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Five problems to be noticed in using soft starter

1. The soft starter itself has no short circuit protection. In order to protect the thyristor, the fast fuse should be used. The quick fuse shall be selected according to the rated current of the soft starter. It should be noted that due to the long time of opening and breaking of low voltage circuit breaker (about 0.1s), it is not suitable for thyristor protection.

2. When the soft starter uses the motor to brake and stop, the input voltage of the motor is 0V but there is no electrical isolation between the motor and the power supply because the thyristor is not connected. Therefore, when repairing the motor or the line, the power supply must be cut off. For this reason, a circuit breaker shall be added between the soft starter and the power supply.

3. When the power of soft starter is large or the number of units is large, the high harmonic will have bad influence on the power grid and interfere with electronic equipment. When the motor starts smoothly to normal speed, the bypass contactor is closed and the soft starter is short circuited. That is, after the start-up, the high-power thyristor will no longer work, so as to eliminate the dry dyeing of high-order harmonic to the power grid and electronic equipment.

4. There are many protection functions built in the soft starter. In the specific application, the protection function should be selected or some protection functions should be disabled by programming according to the actual needs. For example, in the case of sudden power failure, the overload protection should act on and signal rather than cut off circuit.

5. The operating environment of soft starter is relatively high, so ventilation and heat dissipation should be done well. When installing, there should be a certain space under it to allow air to flow through its power module. When the rated current of soft starter is large, fan shall be used to cool down.