Motor Duty Cycle Ratings

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Motor Duty Cycle Ratings:

NEMA section:

  1. Duty Continue = Motor designed to working continuous without effect to temperature of winding and life time motor. Each motor that operated more than 3 hours belong to duty continue.
  1. Intermittent Duty = Motor designed to working in certain time then stop in certain time to cool, and then start again.
  1. Special = motor works in specific time. For instance, 5, 15, 60 minutes.



IEC section:

  1. S1 - Continuous Duty
Motor works at static or constant load for enough time to reach temperature equilibrium.

  1. S2 - Short Time Duty
The motor works at a constant load, but not long enough to reach temperature equilibrium. The rest periods are long enough for the motor to reach ambient temperature.

  1. S3 - Intermittent Periodic Duty
Sequential, identical run and rest cycles with constant load. Temperature equilibrium is never reached. Starting current has little effect on temperature rise.

  1. S4 - Intermittent Periodic Duty with Starting.
Sequential, identical start, run and rest cycles with constant load. Temperature equilibrium is not reached, but starting current affects temperature rise.

  1. S5 - Intermittent Periodic Duty with Electric Breaking.
Sequential, identical cycles of starting, running at constant load and running with no load. No rest periods.

  1. S6 - Continuous operation with intermittent load.
Sequential, identical cycles of running with constant load and running with no load. No rest periods.

  1. S7 - Continuous operation with electric starting.
Sequential identical cycles of starting, running at constant load and electric braking. No rest periods.

  1. S8 - Continuous operation with periodic changes in load and speed.
Sequential, identical duty cycles run at constant load and given speed, then run at other constant loads and speeds. No rest periods.

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