What IE Classes Define
IE stands for International Efficiency. The IEC 60034-30-1 standard specifies the minimum efficiency that a three-phase induction motor must achieve at rated load, rated voltage, and rated frequency in order to be classified—ranging from IE1 (Standard Efficiency) to IE5 (Ultra-Premium Efficiency). The η value specified on the nameplate is the actual guaranteed efficiency of this motor and may exceed the class minimum.
| IE class | η bei 11 kW | EU Status 2026 |
|---|---|---|
| IE1 | 87.6 % | No longer marketable in the EU |
| IE2 | 89.8 % | Only values below 0.75 kW are permitted |
| IE3 | 91.4 % | Mandatory 0.75—1,000 kW (as of 07/2021) |
| IE4 | 93.3 % | Mandatory 75–200 kW (as of 07/2023) |
| IE5 | 95.0 % | Not an EU requirement; voluntary (PMSM) |
Description and values of the figure
The IE3 bar is highlighted because this class has been mandatory in the EU for most industrial motors since 2021. IE4 (hatched) has been mandatory since 2023 only for the 75–200 kW power range; IE5 (dashed) is currently voluntary and is usually achievable only with permanent magnet synchronous motors. The exact numerical values are also listed in the table above this figure.
| Name | Value (%) |
|---|---|
| IE1 | 87.6 |
| IE2 | 89.8 |
| IE3 | EU requirement since July 2021 |
| IE4 | 93.3 |
| IE5 | 95.0 |
Worked Example: The Energy Cost of Efficiency
For the same output power, a motor with lower efficiency consumes more electrical power. For an 11-kW motor with 6,000 operating hours per year at full load:
IE3 (η = 91.4 %): P_ein = 11/0.914 ≈ 12.04 kW (calculated using unrounded values) → Annual energy ≈ 72,210 kWh
IE4 (η = 93.3 %): P_ein = 11/0.933 ≈ 11.79 kW (calculated using unrounded values) → Annual energy ≈ 70,740 kWh
Switching from IE3 to IE4 saves approximately 1,470 kWh per year for this motor. The more operating hours the motor runs per year, the faster the additional cost of an IE4 motor pays for itself; the calculation depends on the actual additional cost and the price of electricity.
Partial Load: Induction Motor vs. Permanent-Magnet Synchronous Motor
The IE class is determined exclusively at 100% rated load—but many drives operate continuously in the partial-load range. In this range, the technologies behave differently: An induction motor (ASM) experiences a disproportionately large loss in efficiency below 50% load because rotor slip losses have a relatively greater impact. A permanent magnet synchronous motor (PMSM) exhibits a significantly flatter efficiency curve in the partial-load range thanks to the absence of rotor slip losses. The extent of the difference in individual cases is a guideline and depends heavily on the motor size and speed—the part-load characteristic curve in the manufacturer’s data sheet is the authoritative reference. A common misconception: A frequency inverter makes system operation more efficient, but it does not replace the motor’s efficiency class itself.
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