What Is a Breaker?
A Breaker is a safety device that protects electric circuits by shutting off the power supply in the event of an abnormal current flow.
It automatically shuts off the power supply when a circuit has a ground fault or when a current exceeding the specified value flows.
When a current exceeding the allowable level flows through a cable, the cable itself gradually heats up. If the current continues to flow for a long period of time, the cable sheath and surrounding combustible materials may ignite due to the heat, resulting in a fire or other danger. Also, in the event of a ground fault in the circuit, electricity will flow through the steel frame of the building to combustible materials, posing a high risk of fire.
To prevent such electrical fires and electric shock injuries to people, a breaker is used to shut off the power supply in the event of a ground fault or overcurrent.
A breaker is a circuit breaker. In general, however, a low-voltage device is called a breaker, while a high-voltage or higher protective device is called a circuit breaker.
Vacuum circuit breakers and oil circuit breakers are used for high voltage.
Uses of Breakers
Breakers are indispensable devices in the use of electricity and are widely used in general and industrial applications. In most cases, breakers are installed on the power supply side of equipment that handles electricity.
The following are examples of where breakers are used:
- Inside the distribution board of a house
- Power circuits of submersible pumps for drainage and tap water pumps
- Power circuits of commercial air conditioners
- Main wiring protection circuits inside cubicles
A distribution board for a house is generally used for breakers, which are installed to prevent house fires and electric shocks to residents. Breakers are also used in pumps that handle water. Submersible pumps, for example, throw their motors into the water, so there is a high risk of electrical leakage, and RCDs are generally used.
They are also used in the power circuits of commercial air conditioners used in commercial facilities. Since air conditioners are prone to ground faults due to the accumulation of condensate inside, and since passersby may also touch them, the use of RCDs is recommended.
Principle of Breaker
A breaker consists of wiring terminals, disconnecting device, casing, etc.
1. Wiring Terminal
Wiring terminals are metal fittings used to connect wires to the Breaker. The push-in type, in which a ferrule terminal or the like is inserted, is often used.
2. Pull-Out Device
A pull-out device is a mechanism that interrupts the circuit in the event of an overcurrent, and is available in thermally-actuated and electromagnetic types. The thermodynamic type uses a bimetal to detect overheating due to overcurrent, while the electromagnetic type detects overcurrents by electromagnetic force due to electric current. There are also products that combine both.
3. Casing
A casing is a component that insulates conductive parts from the outside. The casing insulates the circuit breaker from electric shock even if a person touches it, and is generally made of hard plastic or other materials.
Types of Breakers
There are many types of breakers, which can be classified according to their mounting method and short-circuit interrupting capacity.
1. Classification by Mounting Method
Breakers can be mounted either on the front side or on the back side.
Surface type
This method is mainly used for control panels and distribution boards.
Back-surface type
This type is installed and wired on the back side of the metal panel and is sometimes used for cubicles, etc.
2. Classification by Short-Circuit Interrupting Capacity
There are two types of short-circuit interrupting capacity: economic type and general-purpose type, which are selected according to the short-circuit capacity of the upper system.
Economical type
Low cost, but small short-circuit interrupting capacity.
General-purpose type
More expensive than the economical type, but has the advantage of large short-circuit interrupting capacity.
3. Classification by Function
Functions can be classified into two major types: wiring circuit breakers and ground-fault circuit breakers.
Wiring Circuit Breakers
Wiring circuit breakers protect circuits by shutting off electricity when a certain amount of current flows through a circuit. There are two types of overcurrents: short circuits caused by malfunctions and overloads caused by excessive use of electricity.
If an overcurrent condition persists, the cables may overheat, resulting in fire or ignition. Wiring circuit breakers cut off the power supply before a fire or other danger occurs.
Leakage Circuit Breakers
Also called ELB (Earth Leakage Circuit Breaker), an electrical device that interrupts a circuit when it detects a leakage to prevent accidents and disasters. When the insulation performance of electric cables and electrical equipment deteriorates, electric leakage may occur.
In addition, there is a high risk of electric shock if the equipment comes into contact with the outer box of the electrical equipment in a leakage condition, and a high risk of fire if the equipment leaks through the steel frame of a building. RCDs can prevent these hazards.