Working of MCCB: ( Molded Case Circuit Breaker)
* The operating mechanism consisting of lever, spring, contacts etc. is used to open or close the MCCB electrically.
* The arc extinguisher facilitates for the quenching of arc by lengthening it which is produced when MCCB gets opened and current is interrupted.
* The trip unit is the brain of the circuit breaker. It senses the overload or shortcircuit condition and trip mechanism is operated to trip the MCCB.
* When overload occurs, the thermal relay mechanism permits overload for short duration, then bimetal strip actuates the tripping mechanism to open the MCCB contacts.
* When short-circuit occurs, large magnetic force produced by short-circuit current operates the lever to trip the MCCB immediately and open the contacts.