1. Where it is required to reduce the starting current of the motor.
2. During normal operation, the motor does not need to have a speed regulation function, and only solves the working state of the starting process.
3. During normal operation, the load is not allowed to step down or slow down.
4. If the power of the motor is larger than 100kw, it will have a bad influence on the operation of the main transformer during starting.
5. The operation of the motor has strict requirements on the grid voltage, and the voltage drop is not more than 10%U.
6. The starting shock of the equipment is not allowed.
7. The starting torque of the equipment is not large, and it can be started with no load or light load.
8. Medium and large motors need energy-saving starting. From the initial investment point of view, it is more economical to use auto-coupling step-down starting for motors with a power below 75KW, and it is more cost-effective to use a soft starter for motors with a power of 90-250kw.
9. Machinery for short-term repetitive work. This refers to machinery with long-term no-load (light load less than 35%) short-term heavy load and high no-load rate, or machinery with low load duration rate, such as cranes, belt conveyors, metal material calenders, lathes, punches, Planers, shears, etc.
10. Work machines with functions such as sudden jump, smooth acceleration, smooth deceleration, quick stop, low-speed braking, and accurate positioning are required.
11. Motors with long-term high speed and short-term low speed. When the load rate is lower than 35%, the soft starter has better energy saving effect.
12. There are multiple motors and these motors do not need to be started at the same time.
13. The occasions where the motor is not allowed to shut down instantly. Such as high-rise buildings and other water pump systems, if they stop instantaneously, there will be a huge water hammer effect, and the pipeline or even the water pump will be damaged.
14. It is especially suitable for all kinds of pump or fan loads that need soft start and soft stop.
15. For high-voltage/medium-voltage asynchronous motors, soft starters or frequency converters can be used. The investment of a step-down transformer-low-voltage inverter-step-up transformer is 2-4 times more than that of a soft starter. Generally speaking, for loads with starting torque less than 50%, a soft starter should be used; for loads with starting torque greater than 50%, a frequency converter should be used.
16. Occasions where it is necessary to easily adjust the starting characteristics.