Operating modes according to IEC 60034

The rated power is always related to an operating mode and cyclic duration factor.

According to IEC standard 60034-1 "Rotating electrical machines - Part 1: Rating and operating behavior", the electrical operating modes are defined using time, load, and temperatures as follows:

S1 continuous duty

Operation at a constant load, with a duration long enough for the machine to reach a steady-state thermal condition.

S2 short-time duty

Operation at a constant load for a time which is less than the time required for reaching a steady-state thermal condition. The subsequent time in idle state when the windings are de-energized is long enough for the machine temperature to deviate less than 2 K from the temperature of the coolant.

S3 intermittent duty

Duty that is a sequence of identical duty cycles, with each cycle including a period of operation at constant load and an idling time with de-energized windings. The starting current does not have any significant effect on the overtemperature.

S9 operation with non-periodic load and rotational speed changes

Operation with non-periodic changes in load and speed within the permitted operating range. In this duty cycle, overloads occur that significantly exceed the reference load.