Miniature Circuit Breaker
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Miniature Circuit Breaker (MCB) types and Ratings

MCB stand for Miniature Circuit Breaker. It is a most important device for electrical circuit. MCB can be different types and different ratings. I am today going to discuss about MCB’s definition, types and available ratings in the market.

What is an Miniature Circuit Breaker (MCB)?

MCB stand for miniature circuit breaker. An MCB is an electromechanical device that switches off an electrical circuit if an over current is detected. The overcurrent in an electrical circuit may result from short circuit, overload or faulty design. There are many types of MCBs are discussed below.

Types of Miniature Circuit Breaker (MCB) According to Number of Pole(s).

According to number of pole(s), there are five types of Miniature Circuit Breaker. Those are SP, DP, TP, TPN and 4P.


SP stands for single pole, those MCB’s have single pole, means one current flowing path are called Single pole (SP) MCB. It is used for controlling single phase electrical load like light, fan etc.


DP stands for duel pole. Those MCB’s have two current flowing paths are called Duel Pole(DP) MCB. DP also used for single phase supply but where need to break phase and neutral both.


TP stands for three poles. This types of MCB have three poles, means three current carrier. TP MCB is used for three phase load like three phase motor.

Photo: SP, DP & TP MCBs

This three types (SP, DP and TP) of MCBs are widely used. Another two types of MCBs are


TPN stands for three pole and neutral. It has three pole which are automatically operated and an isolated pole for neutral.


4 Pole miniature circuit breaker has four poles and all four poles are automatically operated. Three poles for three phases and one for neutral.

Photo: TPN & 4 Pole MCBs

Types of Miniature Circuit Breaker (MCB) Based on Tripping Characteristics

Miniature Circuit Breakers (MCBs) are classified into different types according to tripping over the range of fault current. The widely used MCB types are as Below.

1. Type A MCB

Type A MCBs are highly sensitive devices which trips instantaneously when the current reaches 2 to 3 times the rated current. It’s used for the protection of highly sensitive devices.

2. Type B MCB

This type of MCB trips Between 3 and 5 times of full load current. Type B MCBs are mainly used for domestic applications or light commercial applications where connected loads are primarily lighting fixtures, domestic appliances with mainly resistive elements. It is also used for computers and electronic equipment with very low inrush loads. The surge current levels in such cases are relatively low.

3. Type C MCB

This type of MCB trips between 5 and 10 times of full load current. Type C MCBs are used in commercial and industrial applications where there could be chances of higher values of short circuit currents in the circuit. The connected loads are mainly inductive in nature.

4. Type D MCB

This type of MCB trips between 10 and 20 times of full load current. This type MCBs are used in industrial applications where current inrush can be very high, such as transformers or X-ray machines, large winding motors etc.

5. Type K MCB

This type of MCB trips between 8 and 12 times of full load current. These are suitable for inductive and motor loads with high inrush currents.

6. Type Z MCB

This type of MCB trips between 2 to 3 times of full load current. These type of MCBs are highly sensitive to short circuit and are used for the protection of highly sensitive devices like semiconductor devices.

Available Ratings of MCBs

The available ampere ratings of MCBs are 1A, 2A, 3A, 4A (these are rare used), 6A, 10A, 13A, 20A, 25A, 32A, 40A, 50A, 63A, 100A (these are most used)

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