ENERGY EFFICIENT INDUCTION MOTORS By JINTU GEORGE Edited By Sarath S Nair

contents  Introduction  Energy efficient motor  Specification of eem  Motor losses & reduction method  Benefits of implementing eem  Equivalent circuit  Experimental setup  Operating & performance characteristic  Eem in Indian scenario  Advantages  Application  conclusion

Introduction  A large fraction of electrical energy consumed in many facilities is used to run electric motors. Nationally, motor driven systems account for about 57% of all electrical energy use.  The electric motor manufacturers are seeking methods for improving the motor efficiencies, which resulted in a new generation of electric motors that are known as energy efficient motors.  This paper deals with energy conservation by installing energy efficient motor (EEM) instead of standard efficiency motor.

Energy efficient motors  It produces same shaft output power but uses less electrical input power than a standard efficiency motor.  Standard motor generally competes on price, not efficiency, but EEM competes on efficiency, not price.  Both single phase and three-phase motors available.  EEM are higher quality motors with longer warranty.  20 year life span

Eem specifications  to make it much easier for purchasers to identify energy efficient motors on the market.  motor efficiency classification labels – Eff1, Eff2 & Eff3.  The programme was implemented by a voluntary agreement between the Commission and the motor manufacturers to reduce sales of Eff3 motors by half.

Motor losses & reduction Techniques

 Core loss represents energy required to magnetize the core material (hysteresis) and includes losses due to creation of eddy currents that flow in the core.  Windage and friction losses occur due to bearing friction and air resistance.  Stator losses appear as heating due to current flow (I) through the resistance (R) of the stator winding. This is commonly referred to as an I2R loss.  Rotor losses appear as I2R heating in the rotor winding.  Stray load losses are the result of leakage fluxes induced by load currents.

High efficiency motor design  Improved steel:  Thinner laminations:  Increasing conductor's volume:  Modified slot design:  Narrowing airgap:  Improved rotor insulation :  More efficient fan design :

Benefits of implementing eem systems  Electricity savings potential  Environmental benefits  Micro economical benefits  Macro economical benefits

Induction motor equivalent circuits in d-q coordinates

Experimental setup

Differerent tests for analysing the performance  a) Temperature test: The motor is loaded and allowed to run until its temperature stabilizes. The temperature and winding resistances are recorded.  b) Load test: The motor is loaded at six different loading points ranging from 25%-150% of rated load. The stator and rotor copper losses are calculated from this.  c) No-load test: The motor is run at no-load with a varying supply. The friction & windage and core losses are calculated voltage between 125% to 20% of rated voltage from this.

Operating and performance characteristics of sm& eem

Constructional features of eef  rotor design - One major consideration in the design of high efficiency induction motors is to reduce rotor resistance. -efficiency can be achieved by substituting Aluminum with copper.

Energy Efficient Machine Design by Proper Selection of Core Material  core loss in a machine is around 30~ 50% of the total losses.  reduction of core material thickness and stress relief annealing of the core improved machine efficiency.

Efficiency Improvement by Insertion of Superconducting Materials  High temperature superconductors (HTS), which offered the advantage of cooling via liquid nitrogen instead of liquid helium.  complete elimination of refrigerator power consumption would only show an improvement in machine efficiency of ~0.02% for a 300 MVA rating.  Of more importance than the ef ficiency improvement is that use of a liquid nitrogen ambient would lead to reduced capital costs for the refrigeration plant and reduce the complexity of the cryogenic design.

Rotor with two end rings

Power factor improvement in IM  Installing external capacitor  Avoid operation of equipment above its rated speed  Replacement of SM with EEF.

How energy efficient motor differ from standard motor ???...  Higher quality and thinner steel laminations in the stator  More copper in the windings  Smaller air gap between the rotor and stator  Reduced fan losses  Closer machining tolerances  Generally, they cost 15 to 30 percent more than standard motors, depending on the specific motor, manufacturer, and market competition

Eem recognition in indian scenario  Siemens India awarded prestigious “BEE Star” rating for their energy-efficient motors Siemens motors help customers minimize their energy consumption in production, thus significantly reducing their operating costs and the cost of ownership and bringing about a significant boost to productivity.

Advantages:  - The EEM has a greater efficiency than a standard motors; therefore they have less operating costs.  - EEM has a lower slip so they have a higher speed than standard motors.  - EEM can reduce maintenance costs and improve operations in industry due to robustness and reliability.  - Increasing the productivity.

Summary  Energy efficient motors, their specifications are discussed.  Constructional difference from standard motor & the method of achieving high efficiency is also discussed  Different test methods, operating & performance characteristics according to the test result are also discussed

References [1] “Understanding Energy Efficiency Motors”, Electrical Apparatus Service Association (EASA), pp [2] D.G. Walters, I.J. Williams, D.C. Jackson, B. Hansen “The case for a new generation of high efficiency motors – Some problems and solutions”, Electrical Machines and Drives,11-13 Sept. 1995, Conference Publication No. 412, IEE [3] "Understanding high efficiency motors," Published by copper development centre, 2001 [4] J. Andreas, Energy Efficient Electric Motors: Selection and Application, Marcel Deker, 1992.

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