Subsequent figures and
sections will explore variations in induced voltage as RPM increases and further design
optimizations are implemented.
Figure 3.4 Induced Voltage at 100 RPM for Final Generator Design
This figure provides the simulation results for induced voltage in each phase (Phase A: 1.9488
V, Phase B: 4.8198 V, Phase C: -6.8432 V) at 100 RPM for the final 2D generator design. The
increased rotational speed demonstrates a continued positive impact on induced voltage,
showcasing the effectiveness of design enhancements.

25
Figure 7 Induced Voltage at 250 RPM, Model Depth = 120 mm
This figure presents the induced voltage results for the generator operating at 250 RPM with a
model depth of 120 mm. The simulation indicates an induced voltage of 0.4677 V in Phase A,
1.1567 V in Phase B, and -1.6424 V in Phase C.
Figure 3.5 Induced Voltage at 250 RPM, Model Depth = 0.5 m
This figure displays the induced voltage results for the generator operating at 250 RPM with a
model depth of 0.5 meters. The simulation reveals an induced voltage of 0.4677 V in Phase A,
1.1567 V in Phase B, and -1.6424 V in Phase C.

26
This figure depicts the induced voltage results for the generator operating at 300 RPM with a
model depth of 0.5 meters. The simulation indicates an induced voltage of 0.0004 V in Phase
A, 0.0011 V in Phase B, and -0.0015 V in Phase C.

27
This figure illustrates the induced voltage results for the generator operating at 900 RPM with
a model depth of 0.5 meters. The simulation reveals an induced voltage of 0.005 V in Phase
A, 0.0015 V in Phase B, and -0.0021 V in Phase C
Figure3.8 Loaded 6-Pole, 18-Slot Stator at 900 RPM, Model Depth = 0.5 m, 150 Conductors
This figure presents simulation results for the loaded 6-pole, 18-slot big stator operating at 900
RPM. With a model depth of 0.5 meters and 150 conductors, the induced voltage is observed
at 0.7369 V in Phase A, 1.6534 V in Phase B, and -2.4244 V in Phase C under load conditions.
These results provide a detailed view of the generator's performance with a loaded
configuration and specific design parameters. Further analysis will explore the impact of the
loaded condition on induced voltage, offering insights into the stator's efficiency and overall
suitability for practical applications.

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Figure 3.9 Torque Plot for Loaded 6-Pole, 18-Slot Stator at 900 RPM, Model Depth = 0.5 m, 150
Conductors
This figure illustrates the torque plot for the loaded 6-pole, 18-slot big stator operating at 900
RPM. With a model depth of 0.5 meters and 150 conductors, the torque characteristics under
load conditions are depicted, providing valuable insights into the stator's performance.
Figure 3.10 Induce Voltage Plot

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Figure 3.11 Flux Linkage Plot
3.15 Third Design
The model has been further modified by redefining the shape of the magnets. The magnets
have been moved toward the stator, also its dimension has been changed. The magnetic flux
plot shows the distribution of the field lines across the generator.
Figure 3.12 Revise Model

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3.15.1 Induced Voltage plot
Following is shown the plot of three phase induced voltage over time.
3.16 Fourth Design
From the figure, it can be noted that the shape of the magnets has been changed from a
rectangular to a vertical shape of the magnets to check the feasibility and results of this
vertical shape too.

31
Figure 3.15 Revised Model
3.16.1 Induced voltage and flux linkage plot

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3.17 Fifth Design
From the figure below, it can be noted that the shape of the magnets has been changed to two
split rectangular magnets. The reason behind using these magnets is that these magnets can be
easily manufactured and easily installed in the generator. Because it covers more surface area
with its unique shape, it provides better flux linkage compared to other magnets of the same
volume.
Figure 3.17 Revised Model

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3.18 Sixth Design
In this revision, the arc shape magnets were tried for better results. The area distribution of
these magnets was near the stator, and it provides better flux linkage compared to other
magnets of the same volume.so its results were better out of all shapes of magnets.

