IE efficiency class under high voltage!

Small reminder on the efficiency classes of electric motors:

2008 was the year when the International Electrotechnical Commission standardized IE efficiency classes for low-voltage AC motors for the first time. The IEC 60034-30-1 standard normalizes IE1 to IE4 efficiency classes for motors operating with a sinusoidal voltage whose value Un is between 50 volts and 1000 volts. 2 to 8 pole motors with an assigned power between 0.12 kW and 1000 kW are concerned.

New IEC 60034-30-3 standard:

Until now, High Voltage motors (rated voltage UN > 1000 volts) were not concerned by IE efficiency classes.

This state of affairs will soon change. In March 2024, the new IEC 60034-30-3 standard will be published, which regulates IE efficiency classes for HV motors.

Subject to last-minute changes, the preparatory drafts for this standard defined the following scope of application:

• Nominal voltage greater than 1000 volts and less than or equal to 11000 volts
• Frequency: 50 and 60 Hz
• Rated power between 200 kW and 2000 kW
• Single-speed motor designed for direct start on sinusoidal voltage
• Cooling mode: IC 411, IC 511, IC 611, IC 01 and IC 81W
• Motor marked for any ambient temperature in the range between -20°C and + 60°C
• Motor marked for an altitude up to 4000 meters above sea level

The efficiency of these motors is determined from the losses for rated operation obtained by measurements according to IEC 60034-2-1.

The standard IEC 60034-30-3 will define IE1 to IE4 classes for HV motors and will impose the marking of the IE class on the nameplate.

Some motors have rated efficiencies below IE1. No marking of these motors shall be required.