Circuit Breakers: Essential Safety Devices in Electrical Systems
by Yuvi K - December 18, 2023
What are Circuit Breakers?
Circuit breakers are electrical safety devices designed to protect electrical systems, devices, and personnel against damage caused by short circuits, overload, and other dangerous conditions. They are available in a range of sizes and designs, and come in both ac and dc versions. Examples include main panel breakers in a household or commercial power supply, small sub-panel breakers in a house, and fault-sensing vacuum circuit breakers in oil fields. In some cases, they can also be used to monitor the power supply.
Circuit breakers vary in their design and functionality, but they all have the same purpose: to shut off the flow of electricity when a potentially dangerous situation arises. They work by sensing changes in the current, voltage, and/or power passing through a circuit, and then opening the circuit if a preset threshold is exceeded. In addition, they often offer additional protection against overcurrent, shorts, and ground-faults.
How Does a Circuit Breaker Work?
The main function of a circuit breaker is to shut off the flow of electricity before it reaches a dangerous level. It does this by using a bimetallic strip or an array of contact terminals to open the circuit. These contacts open the circuit when the current flowing through it exceeds the rated current of the breaker, and the contacts rapidly dissipate the heat from the excessive current.
When a circuit breaker is triggered, it opens the circuit by physically moving the contacts apart, allowing the current to stop flowing. This helps protect the entire circuit from further damage.
Types of Circuit Breakers
Circuit breakers come in a range of sizes and designs, and use different components and technologies depending on the level of protection required. The most common types of circuit breakers are:
Thermal-Magnetic Breakers
Thermal-magnetic breakers use both a bi-metallic strip and a magnetic field to open the circuit. When an excessive current flows through the breaker, the bi-metallic strip heats up and expands. This increases the gap between the contacts of the breaker, which stops the current. At the same time, the magnetic field generated by the excessive current attracts a plunger that causes the contacts to open.
Miniature Circuit Breakers (MCB)
Miniature Circuit Breakers (MCBs) are designed to protect circuits against electrical shocks. They are usually installed in residential and commercial power supplies and are the most commonly used circuit breakers. MCBs use a thermal mechanism to shut off the circuit in the event of an overload. The thermal mechanism senses an excess temperature increase in the MCB as an indication that an overload has occurred. This causes the contacts to open, shutting off the circuit.
Molded Case Circuit Breakers (MCCB)
Molded Case Circuit Breakers (MCCBs) are designed to provide higher protection than MCBs. They are usually used in industrial and commercial applications, and can protect against overloads, short circuits, and ground faults. MCCBs also have a number of other safety features, such as an arc-flash protection device to dissipate excess energy generated by an arc fault.
Vacuum Circuit Breakers (VCB)
Vacuum Circuit Breakers (VCBs) are designed for use in high-voltage applications, such as oil fields. They feature a vacuum chamber filled with a metal vapor that has excellent electrical conductivity, and which can rapidly dissipate the heat created by a fault. When a fault occurs, the rapid dissipation of heat shuts off the flow of electricity and prevents further damage.
Conclusion
Circuit breakers are essential safety devices in any electrical system, allowing them to be shut off quickly and safely in the event of a dangerous situation. They can help prevent serious damage from occurring to equipment, people, and structures, and provide peace of mind that the power supply is being monitored and protected in case of a fault.
There are a variety of circuit breakers available to suit different applications, from residential MCBs to high-voltage VCBs. No matter the size or design, all circuit breakers serve one purpose: to provide the highest level of protection for electrical systems, personnel, and property.
