Analysis of efficient arc extinguishing mechanism in high voltage direct current contactor

In the power system, high voltage direct current contactors play a vital role. They are responsible for connecting and disconnecting the circuit in the high-voltage DC circuit. However, when the contactor disconnects the high-voltage DC circuit, a continuous arc is often generated due to the instantaneous interruption of the current. The existence of the arc will not only cause serious thermal damage to the contacts and internal structure of the contactor, but may also cause safety hazards such as short circuit and fire, seriously affecting the stable operation of the power system. Therefore, in order to ensure that the high voltage direct current contactor does not generate a continuous arc when disconnecting the circuit, engineers have designed a variety of efficient arc extinguishing mechanisms.

1. Mechanical arc extinguishing method
The mechanical arc extinguishing method is one of the most commonly used arc extinguishing methods in high voltage direct current contactors. It mainly changes the shape and path of the arc by physical means to achieve the purpose of extinguishing the arc.

Magnetic blow-out arc extinguishing: Magnetic blow-out arc extinguishing is a method of using a magnetic field to generate a force on the arc. In a high voltage direct current contactor, when the contacts separate and an arc is generated, a strong magnetic field is generated by a built-in magnetic field generating device. This magnetic field will produce a fast moving force along a specific path on the arc, causing the arc to elongate and cool rapidly under the action of the magnetic field. The surface area of ​​the elongated arc increases, the heat dissipation speed is accelerated, and the arc temperature drops rapidly, finally achieving the effect of extinguishing the arc. The magnetic blowout arc extinguishing method has the characteristics of strong adaptability and good arc extinguishing effect, and is suitable for a variety of currents and environmental conditions.

Grid arc extinguishing: Grid arc extinguishing hinders the development of the arc by setting a metal grid between the contacts. When the arc is generated, it passes through the grid. Due to the obstruction of the grid, the arc is divided into multiple small segments during the crossing process, and the arc energy is dispersed. At the same time, the cooling effect of the grid causes the arc temperature to drop rapidly and the arc is extinguished quickly. The grid arc extinguishing method has a simple structure and is easy to maintain. It is one of the commonly used arc extinguishing methods for high voltage direct current contactors.

Spring arc extinguishing: Spring arc extinguishing uses the elastic force of the spring to elongate the arc so that the arc heat is gradually dissipated. However, since the effect of spring arc extinguishing is relatively poor and it is easy to cause the arc to reignite, it is usually used in combination with other arc extinguishing methods. In high voltage direct current contactors, spring arc extinguishing is usually used as an auxiliary arc extinguishing method to further improve the arc extinguishing effect.

Air blowing arc extinguishing: Air blowing arc extinguishing uses compressed air or other gases to blow the arc to quickly dissipate the heat of the arc. This method is suitable for low-voltage and low-current occasions. In high voltage direct current contactors, air blowing arc extinguishing is usually used as an arc extinguishing method in special occasions, and the gas source needs to be maintained regularly.

2. Other arc extinguishing mechanisms
In addition to mechanical arc extinguishing methods, high voltage direct current contactors also use a variety of other arc extinguishing mechanisms, such as vacuum arc extinguishing and gas medium arc extinguishing. Vacuum arc extinguishing disconnects the circuit in a vacuum environment and uses the insulation properties of the vacuum to extinguish the arc. Gas medium arc extinguishing uses the insulation and arc extinguishing properties of specific gases (such as SF6) to extinguish the arc. These arc extinguishing mechanisms are also widely used in high voltage direct current contactors.