Circuit breakers and fuses work similarly in that they prevent devices plugged into the power system from spoiling. But while a fuse blows when current incoming exceeds supply, circuit breakers disconnect connections mechanically and can be reused post-repair of faults.
The breaker trips and shuts off electricity when four dangerous conditions occur-overloading, short circuit, ground fault, and arc fault. This article will explain how they work.
Used Circuit Breakers switching system
Circuit breakers are used for electrical system switching and protection of devices from power overloads. These electrical switches can be operated remotely by energizing close or trip coil. They can also be opened or closed while electricity is flowing, which is not possible with fuses. They also have the ability to interrupt high-level currents that would damage semiconductor devices and circuit transformers.
The movable and fixed contacts in a circuit breaker are separated by an insulating medium such as air or mineral oil, to prevent contact degradation and metal fatigue due to repeated interruption of current. When a fault is detected in the circuit, the trip coil gets energized, and the pressure mechanism that holds the movable contacts apart releases the energy stored in this mechanism. This energy causes the moving contacts to separate from each other, opening the circuit inside the breaker.
The contacts’ separation creates a highly conductive and ionized plasma called an arc. Depending on the type of used circuit breakers breaker, this arc can be extinguished or quenched by cooling, compressing or replacing the ionized medium. When the arc is extinguished, the contacts will return to their normal position, and current will flow freely in the circuit. A manual or automatic reset will then bring the movable and fixed contacts together, re-establishing the current flow and ending any potential damage from the fault condition.
Molded Breakers tripping system
Molded breakers are a type of circuit breaker that is used in high current applications and come with a variety of trip features to help ensure the safety of equipment. They also provide protection against electromagnetic, electric and thermal effects of short circuits and overloads. These devices have a range of different ratings and are available in both AC and DC types. The molded breakers also include various types of monitors that help to detect overcurrent conditions and initiate the tripping process. These monitors can include current transformers and solid-state circuits. They can also offer a higher degree of flexibility than electromechanical-magnetic and thermal magnetic trip elements.
When a molded breaker trips, it interrupts the flow of current between its two electrical contacts. This creates a small blow-apart force that helps to separate the contacts and extinguish the arc. This feature is necessary because an arc can be dangerous to personnel and equipment. It can also cause the creation of conductive ionized gases and molten or vaporized metals, which could pose additional hazards.
The operating mechanism, or handle, on a molded breaker has a toggle mechanism that includes quick-make/quick-break type contacts that snap open and closed independent of the speed at which the handle is moved. This feature is necessary to prevent the tripping of the breaker by hand-held tools or other unauthorized personnel.
Vacuum Circuit Breakers fixed and movable
Vacuum circuit breakers operate within a vacuum, i.e., at a pressure between 10–7 to 10-5 torr. They have fixed and movable contacts housed in an arc shield and a vacuum interrupter, which is a steel chamber surrounded by ceramic insulators. The movable contact is moved by stainless steel metallic bellows that are designed to seal the vacuum between the moving & stationary current-carrying contacts.
When the contacts separate in vacuum, they ionize the metal vapors in the contact space and generate an arc between them. The arc is quickly extinguished by the fact that the electrons, ions & metallic vapors produced during arcing rapidly condense on the breaker’s contacts, which results in a fast recovery of dielectric strength.
Hence, vacuum circuit breakers have high operating speed & no need for oil to be used as an insulating medium. This makes them suitable for switchgears with high current switching applications & short-circuit currents. They can also be used in applications where there are low-frequency fluctuations & a requirement for long service life.
They can be operated thousands of times and handle dozens of short-circuit currents without losing their function. They can also be switched back and forth between on & off positions numerous times, making them the ideal choice for fault clearing. Moreover, they don’t require any maintenance work. . Different type of circuit breakers air circuit breakers molded circuit breakers and vacuum circuit breakers.
Air Circuit Breakers tripping system
Air circuit breakers use compressed air for arc quenching instead of oil. The air pressure inside the breaker is high enough to make contact with the arc and quench it before the current can cause a fire. These types of breaker are often used in places with higher short-circuit ratings or where frequent switching occurs. They also offer a lower contact resistance than other breaker types.
When too much current is flowing through a wire, the insulation around it can degrade or even melt. This is dangerous because it means the current is no longer confined to the wire. If the wire is still carrying current, it can start a fire that could damage equipment or destroy the entire power system. Circuit breakers prevent this by detecting excessive current and tripping to stop it before the insulation melts or burns.
There are several different kinds of circuit breakers, including plain air circuit breakers, air blast ACBs, and magnetic blowout ACBs. The main difference between these types is the way they operate. Plain ACBs have points of contact that are in the shape of two horns. They can be either single-point or double-point. They have an operating sequence of CO-t1-C-CO and can sustain opening for t1.
Air blast ACBs are used to protect industrial plants and electrical machines from overheating and fire. They are usually used in places with a high risk of fire or explosion and help maintain indoor medium voltage and switch gears. They can also be used for low-voltage applications, but they can’t handle very heavy fault currents or short circuits. Circuit breaker for sale at surplusrecord. Different type of circuit breakers air circuit breakers molded circuit breakers and vacuum circuit breakers
