Chinese
With the rapid development of power electronics technology, AC variable frequency speed regulation has become the mainstream of electrical transmission since the 1990s, and its application scope is increasingly wide. However, due to the use of frequency converters in various electrical environments, if appropriate protective measures are not taken, it will affect the stability and reliability of frequency converter operation. Practice has proven that appropriately selecting reactors and using them in conjunction with frequency converters can effectively prevent the impact of overvoltage and surge current caused by operating AC incoming switches, while also reducing the harmonic pollution of the power grid caused by frequency converters and improving their power factor.
There are three types of reactors used in conjunction with frequency converters:
1. Incoming reactor
Also known as input reactor or power coordination reactor, it can limit the current surge caused by sudden changes in grid voltage and operating overvoltage, effectively protecting the frequency converter; It can not only prevent interference from the power grid, but also reduce the pollution of harmonic currents generated by rectification units to the power grid and improve its power factor.
2. DC reactor
The DC reactor is connected between the DC rectification section and the inverter section of the frequency conversion system. The DC reactor can make the inverter section operate more stably and improve the power factor of the frequency converter. In a frequency conversion system with a DC link, connecting a DC reactor after the rectifier can effectively improve the power factor. With proper coordination, the power factor can be increased to 0.95. In addition, the DC reactor can ensure stable operation of the inverter and limit short-circuit current.
3. Output reactor
When the length of the cable from the output end of the frequency converter to the motor is greater than the specified value of the product, an output reactor should be added to compensate for the charging and discharging effects of the coupling capacitance during the operation of the long cable of the motor, avoid overcurrent of the frequency converter, and suppress the harmonic output of the frequency converter, thus reducing the noise of the frequency converter. Some manufacturers also provide the maximum allowable length of the wire connecting the motor with and without an output reactor.