MCB
MCB stands for Miniature Circuit Breaker. MCB acts as an automatic switch that opens in the case of excessive current flow through the circuit and once the circuit becomes normal, it can be closed without any manual replacement. MCB is used as a substitute to fuse in most circuits. Due to the many advantages of MCB over the fuse. Also, MCB is more electrically protected than the fuse.
There are two systems for operation of a miniature circuit breaker.
Thermal effect
A bimetallic strip is used for the thermal operation of a miniature circuit breaker. When continuous overcurrent passes from MCB, the bimetallic strip is heated and bends. The mechanical latch will release due to deflection of the bimetallic strip. As this mechanical latch is associated with the operating system, it causes the miniature circuit breaker to open the contacts.
Electromagnetic effect
At the time of the short circuit condition, the current will sudden rise. Which causes the electromechanical movement of the tripping coil linked with the solenoid. Which immediately release of the latch system, resulting in the opening of the circuit breaker contact.
Construction
of MCB
An MCB is fully enclosed in a molded insulating material. It provides mechanically strong and insulated housing. The switching system has a fixed and a moving contact with which the incoming and outgoing wire is attached. Metals or current carrying parts are made of electrolyte copper or a silver alloy based on the rating of the circuit breaker.
An
electric arc is formed due to the separation of contacts in a situation of
overload or short circuit. All modern MCBs have been considered to handle the
arc interruption
process where arc energy extraction and its cooling by metallic arc splitter
plates are provided. These plates are kept in an appropriate position by an
insulating material. Also, the arc runner is provided to force the arc arising
between the main contacts.
