Why is an reactor added to the reactive power compensation capacitor cabinet?

The function of the reactive power compensation cabinet is to improve the power factor, reduce line losses, and increase the utilization margin of the transformer. The role of the inductor connected in series at the front end of the capacitor is to prevent the capacitor and the power supply system from experiencing series or parallel resonance, which could cause the harmonics to be amplified and lead to overcurrent in the capacitor and its damage. Additionally, the series inductor can also play a role in limiting the inrush current.

There are two types of reactors: current-limiting reactors and harmonic reactors. In the past, current-limiting reactors were combined with ordinary contactors. Now, there are special contactors specifically for switching capacitors, and generally, current-limiting reactors are no longer necessary. When the system has a large amount of harmonics, harmonic reactors should be added. At this time, capacitors should use dehumidifying capacitors to form a static compensation and harmonic filtering device. Generally, to reduce the response time, dynamic compensation and dehumidifying devices are now mostly used. When the load contains a large amount of harmonics (such as with welding machines, electric furnaces, etc.), a filtering reactor must be added, and the filtering reactor should match the harmonic frequency in the system (such as 5.67% reactance if the main harmonics are 5th and 7th). At this time, the rated voltage of the power capacitor should be selected at a higher level.

In the capacitor compensation cabinet, reactors are installed for two purposes:

1.Limit the inrush current when the capacitor is engaged.
2. In systems with a large amount of harmonic current, series reactors can prevent the harmonic current from undergoing resonance amplification, which is known as a "de-resonant" capacitor cabinet.

If a dedicated contactor for capacitor switching is used, the issue of closing surge current should be considered. This has now largely been replaced by thyristor switching switches. In situations where there is rapid change (with rapid load variations), a dynamic switching method can be adopted. If the aim is to suppress harmonic resonance, the reactance rate should be determined based on the main components of the background harmonics in the distribution system at the point where the parallel capacitor bank is connected.

Jinneng Electrical is a well-known manufacturer of reactive power compensation devices, and also provides one-stop capacitor cabinet renovation solutions. The main products include: capacitors, reactors, thyristor switching modules, reactive power controllers, low-voltage reactive power compensation complete sets, active power filters, static reactive power generators, and harmonic protectors, etc.