Air and vacuum circuit breakers are among the commonly used devices for additional safety when operating an electrical circuit. Air circuit breakers are typically used in low voltage applications (i.e. less than 660 volts), and vacuum circuit breakers can handle higher voltages at up to 15KV or more. Both are compact, but the vacuum circuit breaker tends to be smaller and occupies less space. Here is an overview of the two and their respective applications:
- Air circuit breaker
This type of circuit breaker operates at atmospheric pressure in air, which acts as the arc-quenching medium. It extinguishes the arc by blowing air through the area where the arc is formed when a load is interrupted. The extinguished arc is in the chute where it will dissipate. An air circuit breaker may be the best option when the frequent operation is needed due to the minimal arc energy. It provides fast arc quenching, with the duration of the arc being similar for all current values.
- Vacuum circuit breaker
This circuit breaker suppresses the formation of the arc by keeping a vacuum in the chamber where the arc occurs. That way, no air will ionize and carry that arc. In a VCB, arc quenching occurs in a vacuum chamber known as the 'vacuum interrupter', which is made up of a steel arc chamber in the heart of strategically arranged ceramic insulators. CuCr is the best material for making VCB contacts to carry current. Vacuum circuit breakers are known for their longer service life compared to other kinds of circuit breakers. They do not have any fire hazard, too, unlike with oil circuit breakers. Likewise, they are environmentally friendly and easier to use.
Newly designed vacuum circuit breakers come with a vacuum interrupter, which the arc switches over from diffusion to a constricted state when the arc is subject to an axial magnetic field. The field can be initiated by making the arc current go through the coil outside the vacuum chamber.