In 1893, Rittenhouse in the United States proposed a vacuum interrupter with a simple structure and obtained a design patent. With the progress of vacuum material smelting technology and the breakthroughs made in the research of the vacuum switch contact structure, in 1961, a vacuum circuit breaker of 15 kV and a breaking current of 12.5 kA appeared. Do you know the principle of a vacuum circuit breaker? What is its structure?
"Vacuum circuit breaker" is named because its arc-extinguishing medium and the insulation medium of the contact gap after arc-extinguishing are both high vacuum; it has the advantages of small size, light weight, suitable for frequent operation, and no maintenance during arc-extinguishing. The application in the network is relatively popular. vacuum circuit breakers are indoor power distribution devices in 3 ～ 10kV, 50Hz three-phase AC systems. For places that require no oiling, less maintenance, and frequent operations, the circuit breaker can be configured in the center cabinet, double-layer cabinet, and fixed cabinet for controlling and protecting high-voltage electrical equipment.
Vacuum circuit breaker is operating principle: when the dynamic and static contact opening under the action of the operating mechanism, the arc between the contacts, the contact surface volatilize at a high temperature steam, since the special shape is designed to contact, the current by generating a magnetic field, this magnetic field in an arc along the tangential direction of the contact surface of rapidly moving, in the shield to the portions of the metal vapor condensation, in the natural zero crossing of the arc extinguished, the dielectric strength between the contacts is a quick recovery stand up.
Compared to any other circuit breaker, its construction is very simple. Their structure is mainly divided into three parts, fixed contacts, moving contacts and an arc shield placed in the arc extinguishing chamber. The vacuum circuit breaker includes a steel arc chamber in a ceramic insulator arranged symmetrically in the center. The pressure inside the vacuum interrupter is kept below 10 ^ -4 Torr. The materials used for the current-carrying contacts play an important role in the performance of the vacuum circuit breaker. Alloys such as copper bismuth or copper chromium are ideal materials for making VCB contacts.
The housing of the vacuum circuit breaker is made of glass because the glass housing helps to check the circuit breaker from the outside after operation. If the glass changes from its original silver mirror to milky white, the crusher is losing vacuum. The fixed and movable contacts of the circuit breaker are placed inside the arc shield. The pressure in the vacuum interrupter was maintained at about 10-6 Torr when sealed. The moving contact of the circuit breaker moves 5 to 10 mm according to the operating voltage.
What industries are vacuum circuit breakers applied in? Follow us in the next article to tell you the answer.