Efficiency class
The International Electrotechnical Commission (IEC) has developed an internationally applicable testing Standard IEC 60034-2-1 for electric motors and a classification scheme IEC 60034-30-1 with four levels of motor efficiency ("IE-code")1:
- IE1 Standard efficiency,
- IE2 High efficiency,
- IE3 Premium efficiency
- IE4 Super premium efficiency.
The IE-code and its efficiency levels create a basic vocabulary for governments to determine the efficiency level for their minimum energy performance standards (MEPS). The European Union sets motor MEPS levels (Directive 640/2009) at IE3 (or IE2 in combination with a variable frequency drive) from 2015 for smaller motors and from 2017 covering also larger motors.
Fig.1. Cut-away of standard, energy-efficient, and premium efficiency motors. 2
Efficiency value for a certain class depends on power as shown on the diagram below 3:
Efficiency at partial load (e.g. 25%, 50%) is lower than at rated load (100%). High efficiency class motors are larger and heavier, while lower IE class motors are more compact and lighter. Therefore, motors with higher IE class are more expensive.
1 Source: IEC 2 Source: photo from Toshiba International Corporation, "Premium efficiency motor selection and application guide. A handbook for industry by US department of Energy". 3 Source: Elvem