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Figure 3.20 Revise Model

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3.19 Final Design
After performing numerous simulations on ANSYS Maxwell and experimenting with various
shapes of magnets, along with altering the number of poles and slots, we reached a pivotal
decision. Through this exhaustive process, we discovered that a design featuring 8 poles and
24 slots was the optimal configuration. This conclusion was drawn from extensive analysis,
which revealed that this specific design offered superior performance metrics. The flux
linkage, voltage, and current characteristics of the 8 poles and 24 slots configuration
consistently outperformed all other designs tested. The empirical data gathered from these
simulations provided clear evidence that this configuration was the most efficient and effective
for our low RPM generator.
The comprehensive testing and simulation phase was critical in refining our generator design.
By meticulously adjusting the magnetic components and re-evaluating the electromagnetic
properties, we ensured that every iteration was thoroughly assessed. The resulting design not
only demonstrated enhanced flux linkage but also exhibited significantly improved voltage and
current output. This meticulous approach allowed us to achieve a design that not only met but
exceeded our initial performance expectations. Consequently, the decision to proceed with the
8 poles and 24 slots configuration was supported by robust experimental results, ensuring that
our generator would operate with maximum efficiency and reliability in real-world
applications.

36
Figure 3.23 Final Design
3.19.1 Induced voltage, current and flux linkage plot
Following is shown the plot of induced voltage and flux linkage over time with the winding
factor of 0.8.
Figure 3.24 Induced Current

37
Figure 3.25 Induce Voltage
This figure represents the final 2D design of the generator, showcasing notable improvements
made to address the initially low induced voltage. In contrast to the initial design (Figure 4),
the final design features a substantial modification: an increase in the number of poles from 4
to 8. Additionally, the armature windings have been updated to incorporate two sets of coils, a
departure from the single set of coils in the original design. These enhancements were
implemented to optimize the generator's performance and increase the induced voltage in its
3-phase windings.

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Design No RPM Poles Slots Power
1st
250 4 12 0.05 watts
2nd
250 6 18 72 watts
3rd
250 6 18 145 watts
Final 250 8 24 362 watts
The 2D model of the generator, characterized by 24 slots, 8 poles, and a length of 4 inches,
showcases a carefully thought-out design process. In this configuration, the stator design
incorporates 24 slots, each with its winding, while the poles dictate the magnetic configuration.
The rotor, with a deliberate salient pole design, seamlessly complements the stator, optimizing
energy conversion efficiency. This 2D design includes a strategic arrangement of coils
(conductors) in pairs within the stator slots. This pairing not only enhances the compactness of
the generator but also serves to increase the induced voltage, consequently increasing overall
efficiency. The winding configuration within the 24 slots is thoughtfully arranged to ensure a
balanced distribution, with meticulous consideration given to factors such as wire gauge and
insulation. Thus, this generator was able to generate about 175 watts, 362 watts, and 458 watts
of power for 150 RPM, 250 RPM, and 350 RPM respectively, with a power factor of 0.92 and
winding factor of 0.98.
3.20 Environmental and Social Impact
There are significant environmental benefits associated with the development and
implementation of low RPM generators. Due to the need for more substantial infrastructure
and resources, traditional high-speed generators frequently result in higher energy
consumption along with associated environmental effects. On the other hand, the low RPM
generator is intended to maximize power production at lowered rotational speeds. There are
important two advantages to the environment through this. First, it reduces the need for larger
rotating speeds, which lessens the requirement for complex and resource-intensive setups.
Second, by effectively utilizing energy at slower speeds, the generator contributes to greener
and more sustainable energy practices, which is in line with international initiatives to mitigate
climate change and cut carbon emissions. The initiative's dedication to reducing its negative
environmental effects is demonstrated by this move toward a greener energy conversion
method.
Energy obtained from clean and green sources has a huge impact on society, by providing
small riverfront settlements or low-speed speed reliable, and consistent power sources, the
generator's installation in such regions has the potential to significantly improve the social
environment. Addressing the energy demands not only enhances the quality of life for the
inhabitants but also encourages economic growth and enhancement of the community. The
well-being of communities is often affected by the intrusive vibrations and noise produced by

