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Principle of vacuum circuit breaker


The vacuum interrupter, the core component of the vacuum circuit breaker, is an electric vacuum device that uses a high vacuum degree to insulate the arc-extinguishing medium, and uses a pair of contacts sealed in the vacuum to realize the on-off function of the power circuit. When it cuts off a certain amount of current, the moment the moving and static contacts are separated, the current shrinks to a certain point or points where the contacts have just separated, resulting in a sharp increase in the resistance between the electrodes and a rapid increase in temperature until the electrode metal breaks down. Evaporate, and form a very high electric field intensity at the same time, resulting in violent electric field intensity emission and gap breakdown, resulting in a vacuum arc. When the working current is close to zero and the distance between the contacts increases, the ions of the vacuum arc quickly spread to the surroundings. After the arc current crosses zero, the medium in the contact gap changes from a conductor to an insulator quickly, so the current is broken. Due to the special structure of the contacts, an appropriate longitudinal magnetic field will be generated in the contact gap during arcing, which can make the arc evenly distributed on the contact surface and maintain a low arc voltage, so that the vacuum interrupter has a higher arc back Dielectric strength recovery speed, small arc energy and small corrosion rate. In this way, the current breaking capability and service life of the vacuum interrupter are improved.

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