Answer about the working system of electric motors

Interpretation of Motor Working System

The working system of the motor indicates the allowable cycle time of the motor under different loads. The classification of the working system of a motor is an explanation of the load that the motor can withstand, including starting, electric braking, no-load, power-off, and the duration and sequence of these stages. The working system is divided into 10 categories.

(1) Continuous operation, S1. Continuous operation S1 is a type of operation with a constant load, and its duration is sufficient to achieve thermal equilibrium.

(2) Short term operation, S2. Short term operation refers to running with a load for a very short period of time, to the point where thermal equilibrium cannot be achieved. The interval (without applying voltage to the motor) is very long, which actually lowers the temperature of the motor to the temperature of the cooling medium. The recommended duration for short-term operation is 10 minutes, 30 minutes, 60 minutes, and 90 minutes.

(3) Intermittent operation that has no effect on temperature during startup, S3. Intermittent operation S3 involves a continuous sequence of operations with the same time interval. Each interval includes a constant load time and an intermittent time. These times, whether it is load time or cooling time, are not sufficient to reach thermal equilibrium within this time interval, and it is assumed that the peak current at start-up has no significant effect on heating.

(4) Intermittent operation that affects temperature during start-up, S4. Intermittent operation S4 involves a continuous sequence of operations with the same time interval. Each interval includes a start-up time, a constant load time, and an intermittent time. These times are not enough to reach thermal equilibrium within this time interval. In this operation, the motor either stops naturally after a power outage or is braked by a mechanical brake, so the winding produces almost no additional heat.

(5) Intermittent operation that affects temperature during start-up and braking, S5. Intermittent operation S5 involves a continuous sequence of operations with the same time interval. Each interval includes starting time, time with constant load, braking time, and intermittent time. These times are not sufficient to reach thermal equilibrium within that time interval. In this operation, braking is achieved by electricity (e.g. reverse current).

(6) Continuous operation with intermittent load, S6. Continuous operation S6 involves the operation composed of continuous sequences with the same time interval. Each interval includes time with constant load and idle time. These times, whether under load or cooling, are not sufficient to reach thermal equilibrium within that time interval.

(7) Uninterrupted operation with starting and braking, S7. Uninterrupted operation S7 involves a continuous sequence of operations with the same time interval. Each interval includes a start-up time, a time with constant load, and an electric braking (such as through reverse current) time. These times are not sufficient to reach thermal equilibrium within that time interval. This operation does not stop, and the motor is actually constantly under the action of voltage.

(8) Uninterrupted operation with variable speed, S8. Uninterrupted operation refers to the operation composed of continuous sequences with the same time interval. Each interval includes a constant load time with one of its corresponding speeds and a constant load time directly connected to it with other speeds. Variable pole asynchronous motor is an example of this operating mode.

(9) S9 working system with non periodic changes in load and speed. Under this working system, the load and speed undergo non periodic changes within the allowable range, including frequent overloads, whose values can far exceed the reference load.

(10) Discrete constant load and speed working system S10. This work schedule includes a specific number of discrete loads (or equivalent loads)/speeds (if possible), and each load/speed combination should have sufficient operating time to achieve thermal stability of the motor. The minimum load value in a work cycle can be zero (no load or shutdown and energy interruption).