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Electrical motors 4to medio.ppt
This document provides an overview of electric motors used in industry. It begins with an introduction that defines electric motors and notes they account for 70% of industrial electrical load. It then outlines the training agenda which will cover motor types, assessment, and efficiency opportunities. The document proceeds to describe the different types of electric motors including alternating current motors like induction and synchronous, as well as direct current motors. It provides details on motor components, operation, and classifications. Finally, it discusses factors that influence motor efficiency and how motors lose energy while serving a load.
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Electrical motors 4to medio.ppt
- 1. 1 Training Session onEnergy Equipment Electric Motors Presentation from the “Energy Efficiency Guide for Industry in Asia” www.energyefficiencyasia.org
- 2. 2 © UNEP 2006 TrainingAgenda: Electric Motors Introduction Types of electric motors Assessment of electric motors Energy efficiency opportunities
- 3. 3 © UNEP 2006 Introduction •Electromechanical device that converts electrical energy to mechanical energy • Mechanical energy used to e.g. • Rotate pump impeller, fan, blower • Drive compressors • Lift materials • Motors in industry: 70% of electrical load What is an Electric Motor?
- 4. 4 © UNEP 2006 Introduction HowDoes an Electric Motor Work? (Nave, 2005) 1 2 3 4
- 5. 5 © UNEP 2006 Introduction Threetypes of Motor Load Motor loads Description Examples Constant torque loads Output power varies but torque is constant Conveyors, rotary kilns, constant-displacement pumps Variable torque loads Torque varies with square of operation speed Centrifugal pumps, fans Constant power loads Torque changes inversely with speed Machine tools
- 6. 6 © UNEP 2006 TrainingAgenda: Electric Motors Introduction Types of electric motors Assessment of electric motors Energy efficiency opportunities
- 7. 7 © UNEP 2006 Typeof Electric Motors Classification of Motors Electric Motors Alternating Current (AC) Motors Direct Current (DC) Motors Synchronous Induction Three-Phase Single-Phase Self Excited Separately Excited Series Shunt Compound
- 8. 8 © UNEP 2006 Typeof Electric Motors • Field pole • North pole and south pole • Receive electricity to form magnetic field • Armature • Cylinder between the poles • Electromagnet when current goes through • Linked to drive shaft to drive the load • Commutator • Overturns current direction in armature DC Motors – Components (Direct Industry, 1995)
- 9. 9 © UNEP 2006 Typeof Electric Motors • Speed control without impact power supply quality • Changing armature voltage • Changing field current • Restricted use • Few low/medium speed applications • Clean, non-hazardous areas • Expensive compared to AC motors DC motors
- 10. 10 © UNEP 2006 Typeof Electric Motors Classification of Motors Electric Motors Alternating Current (AC) Motors Direct Current (DC) Motors Synchronous Induction Three-Phase Single-Phase Self Excited Separately Excited Series Shunt Compound
- 11. 11 © UNEP 2006 Typeof Electric Motors • Electrical current reverses direction • Two parts: stator and rotor • Stator: stationary electrical component • Rotor: rotates the motor shaft • Speed difficult to control • Two types • Synchronous motor • Induction motor AC Motors (Integrated Publishing, 2003)
- 12. 12 © UNEP 2006 Typeof Electric Motors • Constant speed fixed by system frequency • DC for excitation and low starting torque: suited for low load applications • Can improve power factor: suited for high electricity use systems • Synchronous speed (Ns): AC Motors – Synchronous motor Ns = 120 f / P F = supply frequency P = number of poles
- 13. 13 © UNEP 2006 Typeof Electric Motors • Most common motors in industry • Advantages: • Simple design • Inexpensive • High power to weight ratio • Easy to maintain • Direct connection to AC power source AC Motors – Induction motor
- 14. 14 © UNEP 2006 Typeof Electric Motors Components • Rotor • Squirrel cage: conducting bars in parallel slots • Wound rotor: 3-phase, double-layer, distributed winding AC Motors – Induction motor • Stator • Stampings with slots to carry 3-phase windings • Wound for definite number of poles (Automated Buildings)
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- 16. 16 © UNEP 2006 Typeof Electric Motors AC Motors – Induction motor How induction motors work • Electricity supplied to stator • Magnetic field generated that moves around rotor • Current induced in rotor Electromagnetics Stator Rotor • Rotor produces second magnetic field that opposes stator magnetic field • Rotor begins to rotate (Reliance)
- 17. 17 © UNEP 2006 Typeof Electric Motors AC Motors – Induction motor • Single-phase induction motor • One stator winding • Single-phase power supply • Squirrel cage rotor • Require device to start motor • 3 to 4 HP applications • Household appliances: fans, washing machines, dryers
- 18. 18 © UNEP 2006 Typeof Electric Motors AC Motors – Induction motor • Three-phase induction motor • Three-phase supply produces magnetic field • Squirrel cage or wound rotor • Self-starting • High power capabilities • 1/3 to hundreds HP applications: pumps, compressors, conveyor belts, grinders • 70% of motors in industry!
- 19. 19 © UNEP 2006 Typeof Electric Motors AC Motors – Induction motor Speed and slip • Motor never runs at synchronous speed but lower “base speed” • Difference is “slip” • Install slip ring to avoid this • Calculate % slip: % Slip = Ns – Nb x 100 Ns Ns = synchronous speed in RPM Nb = base speed in RPM
- 20. 20 © UNEP 2006 Assessmentof Electric Motors Motors loose energy when serving a load • Fixed loss • Rotor loss • Stator loss • Friction and rewinding • Stray load loss Efficiency of Electric Motors (US DOE)
- 21. 21 © UNEP 2006 Factorsthat influence efficiency • Age • Capacity • Speed • Type • Temperature • Rewinding • Load Efficiency of Electric Motors Assessment of Electric Motors
- 22. 22 Training Session onEnergy Equipment Electric Motors THANK YOU FOR YOUR ATTENTION © UNEP 2006