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.
|Type||Tripping Current||Operating Time|
|A||2-3 times than the rated current||Instantaneously|
|B||3-5 times than the rated current||0.04-13 Seconds|
|C||5-10 times than the rated current||0.04-5 Seconds|
|D||10-20 times than the rated current||0.04-3 Seconds|
|K||8-12 times than the rated current||<0.1 Second|
|Z||2-3 times than the rated current||<0.1 Second|
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.
C 20A indicates that, the type of the MCB is C and current rating is 20 ampere.