Miniature Circuit Breakers (MCBs)

• Miniature Circuit Breakers (MCBs) are generally used for low current application
• This a simple circuit breaker that is used to break the circuit in case of over current
• MCBs are most commonly used in protecting equipment like lamps, heaters, air-conditioners, motors and so on
• MCBs work on the principle of thermo-couple action
• When a current higher than the rated current flows through it, the thermocouple is heated up and trips the MCB
• MCBs are specified as for example : 415 V, TPN (Three Pole Neutral), 32A, 10KA(breaking capacity) and C curve
• There are number of types of MCBs viz :
• 1phase,Single pole
• 1phase 2 pole
• 3 phase 3 pole
• 3 phase 4 pole

Miniature Circuit Breaker – Inner view

1.Actuator lever - used to manually trip and reset the circuit breaker.

2.Actuator mechanism - forces the contacts together or apart.

3.Contacts - Allow current when touching and break the current when moved apart.

4.Terminals

5.Bimetallic strip

6.Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.

7.Solenoid

8.Arc divider / extinguisher