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Molded Case Circuit Breakers (MCCB)

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

Molded Case Circuit Breaker (MCCB) is a circuit breaker and trip device assembled in a mould case. The case functions as both an outer wrapper and to retain in proper position the breaker’s internal components. Theses cases are made from various types of electrical insulating and fire retardant plastic. MCCB can automatically cut off electric power in case of overload and short circuit. It is meant for higher rated current and is commonly used in Industrial applications.

 Operation

The basic function of a circuit breaker is to interrupt fault current flowing through it. The circuit breaker mainly consists of fixed and moving contacts. In normal “on” condition of circuit breaker, these two contacts are physically connected to each other due to applied mechanical pressure on the moving contacts.

Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically-stored energy (using something such as springs or compressed air) contained within the breaker is used to separate the contacts, although some of the energy required may be obtained from the fault current itself. Finally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit.

A number of leading companies provide different types of molded case circuit breakers depending on the usage, breaking capacity and cost of the device. L&T provides the DH series, DU series and the Dsine series of MCCBs with varying breaking capacites. While Siemens provides the 3VT series and the 3VL series of MCCB, Schneider has the Easypact, CVS and NSX series of MCCBs. GE has the renowned globally used LM series and the Spectra series of MCCBs.