# How to realize frequency conversion in frequency converter -? Perfect switching between power frequencies-V & T

by：V&T Technologies     2019-11-11
With the continuous development of power electronics technology, the technology of frequency converters has become increasingly mature, and the application in industrial control enterprises has mushroomed and is increasingly infiltrating into various fields, it has also become an indispensable and important tool in all production links, and plays an increasingly positive role in improving production processes, improving labor productivity, saving energy, and reducing labor intensity of workers. Frequency conversion- When the power frequency is switched, a frequency conversion bomber appears, and an open trip occurs, resulting in various explanations, making the frequency conversion- Power frequency switching has become an insurmountable threshold. For example, some people say that 'the phase sequence of the inverter output must be consistent with the power frequency phase sequence, so that it is possible to cut in' and so on. If the phase sequence output by the inverter is consistent with the true phase sequence of the power frequency, the frequency conversion- When the power frequency is switched, the frequency conversion is still blown, and the air is still tripped. Obviously, the reason is by no means because of phase sequence, phase, etc. I'll tell you a simple method. You use a voltmeter to measure the voltage between the output of the inverter and the power frequency phase line, no matter how you adjust the phase sequence, phase or other output of the inverter, the measurement results are all power frequency 380V line voltages. The voltage between the output of the inverter and the power frequency phase line is the power frequency 380V line voltage, you can directly perform frequency conversion-Power frequency switching? Can Direct switching not blow up the machine or trip? So frequency conversion- The technical secret of power frequency switching is that the output of the inverter and the power frequency cannot be shorted. As long as the output of the inverter and the power frequency are not shorted, then your method will ensure that the switching is successful. How to ensure that the output of the inverter is not short-circuited to the power frequency? The method is very simple. You use a contactor 1 to disconnect the output of the inverter from the motor, then use a contactor 2 to connect the power frequency with the motor, and use the normally closed contact of the contactor 1 to connect the electromagnetic coil of the contactor 2, that is, Contactor 1 and contactor 2 must be locked. This ensures that the output of the inverter and the power frequency cannot be short-circuited, and your switching will never blow up or trip. Precautions for operation: 1. To switch the power frequency motor, the parking mode is set to free parking, and no soft parking is allowed; 2. Cut off the Contactor of the motor from the output of the inverter, and the control stop button and the inverter stop button are the same composite button, that is, when parking is pressed, the inverter stops the contactor coil and cuts off the motor and the inverter 3. The Contactor of the motor is cut off from the output of the inverter, and the control start button is interlocked with the inverter start button, that is, after the start contactor is connected to the motor, frequency conversion can start; 4. The motor is connected to the power frequency contactor, and its coil control is routed back to the normally closed contact control of the Contactor of the inverter output to cut off the motor, ensuring that the inverter output is connected to the power frequency after cutting off the motor; 5. If the switching process is fast and accurate, that is, the shorter the motor runs out of the power supply inertia, the less the speed drops, and the less 'impact' exists, the motor switches under the rated current; 6. Attention should be paid here to the phase sequence of the motor connected to the power frequency to ensure consistent steering after the motor is switched; 7, power frequency to the motor should be equipped with an isolation circuit breaker.
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