39
conventional high-speed generators. The compact design also helps and addresses this issue
by operating more discreetly at lower speeds and promoting an atmosphere where the
production of energy merges in with the peace of the surroundings. In essence, in different
energy-deprived environments, the low RPM generator appears not only as a technological
innovation but also as a catalyst for beneficial environmental and social change.
3.21 Analysis codes and standards
In the design and development of low RPM Permanent Magnet Generators (PMGs), several
codes and standards are commonly referenced to ensure safety, performance, and compliance
with industry best practices. Here are some of the key codes and standards used:
3.21.1 IEEE Standards
• IEEE 115: IEEE Standard Test Procedures for Synchronous Machines: This standard
provides guidelines for testing synchronous machines, including PMGs, to determine
their electrical and mechanical characteristics.
• IEEE 1580: IEEE Standard for Qualifying Class 1E Electric Cables, Field Splices, and
Connections for Nuclear Power Generating Stations: Relevant for PMGs used in
nuclear power applications, this standard specifies requirements for electric cables and
connections.
3.21.2 IEC Standards
• IEC 60034: Rotating electrical machines: This series of standards covers various
aspects of rotating electrical machines, including PMGs. Standards such as IEC 60034-
2-1 (Part 2-1: Standard methods for determining losses and efficiency from tests) and
IEC 60034-30-1 (Part 30-1: Efficiency classes of line operated AC motors (IE code))
may be applicable.
• IEC 60068: Environmental testing: This series of standards specifies environmental
testing procedures to assess the resistance of equipment, including PMGs, to various
environmental conditions such as temperature, humidity, and vibration.
3.21.3 ISO Standards
• ISO 8528: Reciprocating internal combustion engine driven alternating current
generating sets: This standard specifies requirements and test methods for AC generator
sets driven by reciprocating internal combustion engines, which may include PMGs.
• ISO 8528-1: Reciprocating internal combustion engine driven alternating current
generating sets - Part 1: Application, ratings, and performance: This part of ISO 8528
provides guidelines for the application, ratings, and performance of AC generator sets,
including PMGs.
3.21.4 National Electrical Code (NEC)
• The NEC, published by the National Fire Protection Association (NFPA), provides
requirements for electrical installations in the United States. Relevant sections for

40
PMGs may include Article 445 (Generators) and Article 705 (Interconnected Electric
Power Production Sources).
3.21.5 ASTM Standards:
• ASTM F1554: Standard Specification for Anchor Bolts, Steel, 36, 55, and 105-ksi
Yield Strength: This standard specifies requirements for steel anchor bolts commonly
used to secure PMGs to their mounting structures.
These codes and standards provide a framework for the design, development, testing, and
installation of low RPM Permanent Magnet Generators, ensuring they meet safety,
performance, and regulatory requirements. Compliance with these standards helps to mitigate
risks, ensure reliability, and facilitate interoperability in various applications and industries.
The proposed design of a low RPM Permanent Magnet Generator (PMG) for wind energy
generation carries both environmental and social impacts, which should be carefully
considered.
3.22 Summary
The design and development of a low RPM Permanent Magnet Generator (PMG) involves a
systematic approach to ensure efficiency, reliability, and compliance with industry standards.
Initially, the specific requirements of the generator, such as power output and voltage, are
defined to guide the design process. Permanent Magnet Generators (PMGs) are typically
chosen for their simplicity, efficiency, and reliability, making them well-suited for renewable
energy applications. Once the generator type is selected, attention turns to determining the
optimal RPM range for efficient operation, typically below 500 RPM for low RPM
applications like wind turbines. Considerations for the physical size of the generator prioritize
compactness and lightweight design to minimize starting torque requirements while
maximizing power output. The choice of magnetic materials, such as Neodymium magnets
and laminated steel, plays a crucial role in optimizing magnetic flux density and efficiency
within the rotor and stator assemblies. Advanced simulation tools are utilized to fine-tune the
design of these components, optimizing configurations, magnet shapes, winding layouts, and
core materials for maximum performance. Efficiency optimization strategies focus on
minimizing losses due to resistance, hysteresis, and eddy currents, ensuring that a greater
proportion of the input electrical energy is converted into useful mechanical energy. Robust
mechanical design considerations, including high-quality bearings, mountings, and shaft
alignments, minimize frictional losses and mechanical wear, ensuring smooth operation and
longevity. Throughout the design and development process, adherence to industry standards
such as IEEE, IEC, ISO, and NEC are paramount to ensure compliance, safety, and reliability.

41
Chapter 4
PHYSICAL MODEL DEVELOPMENT & TESTING
4.1 Fabrication of Generator
4.1.1 Stator Core Fabrication Process
Figure 4. stator core
4.1.2 Punch Press or CNC Punching Machine
A punch press or a CNC (Computer Numerical Control) punching machine is used to punch
out the stator laminations from sheet metal. This process involves using a punch and die set to
cut out the precise shapes required for the stator laminations. CNC punching machines are
particularly advantageous due to their precision and ability to handle complex designs and high
production volumes efficiently. They ensure that the laminations are consistent and accurate,
which is critical for the performance of the stator core.

