Used Circuit breakers are electrical switches designed to disrupt current in order to prevent damage to equipment, and can break circuits either regularly or irregularly.

They can also interrupt circuits with clock-like precision, disconnecting and de-energizing equipment as soon as thresholds are exceeded. Air Circuit breakers use vacuum isolation to separate their current-carrying contacts for maximum insulating strength and superior arc quenching properties.

Vacuum Circuit Breakers

Vacuum circuit breakers (VCBs) utilize vacuum medium to quickly extinguish an electric arc when two contacts become separated due to unwanted conditions. Compared to oil or SF6, vacuum has superior insulating properties and can interrupt current with extremely small contact gaps while quickly extinguishing any arcs that might exist, thus minimizing re-strike potential.

Vacuum interruption occurs when movable and fixed contacts separate under unexpected conditions, such as overloading or short-circuiting. Ionisation of metal ions leads to the formation of arcs which vaporise metal and discharge electrons onto contact surfaces causing vacuum interruptions.

The rate at which this vapor is released depends on current. When current decreases, so too does vapor density and density levels gradually fall as dielectric strength returns to the medium; eventually arcing ends when pressure reaches zero.

Vacuum circuit breakers consist of a vacuum interrupter chamber, current terminals, control element & electromagnetic actuator. They are used for switching applications like reactor switching, capacitor bank switching & transformer switching in high & medium voltage power systems. Vacuum circuit breakers have excellent fault current handling capability up to 100kA; excellent arc quenching capability up to 33kV; long life expectancies with minimal maintenance needs; but their main drawback lies in not being compatible with higher voltages due to multiple vacuum chambers being needed. Used  Circuit breaker for sale at surplusrecord.

Plain Circuit Breakers

Plain Circuit Breakers have long been used as an alternative to fuses in homes, and they feature an internal mechanism which detects over current flow and opens its contacts accordingly. This safeguard helps avoid heating of wires in your home as well as protecting appliances from excessive current flows. These types of circuit breakers are typically found in household/commercial appliances, transportation, marine and telecommunication applications.

An Arc Chute acts as an insulating barrier, confining any arc that occurs when contacts open, which can produce heat which could potentially result in fires or electrical accidents. When this arc begins, it must be quenched with either vacuum, oil, air pressure or pressurized air so as to protect contacts and avoid burning out prematurely Air Circuit molded breakers  perform two major functions. First, they absorb fault current until it can be recovered in the power system, while also protecting against short circuits and overloads. Their short-circuit breaking capacity (rms value of peak current that they can carry for specific recovery voltage conditions).

Magnetic Blowout Circuit Breakers

Magnetic circuit breakers utilize electromagnets to trip their mechanism. These devices operate differently from thermal breakers in that they respond to excessive current flow by loading apart their contacts instead of producing heat that causes bimetallic strips to expand unequally, disengaging contacts through heat-generating blowout coils and expanding to separate them mechanically before disengaging contacts using springs or compressed air as mechanical energy sources. Modern miniature circuit breakers feature an arc chute structure which lengthens, splits and cools the arc before being forced into its bimetallic strip causing expansion unequally before disengaging contacts is loaded apart for disengagement by load out coils allowing it to collapse into its chamber before extinguished by blowout coils allowing it to exit via blowout coils before throwing it back in another separating chamber to finally extinguish it altogether.

This type of breaker has an 11 KV voltage capacity. It features two pairs of contact, with one carrying current while the other made of copper. When opened, one major contact unlocks while the other remains connected, starting an arc when they separate from each other - perfect for switchgear & indoor medium voltage applications.

Types of Breakers

Arc fault circuit interrupters (AFCIs) are being introduced into homes as an electronic way to monitor power grid and detect arc faults that traditional style breakers might miss, such as extreme heat in wiring or potential fire hazards. Residential homes require these breakers for safety.

Molded Circuit Breakers (MCBs) are ideal for higher current applications. Their thermal and magnetic mechanisms can handle up to 2500 amps. If an overload or short circuit occurs, these breakers will immediately trip and prevent fires.

Industrial vacuum circuit breakers are another option for medium voltage applications, featuring a vacuum chamber where abnormal electrical conditions will be directed and where any arc would be directed when abnormalities arise. They're commonly found on appliances rated between medium to high voltage levels and work by blowing out any overload or short circuit with an air blast in case an overload or short circuit occurs.

Other types of breakers include blade breakers, so called for their general appearance. This unit features two protruding "blades" from its housing that are suitable for use with most standard fuse blocks and follow fuse footprint. Also referred to as SF6 circuit breakers due to operating using sulfur hexafluoride gas, they're suitable for use with most standard fuse blocks as well.