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Electrical circuit breakers - Basic, Operation, and Types

April 19, 2023


An electrical circuit breaker is an automatic switch that protects from damage caused by overloading, short circuit, or other electrical faults and can be found in homes, business and industrial facilities.

Breaker Design: Basic


The simplest circuit protection device is the fuse. A fuse is just a thin wire, enclosed in a casing, that plugs into the circuit. When a circuit is closed, all charge flows through the fuse wire — the fuse experiences the same current as any other point along the circuit. The fuse is designed to disintegrate when it heats up above a certain level — if the current climbs too high, it burns up the wire. Destroying the fuse opens the circuit before the excess current can damage the building wiring.


The problem with fuses is they only work once. Every time you blow a fuse, you have to replace it with a new one. A circuit breaker does the same thing as a fuse — it opens a circuit as soon as current climbs to unsafe levels — but you can use it over and over again.


The circuit breaker is a fundamental device in today's world and one of the most significant safety measures in homes. Whenever the electrical wiring in a building experience an overcurrent, these simple machines halt the power supply until someone can rectify the problem. Without circuit breakers (or fuses), household electricity usage would be unfeasible due to the potential for fires and other chaos that could arise from minor wiring problems and equipment malfunctions.

A circuit breaker consists of three basic parts:

Operating mechanism:  Open and close the contacts of the breaker.


Contacts: Made of conductive materials and are held together by a spring, The contacts are responsible for carrying the current of the electrical circuit. The hot wire in the circuit connects to the two ends of the switch. When the switch is flipped to the on position, electricity can flow from the bottom terminal, through the electromagnet, up to the moving contact, across to the stationary contact and out to the upper terminal.


Tripping mechanism: Responsible for detecting electrical faults and tripping the breaker to interrupt the current flow.

parts of a circuit breaker

How circuit breaker works?    

  1.  When current flows through a circuit, it passes through the contacts of the circuit breaker.

  2.  When the current exceeds the rated limit, the electromagnet inside the circuit breaker is activated, which pulls down a metal lever that is connected to the contacts.

  3.  This causes the contacts to separate, breaking the circuit and stopping the flow of current.

  4.  Once the circuit is broken, the spring causes the contacts to return to their original position, allowing the circuit to be reconnected.

Classify the different types of circuit breaker

High Voltage Circuit Breakers: These circuit breakers are designed to handle voltage levels above 1000 volts. They are commonly used in power transmission systems to protect against overloads and short circuits.

Medium Voltage Circuit Breakers: These circuit breakers are designed to handle voltage levels between 1000 and 72 volts. They are commonly used in power distribution systems, such as in factories, buildings, and substations.

Low Voltage Circuit Breakers: These circuit breakers are designed to handle voltage levels below 1000 volts. They are commonly used in residential, commercial, and industrial applications, such as in homes, offices, and small factories.





Low Voltage Circuit Breakers

Miniature Circuit Breakers (MCBs)

small and compact

protect against damage to electrical devices

Trip-free mechanism

Residential buildings

Commercial buildings

Renewable energy systems


Molded Case Circuit Breakers (MCCBs)

Higher current ratings, up to a few thousand amps

Long lifespan


heavy industries

Air Circuit Breakers (ACBs)

Adjustable trip settings

overcurrent protection


offshore industries

Residual Current Circuit Breakers (RCCBs)

Sensitive protection against electrical shock and fires

Detects ground faults and other current imbalances


commercial industries

Ground Fault Circuit Interrupters (GFCIs)

Provides protection against electrical shock

Senses leakage currents to ground



outdoor outlets

Medium Voltage Circuit Breakers

Vacuum Circuit Breaker (VCB)

High interrupting capacity

Quick operation

Environmentally friendly

Transportation systems

Power generation

SF6 Circuit Breaker

High dielectric strength

Self-healing property

high power equipment


High Voltage Circuit Breakers

Oil circuit breakers

Efficient arc quenching

Can be refilled


electric vehicles