At present, the switching components used in the domestic reactive power compensation capacitor switching device can be divided into three categories:
Due to the large inrush current and overvoltage generated during the switching process of the capacitor, the contacts of the contactor are sintered and the capacitor is broken down. The life of the contactor itself and the capacitor are short, which is not suitable for frequent operation, but the power consumption is low when passing through. It is more suitable for occasions where the load fluctuation is not large.
Thyristor contactless switch:
The thyristor non-contact switch switching capacitor uses the electronic switch to reflect the fast speed. It adopts the zero-crossing trigger circuit to turn on the no-inrush current and cut off the no-over voltage. However, when the switch is running, it will generate heat, and the fan needs to be cooled, and harmonics are generated at the same time. Contaminated power grid, the junction will produce a voltage drop of about one volt, its own power consumption, such as a 150KVAR capacitor cabinet, the operating thyristor consumes up to 500W. It is suitable for applications where the load fluctuation frequency is fast and the impact is relatively large, because the capacitor can be re-injected without discharging.
The composite switch connects the high withstand voltage and high current thyristor in parallel with the contact of the magnetic holding relay. Through the microcomputer control, it automatically finds the optimal input point and the best resection point, realizes the voltage zero-crossing input and the current zero-crossing cut. The breaking moment is completed by the thyristor, and the running through current is triggered by the pulse holding voltage of the magnetic holding relay to make the contacts pull in, which is low power consumption, no heat, no harmonics, safe and reliable; the switching speed is between the contactor and the thyristor Between the non-contact switches, the scope of application is large.