An Understanding Of The Various Type Of Circuit Breakers & Fuses

What is Circuit Breaker?

It’s a switching device that can be operated automatically or manually in order to respectively protect or control electrical power systems. The existing power systems face influxes or even big electrical currents, which is why the arc produced during the operation time of a circuit breaker should have a safe interruption.


Types of Circuit Breaker

Circuit breakers are divided depending on their arc quenching media –

MCB (Miniature Circuit Breaker)

  • Non-adjustable trip characteristics
  • Rated current at a maximum of 100 A.
  • Thermal-magnetic or thermal or operation

MCCB (Moulded Case Circuit Breaker)

  • Adjustable or non-adjustable trip current
  • Thermal-magnetic or thermal or operation
  • Rated current can go to a maximum of 1000 A.

ACB (Air Circuit Breaker)

  • Often fully adjustable trip characteristics (included configurable trip delays and thresholds)
  • Rated current can go to a maximum of 10,000 A.
  • Almost always controlled electronically
  • Few models are controlled through a microprocessor
  • Mainly used in big industrial plants

RCCB (Residual Current Circuit Breaker)

  • Neutral and Phase (line) connected through RCD.
  • If there is an earth fault current, or a mismatch between two currents flowing through phase and neutral, they trip the circuit within 30 miliseconds
  • The maximum rated current of is chosen according to the maximum load current it is expected to carry
  • Shock Proof

RCBO (Residual Current Breaker with Overcurrent)

RCBO is for those that require an RCD and an MCB in a single unit. It has the same rating as an MCB and is especially beneficial for protection of the people and connected equipments as it immediately senses faults in the currents and trips the entire circuit. Its characteristics include-

  • Breaking capacities of a wide range, ranging from personal use to industrial.
  • Rated currents can go as high as 125 A
  • Sensitivities can go as high as 1000 mA

What is a Fuse?

Moglix Explains, fuses are electronic devices that are put in place in order to protect circuits from current overloads, and over current. How does this happen? The fuse contains a piece of low resistance metallic wire inside a non combustible material that that melts upon coming in contact with excessive current.

Then the power supply is disconnected from the system. An average fuse wire does not in any way interfere with the functioning of the system’s operations, while at the same time manages to remain connected to the power supply till the time it melts.

Types of Fuses

There is a wide variety of fuses which are flooded in the marketing, and their categorization is done on the basis of their use. Here are the 3 most popular categorizations of fuses-

  1. One time use only Fuse and resettable fuses

One time use fuses consist of a wire which immediately melts or burns out upon coming in contact with an overload of electrical current, over current of mismatched load connect. Once the wire melts, the fuse (which is cheap and easily available) has to be replaced manually.

Resettable fuses are devices, which just as the name suggests, can be used (or re-set) many times without worrying about replacing them. These fuses open the circuit when an overload occurs and after a set period of time, they connect back the circuit. PPTC (Polymeric positive temperature coefficient) is an electronic device that used to protect the entire circuit against short current faults.

  1. AC and DC Fuses

There is very little difference between DC and AC Fuses.

For DC fuses that work through a DC system, the Arc is produced after the wire melts. It becomes difficult to get rid of this arc due to the constant value of the DC. The best that can be done is to minimize the fuse arcing and in order to do that, DC fuses are made larger. This is reduces the arc load because of the increased distance between the electrodes.

In AC systems, voltage with a 60 Hertz frequency manages to change the amplitude as high as 60x/sec, which means getting rid of the arc becomes easier. This is why there’s no need to make AC fuses larger in size.

  1. Others

Here is the miscellaneous category of fuses –

Blade Type fuses: They are also called plug-in or spade fuses, and consist of 2 metal caps on a plastic body which can fit easily inside a socket. Their most popular use is in the automobile industry, where they are used for the protection of short circuits.

Cartridge fuses: Their primary function is protecting electrical appliances from high voltage currents and ratings. They are mostly used in industries but they are equally popular sights in home distribution panels. Cartridge fuses can be available up to 600V AC and 600A.

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