MCBs are classified into different types based on its tripping characteristics that are the range of tripping fault current at which the device operates in the event of short circuit or overload.
Type A Miniature Circuit Breakers
Type A MCBs are highly sensitive devices which trip instantaneously when the current reaches 2 to 3 times the rated current.
Mainly used for the protection of highly sensitive devices.
Type B Miniature Circuit Breakers
A type B MCB trips when the current is 3 to 5 times the rated current with an operating time of 0.04 to 13 Seconds. It is used for purely resistive loads that are non-inductive loads or with a very small inductive load which has no considerable amount of inductance.
These types are mainly used for low power domestic applications like lighting circuits, home wirings, etc.
Type C Miniature Circuit Breakers
Type C operates for a current value of 5 to 10 times than the rated current with an operating time of 0.04 to 5 Seconds. These are used with inductive loads like motors, fans, transformers, etc. where have a chance of sudden current rush or surges.
Mainly used in commercial and industrial applications.
Type D Miniature Circuit Breakers
Type D has a trip current of 10 to 20 times than the rated current with an operating time of 0.04 to 3 Seconds. It is used for very high inductive loads.
Mainly used in high power industrial applications for types of equipment like heavy motors, transformers, x-rays, welding, etc.
Type K Miniature Circuit Breakers
Type K trip when the current reaches 8 to 12 times than the rated current with an operating time of less than 0.1 Second. These are used for inductive loads which have a chance of high inrush currents.
Type Z Miniature Circuit Breakers
Type Z MCBs operates for a current value between 2 to 3 times the rated current with an operating time of less than 0.1 Second.
Type A, K and Z MCBs have extremely small operating time compared to type B, C, and D MCBs. Class A, K, and Z are highly sensitive breakers which operate very quickly in a short time used to protect sensitive devices.
Source: The Mechatrofice