The final versions of the DIN and European standards are based on the IEC standard; the minimum values of the EN standard are specified in an EU regulation regarding the implementation of Directive 2005/32/EC for selected types of motors.
Comparison of efficiency classes
For example, a 4 pole 15 kW EFF1 motor with an efficiency of 91.8% is physically identical to a 4 pole IE2 motor with an efficiency of 90.6%.
The main difference between the EFF and IE classes is in the method used to determine the efficiency.
Exceptions to the classification requirement IEC 60034-30
Super Premium class IE4 for new technology
This technology is under development and was described in the draft version of the IEC 60034-30 standard and can now be found in the Annex A of the IEC 60034-31 application guide. The foreseen limits for Super Premium efficiency class IE4 are stated there for information purposes. They are expected to reduce power dissipation by up to 15% compared to class IE3.
Class IE4 applies to all types of electric motors, in particular squirrel cage induction motors and permanent magnet synchronous motors with inverter supply. These motors are generally rated by torque rather than power. The overall efficiency is determined taking into account the power dissipation in the converter and the often considerable process gains achieved with speed control. A direct comparison of motor classes IE4 and IE3 is therefore not meaningful.