With the continuous development of power electronics technology, the technology of frequency converters has become increasingly mature, and their application in industrial control enterprises has sprung up like mushrooms after rain. They are increasingly penetrating into various fields and have become an indispensable tool in various production processes, playing an increasingly positive role in improving production processes, increasing labor productivity, saving energy, and reducing labor intensity for workers.

When switching between frequency conversion and power frequency, there may be frequency conversion explosion and air circuit breaker tripping, which leads to various explanations and makes frequency conversion and power frequency switching an insurmountable threshold.

For example, some people say that "it is necessary to ensure that the phase sequence of the inverter output is consistent with the power frequency phase sequence, so that it is possible to switch in" and so on. If the phase sequence output by the frequency converter is truly consistent with the phase sequence of the power frequency, the frequency converter will still explode and the circuit breaker will still trip during the frequency to power frequency switching. Obviously, the reason is not due to any phase sequence, phase, etc. I'll tell you a simple method. Use a voltmeter to measure the voltage between the output terminal of the frequency converter and the power frequency phase line. No matter how you adjust the phase sequence, phase, or other parameters of the frequency converter output, the measurement result will be the power frequency 380V line voltage.

The voltage between the output terminal of the frequency converter and the power frequency phase line is the power frequency 380V line voltage. Can you directly switch between frequency conversion and power frequency? Can switching directly prevent the machine from exploding or tripping? So the technical secret of frequency conversion to power frequency switching is that the output terminal of the frequency converter cannot be short circuited to the power frequency. As long as the output terminal of the frequency converter is not short circuited to the power frequency, your method will definitely ensure successful switching.

How to ensure that the output terminal of the frequency converter is not short circuited to the power frequency? The method is very simple. You use contactor 1 to disconnect the output of the frequency converter from the motor, and then use contactor 2 to connect the power frequency to the motor. Use the normally closed contact of contactor 1 to connect the electromagnetic coil of contactor 2, that is, contactor 1 and contactor 2 must be interlocked. This ensures that the output terminal of the frequency converter cannot be short circuited to the power frequency, and your switching will never explode or trip again.

Precautions for operation:

1. To switch the power frequency motor, set the parking mode to free parking and avoid soft parking;

2. Cut off the contactor of the motor from the output end of the frequency converter. The control stop button and the frequency converter stop button are the same composite button, that is, when the stop button is pressed, the frequency converter stops and the contactor coil is cut off, cutting off the motor and frequency converter

3. Cut off the contactor of the motor from the output end of the frequency converter, and interlock the control start button with the frequency converter start button, that is, the frequency converter can only start after the contactor is connected to the motor;

4. The motor is connected to the contactor of the power frequency, and its coil control circuit is controlled by the normally closed contact of the contactor that cuts off the motor at the output end of the frequency converter, ensuring that the output end of the frequency converter cuts off the motor and then connects to the power frequency;

5. If the switching process is fast and accurate, that is, the shorter the time the motor runs away from the inertia of the power supply, the less the speed drop, and the less "impact" there is, the motor switches at rated current;

6. Attention should be paid to the phase sequence of the motor connected to the power frequency to ensure that the direction of rotation is consistent after the motor is switched;

7. An isolation circuit breaker should be installed from the power frequency to the motor.