AC capacitor switching circuit

Abstract

The invention proposes a switching method and switching circuit of an AC capacitor. A main relay contact protection circuit is formed by a diode and an auxiliary relay in parallel at both ends of the relay contacts, and the main relay contacts are closed or broken during the conduction period of the diode. Open, there is no surge current and no contact ignition when the contacts are in action. The withstand voltage of the switching switch when it is disconnected is equivalent to that of the relay switching switch, and the misleading phenomenon of the electronic switch will not be found, and the switching speed Equivalent to thyristor switching. It has the characteristics of simple circuit, reliable operation, low cost and fast switching speed.

Description

Technical field [0001] The patent application of the present invention relates to an AC capacitor switching circuit, which belongs to the field of electrical switches, in particular to the field of electronic / mechanical composite switches. Background technique [0002] AC capacitors are widely used in grid power factor compensation and grid filtering. When used in the grid, AC capacitors must be connected or disconnected with the grid at any time according to the actual needs of the grid, which is the so-called switching of AC capacitors. At present, several schemes are commonly used, such as MSC (contactor, circuit breaker) switching, TSC (thyristor) switching, and composite switch (silicon controlled and contactor parallel switch). The disadvantage of MSC switching is that it cannot solve the impact of the surge current generated at the moment the capacitor is connected to the grid on the grid and the impact on the life of the capacitor. The current solution to the surge curren...

AI Technical Summary

Problems solved by technology

Therefore, the misconduct of the thyristor is an insurmountable problem in the TSC switching and composite switch switching schemes. TSC switching is to use a high-current thyristor to solve the problem of burning the thyristor by the surge current when the thyristor is misconducted. However, composite switches generally use silicon controlled rectifiers with small rated currents, because using silicon controlled rectifiers with large rated currents will lose the advantage of low cost of composite switches, and the misconduct of silicon controlled rectifiers is the main reason for the failure of composite switches. one

In the composite switch scheme, in order to reduce the false conduction of the thyristor, the thyristor with a higher dv / dt value is generally selected, but this only reduces the probability of false conduction of the thyristor, and cannot fundamentally solve the problem

In addition, the surge current generated by the false conduction of the thyristor also has a great impact on the life of the AC capacitor and the power grid

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