Types of Miniature Circuit Breakers (MCB’s)
MCBs are classified into three major types according to their instantaneous tripping currents. They are
- Type B MCB
- Type C MCB
- Type D MCB
Type B MCB
This type of MCB will trip instantly at a rate of three to five times its rated current. These are normally used for resistive or small inductive loads where switching surges are very small. Therefore, these are suitable for residential or light commercial installations.
Type C MCB
This type of MCB will trip instantly at a rate of five to ten times its rated current. These are normally used for high inductive loads where switching surges are high such as small motors and florescent lighting. In such cases, type C MCBs are preferred to handle higher value of short circuit currents. Therefore, these are suitable for highly inductive commercial and industrial installations.
Type D MCB
This type of MCB will trip instantly at a rate of ten to twenty five times its rated current. These are normally used for very high inductive loads where high inrush current are very frequent. These are suitable for specific industrial and commercial applications. The common examples of such applications include x-ray machines, UPS systems, industrial welding equipment, large winding motors, etc.
The above three types of MCBs provide protection within one tenth of a sec. The minimum and maximum trip currents of these MCBs are given in a tabular form below, where Ir is the rated current of the MCB. MCBs can also be classified based on number of poles such as single pole, double pole, triple pole and four pole MCBs.