Vacuum circuit breakers are fast-acting switches used to protect equipment from high fault currents. They have a wide range of advantages, including their efficiency and low maintenance requirements. Unlike oil or air circuit breakers, vacuum interrupters have high insulation strength and excellent arc quenching capacity. This enables them to operate in harsh environments without the need for regular refills.
The arc interruption process in vacuum circuit breakers takes place in a steel arc chamber surrounded by symmetrically placed ceramic insulators. Their performance mainly depends on the current-carrying contact materials used, such as copper-bismuth or copper-chrome alloys. The materials have excellent electrical conductivity and thermal capacity to pass usual load currents without overheating. They also have a high boiling point and low vapor pressure to diminish arc erosion.
These circuit breakers have superior arc quenching capability, as they are designed with a narrow gap and high dielectric strength. They are used in outdoor switchgear locations that are exposed to the elements. However, they may be subject to a variety of factors that affect their performance, including closing and opening bounce. A closed bounce can cause contact burnout and arc welding, while an open bounce may reduce the distance between the contacts after the arc has been interrupted. This can cause high overvoltages that affect the stability of a power network.
Vacuum circuit breakers have an exceptional arc quenching capacity. They are ideal for power distribution applications. They can be used in substations, transformers, capacitor banks and other equipment. They also provide quick and reliable disconnecting performance. They have a short gap and excellent recovery, which makes them a better choice than traditional breakers for high voltage currents. They are also lighter and smaller than air blast breakers. When the breaker operates, the moving and fixed contacts separate to form an arc between them. This arc is created by the ionization of metal vapors in the contacts. The arc can be easily quenched because the vapors are diffused in a vacuum medium. The arc has several parallel routes and rejects each other. After the arc is extinguished, the electrons, ions and metallic vapors quickly condense on the contact surfaces, which restores the dielectric strength of the contacts. This is the main reason that vacuum interrupters do not produce closing bounce and opening bounce, which can cause damage to equipment.
Vacuum circuit breakers have high reliability compared to other electrical equipment. They are simple in construction and can be built with an electric or manual operating mechanism. They are divided into three parts: the fixed contacts, the moving contacts and an arc shield located inside the arc interrupting chamber. The outer envelope of the breaker is constructed from glass so that it can be examined after the operation of the switch. If the glass turns milky from its original silvery mirror shine, then it is a sign that the breaker is losing vacuum.
The moving and fixed contacts are housed in an arc shield to prevent the deposition of metallic vapors on the inner surface of the outer insulating body. The movable contacts are moved by a motor-spring stored-energy closing mechanism that reduces the closing operating current. This feature allows the VCB to interrupt current under high di/dt-dv/dt conditions without being damaged by arc chutes or arc quenching. For the most reliable and affordable vacuum circuit breakers, Click This Link or explore our official marketplace.
