Types of Electrical Circuit Breakers
Electrical Circuit breakers are the circuit current interrupting mechanism which opens or closes as per the operator command or any fault. Circuit breaker types are classified according to many different criteria such as
- Applicable Voltage
- Location where it is installed
- External design characteristic
- Medium used for the interruption (most popular types)
Circuit breaker types based on voltage
The circuit breakers based on voltage are classified in to groups.
Low voltage circuit breakers:
The breakers which are rated for use at low voltages up to 2kV are called low voltage circuit breakers. These are mostly used in small scale industries.
High Voltage circuit breakers:
The breakers which are rated for use at voltages greater than 2KV are called as high voltage circuit breakers. High voltage circuit breakers are further subdivided in to transmission class breakers which are rated 123KV and above and distribution or medium voltage class (lesser than 72KV) circuit breakers.
Circuit breaker types by installation location:
Based on their location of installation circuit breakers are classified as indoor circuit breakers and outdoor circuit breakers.
Indoor circuit breakers:
These breakers are designed for use only inside buildings or weather resistant enclosures. Generally indoor circuit breakers are operated at medium voltage with a metal cad switchgear enclosure.
Out Door Circuit breakers:
These breakers are designed to use at outside without any roof. So these breakers external enclosure arrangement will be strong compared to indoor breakers to with stand wear and tear.
In conclusion the only difference between indoor and outdoor circuit breakers is the external structural packaging or the enclosures that are used. Besides that all other parts like circuit interrupting mechanisms will be the same for the same operating voltage.
Circuit Breaker types based on External design:
Based on their structural design the circuit breakers are classified as dead tank circuit breakers and live tank circuit breakers.
Dead Tank Circuit breakers:
A breaker which has its enclosed tank at ground potential is called as dead tank circuit breakers. The tank encloses all the interrupting and insulating medium. In simple it can be said that the tank is shorted to ground or it is at dead potential. Dead tank circuit breakers are preferred choice in US.
Advantages of Dead tank breakers over live tank breakers:
- Multiple current transformers can be installed at both, the line side and load side of the breaker.
- This construction offers higher seismic withstand capability because it is almost near to the ground.
- Easy installation and factory made adjustments.
Live tank circuit breakers:
A Breaker which has its tank housing the interrupter is at potential above the ground is called as live tank circuit breaker. As the name specifies it is above the ground with some insulation medium in between.
Advantages of Live tank circuit breakers:
- Cost of the circuit breaker is less
- Less mounting space is required
- Use a lesser amount of interrupting medium.
Circuit breaker type by interrupting mechanism:
This is main class of circuit breaker types. According to the arc interrupting and insulating medium that is used the circuit breakers classified as follows:
Air Circuit breaker:
This uses air as interrupting and insulating medium. These are further classified as Air magnetic circuit breakers and Air blast circuit breakers.
Oil circuit breaker:
This uses oil as interrupting and insulating medium. The oil circuit breakers are divided in two types based on the pressure and amount of oil used as Bulk oil circuit breaker and minimum oil circuit breakers.
These two types are older circuit breakers. In recent years in addition to the above two, two more interrupting mediums are introduced.
Vacuum circuit breakers:
This uses vacuum as the interrupting medium because of its high dielectric and diffusive properties as interrupting medium.
SF6 Circuit breakers:
SF6 has 100 times high dielectric strength than air and oil as interrupting medium. The breaker with SF6 interrupting medium is called as SF6 circuit breaker.
Other types of circuit breakers:
The following are some other types of circuit breakers.
MCB (Miniature circuit breaker):
These current ratings are less than 100A with only one over current protection in built within it. The trip settings are not adjustable in MCB.
MCCB (Moulded case circuit breakers):
These current ratings are higher at 1000A. This has earth fault protection in addition to over current protection. The trip settings of the breaker can vary easily.
Single pole circuit breaker:
It has one hot wire and one neutral wire operated at 120V. on fault it interrupts only one hot wire.
Double pole circuit breaker:
In case of 220 V there are two hot wires, so two poles are needed to interrupt the two hot wires on fault. Double pole circuit breaker is used in this case to interrupt the two hot wires.
GFI or GFCI circuit breaker (Ground fault interrupter):
These are safety switches which trips on ground fault current. In brief this breaker interrupts the electrical circuit when a variance is detected between phase and neutral wires.
Arc Fault circuit interrupter (AFCI):
It interrupts the circuit during excessive arc conditions and prevents fire. Under normal arcing condition this will idle and does not interrupt the circuit.