Monday, 12 January 2015

a protective device (circuit breaker)

Hello, how are you in this winter season,
In my previous post I have discussed on different types of switches, today I am going to discuss on a special type of switch as well as a protective device (circuit breaker)
The name of this device is MCB(Miniature circuit breaker)
Why should we use a MCB in a circuit and why nit a normal fuse?
In case of general purpose switch ,if the fuse wire burns out, we need to open the fuse from the panel board and make it again,
But if we use a MCB we don’t need to do this,
We should use a MCB in general for three common purpose 1.short circuit protection 2.overload protection  3. As a hand operated on/off switch
Main parts of a MCB-

1.a bimetallic strip, 2.a trip coil, 3.hand operated switch
How it works- it is interfaced in series with the load, if there is a fault in the load like the load is short-circuited of drawing more current than the rated value of current of MCB, the bimetallic plate gets hotter and bents and make the circuit disconnected, at first current enters through the input terminal then passes through the bi-metalic plate then the trip coil flowing through the moving contact and fixed contact it reaches the output terminal. If more current than the rated value flows through the circuit or in the time of short circuit the trip coil induces such amount of mmf that is enough to heat the latch point making the latch displaced ,
Spark is generated during the movement of moving contact on the fixed contact, to suppress the spark a spark split is placed inside the MCB,
In my next post I will show ,how to interface a MCB in house wiring,
Thank you for reading ,
Good night, have a sweet dream