The load conditions of the motor include starting, electric braking, no-load, energy breaking and stopping, as well as the duration and sequence of these stages. The working system is divided into the following 9 categories:

S1 continuous working system: the operation time under constant load is enough to achieve thermal stability.

S2 short time working system: under constant load, the motor operates at a given time which is not enough to achieve thermal stability. Then, the motor will be cut off and stopped for enough time to make the motor cool again until the temperature difference between the motor and the cooling medium is within 2K.

S3 intermittent cycle working system: operate according to a series of same working cycles, each cycle includes a period of constant load operation time and a period of energy interruption and shutdown time. In S3 working system, the starting current of each cycle has no significant effect on the temperature rise.

S4 includes intermittent cycle working system of starting: it operates according to a series of same working cycles, each cycle includes a period of starting time which has a significant impact on temperature rise, a period of constant load operation time and a period of energy interruption and shutdown time.

 S5 includes intermittent cycle working system of electric braking: it operates according to a series of same working cycles, and each cycle includes a period of starting time, a period of constant load operation time, a period of fast electric braking time and a period of shutdown time.  

S6 continuous cycle working system: operate according to a series of same working cycles, each cycle includes a period of constant load operation time and a period of no-load operation time, but no energy interruption and shutdown time.

 S7 includes the continuous cycle working system of electric braking: it operates according to a series of same working cycles, each cycle includes a starting time, a constant load operation time and a fast electric braking time, but no energy breaking and shutdown time.  

S8 includes the continuous cycle working system of variable speed and variable load: it operates according to a series of identical working cycles, each cycle includes a period of constant load operating time at a predetermined speed, and one or several periods of other constant load operating time at different speeds, but without energy interruption and shutdown time.

S9 load and speed non periodic change working system: non periodic working system of load and speed change in the allowed range. This working system includes frequent overload, which can be far more than full load.