Starting mode of high voltage motor

It is to start the motor directly at full voltage. If the power grid conditions permit, direct start-up can be adopted. However, in the actual production process, due to the limited capacity of the power grid, direct start-up is rarely used. When using direct starting, the no-load starting current will reach 4 ~ 7 times of the rated current, which will greatly reduce the voltage, have a great impact on the power supply system, and even destroy the normal operation of other equipment in the same power grid. If the voltage drop exceeds a certain value, it may cause the superior substation to trip. Moreover, the impact of large current is great, which will cause motor failure and shorten the life of the motor. Therefore, this direct start mode is rarely used in actual operation.

2. Start the autotransformer.

That is, when the motor starts, the voltage is reduced through the middle plug of the optional autotransformer. When the motor runs stably or the current reaches a certain value, the autotransformer is cut off and enters the normal operation mode. The starting current of autotransformer is relatively small (about 3 times the rated current), but there is a secondary impact, which has a certain impact on power grid and motor.

3, inverter soft start

In the whole starting process, the motor will not have overcurrent, and the starting torque is large and the starting performance is good. However, the frequency conversion device is expensive, and the circuit principle of the frequency conversion device is complex, with many faults, which requires high maintenance technical level.

4, thyristor series soft start

The soft start of frequency converter will not have overcurrent during the whole starting process, and will not have impact on power grid and motor. However, the thyristor is easy to be damaged and the cost of spare parts is high.