A circuit breaker is a safety device that automatically interrupts the flow of electrical current in a circuit when it detects a problem, such as an overload or short circuit. This prevents damage to the electrical system and potential fire hazards.
Circuit breaker working is as follows:
- Current Sensing: The circuit breaker has a mechanism that continuously monitors the current flowing through the circuit. This is usually done using an electromagnetic coil or a bimetallic strip.
- Overload Detection: If the current flowing through the circuit exceeds a safe threshold, the circuit breaker’s sensing mechanism is triggered. This could happen due to an overload (too many devices drawing power) or a short circuit.
- Contacts Separate: When the sensing mechanism detects an overcurrent, it triggers a mechanism that physically separates the metal contacts inside the circuit breaker. This interrupts the flow of electricity through the circuit.
- Arc Extinguishing: As the contacts separate, an electric arc is created. The circuit breaker is designed with features to quickly extinguish this arc, preventing it from causing further damage.
- Tripping the Breaker: The act of the contacts separating is what “trips” the circuit breaker, causing the handle or button to flip to the “off” position, indicating the circuit has been interrupted.
- Manual Reset: Once the circuit breaker has tripped, the user must manually reset it by flipping the handle back to the “on” position before power can be restored to the circuit.
The automatic detection and interruption of current flow is what makes circuit breakers an essential safety feature in modern electrical systems.
Following are the types of circuit breakers used in residential and commercial electrical systems:
- Thermal-Magnetic Circuit Breakers:
- These are the most common type of circuit breakers found in homes and small commercial buildings.
- They use a bimetallic strip that bends when heated by excessive current, triggering the circuit breaker to trip.
- They also have a magnetic trip mechanism that senses high short-circuit currents and trips the breaker.
- Electronic Circuit Breakers:
- These use advanced electronic sensors and microprocessors to detect overcurrent conditions.
- They offer more precise and reliable tripping characteristics compared to thermal-magnetic breakers.
- Electronic breakers are often used in more sophisticated commercial and industrial applications.
- GFCI (Ground Fault Circuit Interrupter) Breakers:
- GFCI breakers are designed to protect against ground fault electrical shock hazards.
- They rapidly detect any imbalance in the current flowing in the hot and neutral conductors and trip the circuit.
- GFCI breakers are commonly used in bathrooms, kitchens, laundry rooms, and outdoor locations in homes.
- AFCI (Arc Fault Circuit Interrupter) Breakers:
- AFCI breakers are used to detect electrical arcing conditions that can lead to fires.
- They use advanced electronic sensing to detect the unique signatures of arcing faults.
- AFCI breakers are required in many residential applications to enhance fire safety.
- Combination AFCI/GFCI Breakers:
- These breakers combine the functionality of both AFCI and GFCI breakers into a single device.
- They provide protection against both electric shock and arc fault fire hazards.
- Commonly used in modern residential and light commercial settings.