Why Does the Output End Should Be Added in the Frequency Converter? What is Its Role?

2021-01-11

1. The principle of adding reactor to the output of inverter

In the most common sense, something that can play the role of impedance in the circuit, we call it a reactor. The reactor in the power network is essentially a hollow coil with no permeable material. It can be arranged in three assembly forms, vertical, horizontal, and zigzag, as required. In the event of a short circuit in the power system, a large amount of short circuit current is generated. It is very difficult to maintain the dynamic and thermal stability of electrical equipment if it is not limited. Therefore, in order to meet the requirements of some circuit breaker blocking capacity, people often increase the short-circuit impedance, limit the short-circuit current, in series at the outgoing circuit breaker reactor.

2. The role of the inverter output reactor

The main reason of adding frequency converter behind output reactor is that: balance the distribution of capacitive load out of the cable, increase the short-circuit impedance of the main circuit out of the line. And can suppress the harmonics of the inverter output, to reduce the role of inverter noise.

Frequency converter low-frequency output with reactor effect ought to be better, because the waveform is worse at low frequency, and generally asynchronous motors are coaxial fan, so the heat is more severe. The reason to improve power factor of the output reactor is because the high harmonics do not do effective work, just a high-frequency clutter, so, improve the harmonics will definitely improve the power factor.

The input reactor is used to suppress the inrush voltage and inrush current, to protect the inverter, extend its service life and prevent harmonic interference, while the inverter uses the frequency conversion method of speed regulation, so during the time of speed regulation will often produce high harmonics and waveform distortion, will affect the normal use of equipment, for this reason, it is necessary to add a line reactor at the input, in order to improve the power factor of the inverter and suppress harmonic current, filter out harmonic voltage and harmonic current, improve the quality of the power grid.

The output reactor is used to extend the effective transmission distance of the inverter, effectively suppress the instantaneous high voltage generated when the IGBT module of the inverter switches, reduce the noise of the motor, reduce eddy current loss, and protect the power switching devices inside the inverter.