Delivering the latest efficiency standards for power drive systems
By Dipl Ing FH Y Yüce, Bauer Gear Motor GmbH
Electricity +Control, September 2015 (pages 22, 23)
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Recent regulations relating to electric motor efficiency require a motor between 7,5 kW and 375 kW to use either an IE3 rated motor or an IE2 motor installed with a variable frequency drive (VFD). However, this is the minimum standard and some manufacturers continue to develop motor technology and designs to help end users maximise the potential energy savings.
While the minimum energy efficiency ratings are tightened for the majority of electric motors, there are some exceptions - namely brake motors and those operating in potentially explosive atmospheres - that will retain their exempt status. However, the company represented by the author, is leading the field with the development of the S series of Permanent Magnet Synchronous Motor (PMSM) which offers variable-speed motors in efficiency class IE4 for use in explosion hazardous areas.
Currently most Ex e (Increased Safety) rated variable speed, three-phase induction motors on the market are generally available in standard efficiency class IE1. While the efficiency of these can be improved with the addition of frequency inverters, they still fall well short in comparison to the improved design of IE3 motors.
IE4 is something many manufacturers are talking about yet few are actually delivering. There is a cost premium to these motors, but the market uptake should be driven by the economics over the life of the motor. For a small to medium sized electric motor that is running close to capacity for the majority of the time, used in a continuous manufacturing process for example, then the additional investment in terms of purchase cost is quickly outweighed by the energy savings that can be achieved.
- Lifetime costing is becoming an increasingly important consideration for any equipment.
- The efficiency of a motor drive system is based on the efficiency of the motor, as well as the mechanical system coupled to it.
- Leading geared drive manufacturers are now able to provide highly efficient combinations, and clients are urged to confirm that the systems they purchase are indeed as efficient as they claim to be.