42
4.1.3 Shear or Cutting Machine
After the laminations are punched out, a shear or cutting machine is used to trim the
laminations to their final size. This step is essential for ensuring that the laminations fit
perfectly into the stator assembly. The cutting machine provides clean, precise edges which
help in reducing eddy current losses and enhancing the overall efficiency of the motor. Proper
sizing of laminations is crucial to maintain the mechanical and electrical integrity of the stator
core.
4.1.4 Stack Press or Manual Stacking
Once the laminations are cut to size, they need to be stacked together to form the stator core.
This can be done using a stack press or through manual stacking. A stack press automates the
stacking process, ensuring that the laminations are aligned accurately and compressed
uniformly. Manual stacking, although labor-intensive, can be used for smaller production runs
or specialized applications. Proper stacking is vital to minimize air gaps and ensure the
magnetic properties of the core are optimized.
4.1.5 Welding or Bonding Machine
The final step in stator core fabrication is to bond the stacked laminations together. This can
be done using a welding or bonding machine. Welding typically involves spot welding or laser
welding the laminations at specific points to hold them together. Alternatively, bonding can be
achieved using adhesives or interlocking mechanisms. This step ensures the structural integrity
of the stator core, maintaining its shape and alignment during operation. Proper bonding
reduces vibrations and noise, contributing to the overall durability and performance of the
motor. By following these steps meticulously, the stator core can be fabricated to high
standards, ensuring reliable and efficient motor performance.
4.1.6 Rotor Core Fabrication Process
Figure 4.2 rotor core

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4.1.7 Lathe or CNC Lathe
A lathe or CNC (Computer Numerical Control) lathe is employed for turning the rotor shaft
and core to achieve the desired dimensions and surface finish. This process involves rotating
the rotor blank while a cutting tool shapes it to the specified diameter and length. CNC lathes
provide high precision and repeatability, ensuring that the rotor shaft and core are perfectly
concentric and balanced. Accurate turning is crucial for the rotor's performance, minimizing
vibrations and ensuring smooth rotation within the motor.
4.1.8 Milling Machine or CNC Milling Machine
After the rotor shaft and core are turned, a milling machine or CNC milling machine is used to
machine additional features on the rotor core, such as keyways, slots, or other profiles. Milling
involves removing material using rotating cutting tools to create these precise shapes and
features. CNC milling machines offer the advantage of automation and high accuracy, enabling
complex geometries to be machined with tight tolerances.
This step is essential to ensure that the rotor core interfaces correctly with other motor
components and performs optimally.
4.1.9 Drill Press or CNC Drilling Machine
For rotors that incorporate permanent magnets, a drill press or CNC drilling machine is used
to drill holes for the magnets. This process involves accurately positioning and drilling holes
in the rotor core where the magnets will be inserted. CNC drilling machines provide precise
control over the hole size, depth, and location, which is critical for maintaining the rotor's
balance and ensuring the magnets are securely positioned. Proper drilling ensures that the
magnetic field is correctly aligned, which is vital for the motor's efficiency and performance.
4.1.10 Welding or Bonding Machine
The final step in rotor core fabrication involves bonding the magnets to the rotor core. This
can be achieved using a welding or bonding machine. Welding, such as spot welding or laser
welding, securely attaches the magnets to the core, ensuring they remain in place during
operation. Alternatively, adhesives or bonding agents can be used to attach the magnets,
providing a strong and durable bond. Proper bonding is crucial to prevent the magnets from
shifting or coming loose, which could compromise the motor's functionality and lifespan.
By following these detailed fabrication steps, the rotor core can be manufactured to meet
stringent performance and reliability standards, ensuring the motor operates efficiently and
effectively.

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4.1.11 Winding Process for Generator Coils
Figure 4.5 Generator coils
4.1.12 Wire Winding Machine or Coil Winding Machine
A wire winding machine or coil winding machine is used for winding the copper wire to create
the generator coils. This machine automates the process of wrapping wire around a core or
bobbin in precise, evenly spaced layers. Coil winding machines can be programmed to control
the number of turns, the tension of the wire, and the pattern of the winding. This precision is
crucial for ensuring that the coils have the correct inductance, resistance, and capacitance.
Proper winding enhances the electrical performance and efficiency of the motor, reduces the
risk of short circuits, and ensures consistent coil quality.
4.1.13 Insulation Machine or Manual Insulation
After the coils are wound, they need to be insulated to prevent electrical shorts and ensure safe
operation. This can be done using an insulation machine or through manual insulation
techniques. An insulation machine applies insulating materials, such as varnish, enamel, or
insulating tape, uniformly and efficiently. Manual insulation involves manually wrapping or
coating the coils with insulating materials. Proper insulation is critical to protect the copper
wire from environmental factors, electrical stresses, and mechanical wear. Effective insulation
enhances the durability and reliability of the motor, ensuring long-term performance and
safety.

Low rpm Generator for efficient energy harnessing from a two stage wind turbine

Low rpm Generator for efficient energy harnessing from a two stage wind turbine

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