Did you realise that electric motors are believed to be responsible for 53% of all global electricity use?1 It is no surprise then that we have seen international standards come into play over the past few decades that have required manufacturers to develop more energy efficient motors in order to reduce energy consumption and CO2 emissions.
The international IEC standard for electric motors has been in place since 2010. The IEC 60034-30-1 classification scheme identifies four levels of motor efficiency;
- IE1 - standard efficiency
- IE2 - high efficiency
- IE3 - premium efficiency
- IE4 - super premium efficiency
In Europe it has been mandatory for manufacturers to use IE3 class motors since 1st January 2015. As of yet, no date exists for the mandatory use of super premium efficiency IE4 class motors.
Classifications and legal requirements have subsequently resulted in significantly improved energy efficiency for premium class electrical motors.
End-user advantages of high efficiency motors
The use of high efficiency motors is not only better for the environments, but it also has a number of benefits for the compressed air user;
Lower operating temperatures
The internal efficiency loss caused by heat generation and friction can be as high as 20% in small motors and 4-5% in motors upward of 160 kW. IE3 and IE4 motors operate with significantly less heating and, as a result, with much lower losses. See the graph below:
IE3 and IE4 motors operate with significantly less heating and, as a result, with much lower losses.
A conventional motor with F class insulation operates at about 80 K, giving it a temperature reserve of 20 K, whereas an IE motor, working under the same operating conditions, will run at only about 65 K, increasing its reserve to 40 K.
Lower working temperatures mean less thermal stress on the motor, the motor bearings and terminals. Motor service life is significantly extended as a result.
More compressed air for less power consumption Less heat loss leads to increased efficiency. Thus, with precise matching of the compressors to the enhanced efficiency motors, air delivery can be increased and specific power can be improved. This means improved performance, shorter compressor running time and less power consumed per cubic metre of compressed air delivered.
Realising the efficiency gains for the end user, Kaeser began using IE3 motors in their rotary screw compressors in 2012 - three years before it became a mandatory requirement. And, since 2015 they have started moving towards IE4 motors, with a large range of rotary screw compressors now available as standard with IE4 motors. With the precise matching of the compressors to the enhanced efficiency motors, Kaeser Compressors has been able to achieve up to a six percent increase in air delivery and a five percent improvement in specific power!
In Australia and New Zealand a minimum E2 or E3 efficiency level is required (as per AS/NZS 1359.5) on 0.73 to 185 kW electric motors. With energy prices continuing to rise, it is therefore worth doing some research before investing in a new compressor to see what efficiency level the electric motor has. Opting for a compressor with a premium or super premium efficiency motor may certainly be one way end users could make significant savings.
1International Electrotechnical Commission: Examples by industry sector Electric motors
KAESER Kompressoren (2016): Compressed air engineering – basic principles, tips and suggestions