The use of three-phase asynchronous motors is very common, in many industries, are used as a power source, Senli Motor Xiaobian today will give you a brief introduction to the three starting methods of three-phase asynchronous motors, everyone understand.
1, direct start.
If direct startThree-phase asynchronous motorThe current can reach the rated current6-7It has a greater impact on the power grid, especially in high-performance motors.
2Depressurized starting.
The depressurized starting mainly includes thermal self-starting, downgoing starting and star triangle downgoing starting. Thermal self-starting means that the motor voltage is reduced by the autotransformer, while the starting current is reduced. Generally reduced to rated voltage55%～75%Around.
The advantage is that the starting voltage can be easily changed by changing the number of taps of the autotransformer.
The disadvantage is the need to use autotransformers, high cost. The star triangle downshift refers to the method of reducing the starting current by changing the connection mode of the motor to reduce the starting current.
When starting, the relay method is used to make the motor connection form a star. At this time, the voltage of each phase of the motor drops to one-third of the original basic number, and the speed of the three-phase asynchronous motor reaches the rated speed triangle80%Around, the engine starts to run normally.
The advantage is that it saves the self-contained transformer and reduces the cost. At the same time, the wiring process is simple and the reliability is high.
The disadvantage is that the ratio of starting voltage cannot be changed, and the motor cannot be used for star connections.
3, frequency resistor start.
The starting of the frequency resistor means that when the motor starts, the frequency resistor in the main circuit is connected in series to reduce the starting current. Frequency sensitive resistors can smoothly change the starting current with little impact on the grid.
This is an ideal way to start. However, because the current high frequency sensitive resistors are inductors, a large number of electromagnetic eddy currents are generated during use, which reduces the power factor of the power grid.
The above is Senli summed up for everyoneThree-phase asynchronous motorOf course, the simplest is to start directly, but we should still choose the appropriate starting method according to the actual use of the environment.
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