This document discusses DC generators and motors. It describes that a DC generator converts mechanical energy to electrical energy, while a DC motor converts electrical energy to mechanical energy. It then discusses the working principles of DC machines based on Faraday's laws of electromagnetic induction. The document proceeds to describe the construction of a DC machine, including its stator, rotor, field windings, armature, commutator, and brushes. It also provides equations for calculating the induced EMF in a DC generator.
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Notes made in my Final Year of Bachelor in Dental Surgery from Subject Oral & Maxillofacial Surgery. In this i have mentioned the 8 principles which are used in the treatment & prevention of odontogenic infection which are most common in dental practice. This documents is for professional dental undergraduates studying in their 4th year of BDS or DDS.
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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
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Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
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This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
1. RG,RSET
When a machine converts mechanical energy into electrical energy which
is DC in nature, it is called as a DC Generator.
ME EE
Whenever a machine converts electrical energy which is DC in nature, into
mechanical energy, it is called a DC Motor.
EE ME
DC Machines
2. RG,RSET
Working Principle
Faraday’s Laws of Electro magnetic Induction.
Whenever a conductor cuts the flux of a magnetic field, an emf is
produced in the conductor. If the two ends of the conductor are connected
to an outside circuit, the induced emf causes current to flow in the circuit.
The direction of induced current is given by Fleming’s right hand rule.
DC Generator
3. RG,RSET
Consider a single turn coil rotating about its own axis in a magnetic field.
The two ends of the coil are connected to split rings(commutator)
Single Turn Generator
4. RG,RSET
EMF induced in coil is proportional to rate of change of flux.
When the plane of coil is at right angles to the direction of field, flux linked with coil is maximum, but rate of change
of flux is minimum. Hence induced EMF is minimum.
When the plane of coil is at parallel to the direction of field, flux linked with coil is minimum, but rate of change of
flux is maximum. Hence induced EMF is maximum.
Inoredr to get a unidirectional current in external circuit, a split ring arrangement is done.
Single Turn Generator
5. RG,RSET
By winding more coils on the rotor, and bringing the ends of each coil out to separate pair of
segments on the commutator that are opposite each other, the pulsations or ripple in the output
e.m.f. is reduced
Two Coil Generator
6. RG,RSET
Construction
Same for DC Generator and Motor
A DC machine essentially consists of two parts.
1. Stator(Stationary Part) – Magnetic Field System
2. Rotor(Rotating Part) – A system of conductors
DC Generator
7. RG,RSET
Stator Rotor
1. Yoke 1. Shaft
2. Pole Core 2. Armature Core
3. Pole Shoes 3. Armature Windings
4. Field Coils 4. Commutator
5. Interpoles 5. Brushes
DC Machine - Construction
8. RG,RSET
Yoke
Hollow cylinder made of cast steel or roll steel
Act as outer protective cover of machine.
Provides mechanical support for poles.
Carries flux produced by poles
DC Machine - Construction
9. RG,RSET
Pole Core and Pole Shoes
Field windings are wound on pole core and supported by pole shoes.
Are made of number of sheet steels stacked and riveted together.
made of Silicon steel – to reduce hysteresis loss
laminated – to minimize eddy currents
Pole cores are then bolted to yoke.
Pole shoes serve two functions
1. support field coils
2. spread out flux in airgap
DC Machine - Construction
10. RG,RSET
Field Windings
are made of copper wire
Field coils are former wound to correct dimension and then put into place
over the core.
When energized with DC,
electro magnetize the poles
and provide the working flux.
All coils are connected in series
such that as current flows,
alternate N and S poles are produced.
DC Machine - Construction
11. RG,RSET
Inter Poles
Fitted to yoke between main poles.
Windings are made of copper and are connected in series with field
windings.
Flux produced by inter poles provides spark less commutation.
DC Machine - Construction
12. RG,RSET
Shaft
Provides mechanical strength to armature and commutator.
Rotor assembly is free to rotate by two bearing fixed between shaft and
two end covers.
Transfers mechanical energy to and from machine.
DC Machine - Construction
13. RG,RSET
Armature Core and Windings
Laminated cylinder mount on shaft.
Are made of number of sheet steels stacked and riveted together.
made of Silicon steel – to reduce hysteresis loss
laminated – to minimize eddy currents
Has slots on outer periphery to
accommodate armature windings.
DC Machine - Construction
14. RG,RSET
Commutator
Ends of armature coils terminated at commutator segments
Made of copper segments insulated by mica
Functions
Collect current from armature conductors.
The e.m.f. generated in the
armature conductors is alternating
e.m.f. The commutator helps in
converting this alternating e.m.f.
into a direct one.
DC Machine - Construction
15. RG,RSET
Brushes
Made of graphite or carbon
Held by brush holders
Desirable Properties
Good electrical conductivity
Less co-efficient of friction.
Functions
The brushes collect the armature current from the commutator segments
and supply it to the load (in the case of generator) or feed the current into
the commutator segments (in the case of motor).
DC Machine - Construction
16. RG,RSET
Wave Winding
Armature winding is divided into two parallel paths.
Lap Winding
Armature winding is divided into as many parallel paths as number of poles
of machine
DC Machine - Construction
17. RG,RSET
Let,
φ – useful flux per pole
Z – total number of conductors
P – number of poles
N – speed in rpm
A – number of parallel paths in armature
Flux cut by one conductor in one revolution = Pφ
N rotations in 60 seconds, Time for one revolution = 60/N
EMF induced in one conductor =
EMF induced in one parallel path =
DC Generator – EMF Equation
60
N
P
N
/
60
P
dt
d
A
Z
60
N
P