What's MCB? what are the class available in market

What's MCB? |  MCB trip curves B,C,D,K&Z

Class C 32A MCB

Miniature circuit breaker(MCB) is a device automatically or manually breaks an electrical circuit in an abnormal condition like a short circuit or overload condition.

An MCB is used for load break, isolation, and protection of sub-circuit, including motor subcircuit.
MCB available in the standard current ratings of 6,10,16,20,25,32,40,50,63,8,100 and 125A.They are available in domestic and industrual type. the rated short circuit capacity of MCB's are 6,10,15 and 25kA.
MCB's can typically perform 20000  mechanical operations and 2000 or 10000 electrical operations.

Tripping Curve(B, C, D, Z & K).

The graphical plot between In V/s t explains the tripping characteristics of the breaker. Normally five different types of tripping curves MCB's are available in the market.   

MCB Tripping curve OR Class Curve.

Tripping Curve-B:-

The MCB tripping curve B suitable for cable protection with a light load. The MCB will trip instantaneously when the current reaches 4-time's With +/- 20% tolerance of rated current. 

Tripping Curve-C:-

The MCB tripping curve c suitable for domestic application with medium starting current. The MCB will trip instantaneously when the current reaches 8-times With +/- 20% tolerance of rated current.

Tripping Curve-D:-

The MCB tripping curve D suitable for inductive load/motor load with the high starting current. The MCB will trip instantaneously when the current reaches 12-times With +/- 20% tolerance of rated current.

MCB Tripping Curve/ Class Curve.

Tripping Curve-Z:-

Curve Z MCB is very highly sensitive for short circuits and is used to protect the sensitive devices. The Class Z MCB will trip instantaneously when the current reaches 3-times With +/- 20% tolerance of rated current.

Tripping Curve-K:-

The MCB tripping curve D suitable for inductive load with high inrush current. the class K MCB will trip instantaneously when the current reaches 12-times With +/- 20% tolerance of rated current.

The class B and class C MCB's are most commonly used for residential purposes.  Class C MCB can found in Main DB in the residential or commercial buildings and Class B can found in sub-DB. Class Z MCB's used to protect semiconductor device like PLC.