There are eight type of duty type for these series motors ,S2, S3, S4, S5, S6, S7, S8, and S9, The basic duty type is S3—40％, Cduty type is S3 cyclic duration factor is 40％, each cycle is (10min), The following duty types are most useful for these series motors.

1. Short times duty type (S2)
Operation of constlant load dring a given time, less than that required to reach themal equilibrium followed by a rest and de-energized period of sufticent duration to re-establish machine temperature withir 2 deg K of the coolant (sec figl).

2. Intermittent periodic duty type (S3)
A sequerce of identical duty cycles, each including a period of operation at constant oad and a rest and de-energized period (see fig2) but the operation period are so short that it is not sufficinet for the machine to reach themnl equilibriun in this duty type, the cycle is such that the starting current does not significanten affect the temprature rise.

3．Intermittent periodic duty type with starting (S4)
A sequence of identicae duty cycles, each including a sisnificnnt period of starting, a period of oreration of constant load and a rest and de-energized period (see fig3), but the operation periodsare so short that it is not sufficient for the machine to reach thermal equilibrium.

4． Intermittent period duty type with electric braking (S5)
A sequence of identica duty cycles, each consisting of a period of starting a period of operation at constant coad and a rest and de –energized period, but the opertion period are so short that it is not sufficient for the machine to reach thermal equilibrium (see fig4), but the operation periodsare so short that it is not sufficient for the machine to reach thermal equilibrium.