What are types of MCB
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What Are The Types Of MCB

What are the types of MCB? There are many types of MCBs based on their tripping characteristics and according to the number of pole(s). Before going to discuss about the types of MCB, let’s know what MCB is.

What is an MCB?

MCB stand for miniature circuit breaker. It is an electromechanical device that switches off the circuit if any abnormality is detected. MCB easily senses the overcurrent caused by short circuit or over load condition.

The miniature circuit breaker has a straightforward working principle. Additionally, it has two contracts; one is fixed and other is movable.

If the current increases, the movable contract is disconnected from fixed contract, making the circuit open and disconnects them from the main supply.

Types of MCB Based on Tripping Characteristics

MCBs are classified into different types according to tripping over the range of fault current. The important types are A, B, C, D, K and Z.

Type A MCB

Type A miniature circuit breaker (MCB) is highly sensitive circuit breaker which trips instantaneously when current reaches 2 to 3 times the rated current.

This type MCB is mainly used for the protection of highly sensitive devices like semiconductor.

Type B MCB

Type B MCB trips when the current reaches 3 to 5 times the rated current with an operating time of 0.04 to 13 Seconds. Type B miniature circuit breaker (MCB) is used for purely resistive loads, such as lighting circuit.

Type C MCB

This type MCBs are widely used in commercial and industrial sector. These are used with inductive loads like motors, fans, transformers etc. Type C MCB trips when current reaches 5 to 10 times than the rated current with an operating time of 0.04 to 5 Seconds.

Type D MCB

Type D MCB trips when the current reaches 10 to 20 times the rated current with an operating time of 0.04 to 3 Seconds. This type MCB is used for highly inductive loads like heavy motors, x-ray, welding machine etc.

Type K MCB

This type miniature circuit breaker trips when the current reaches 8 to 12 times than the rated current with an operating time of less than 0.1 Second. This Type MCB is used for inductive load where have a chance of high inrush current.

Type Z MCB

Type Z MCB is also operates in less than 0.1 Second Like Type K MCB, if the current reaches 2 to 3 times than the rated current.

TypeTripping CurrentOperating Time
A2-3 times than the rated currentInstantaneously
B3-5 times than the rated current0.04-13 Seconds
C5-10 times than the rated current0.04-5 Seconds
D10-20 times than the rated current0.04-3 Seconds
K8-12 times than the rated current<0.1 Second
Z2-3 times than the rated current<0.1 Second
Table: Different Types of MCB

How to know MCB type?

The type of an MCB is usually written just before/with the ampere rating written in the front end of MCB. Look at the picture below, the red arrow and circle are indicating the type of the MCB. It is a Type C MCB with 20 ampere rated current.

TYPE C MCB

C 20A indicates that, the type of the MCB is C and current rating is 20 ampere.

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