MCB (Miniature Circuit Breaker) - Electrical C & V

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19 March 2020

MCB (Miniature Circuit Breaker)

MCB (Miniature Circuit Breaker)


                                             



A circuit breaker is an automatically operated electrical switch designed to protect the circuit from power due to excess current from an overload or short circuit. Its basic function after detecting the fault is to interrupt the current flow. But unlike the fuse, it operates once and then has to be replaced by a wire to be replaced, but the circuit breaker can be reset to resume normal operation (either manually. Or automatically).


MCB's Internal Structure



                                           
                                                                Fig 1.MCB Internal Structure



This is the internal structure of the MCB. If you ever open the MCB, you will get to know what is in it and what works in its way, if you want to know then you will know by reading the post and I understand its work in this way. It is a case of MCB Trip occurs in three conditions. Or due to our load current, then again due to short circuit and when someone does it manually. But for the first two trips, two different components have been used in MCB. So first we will talk about how MCB will trip when under load.



MCB Over Load protection Working


                                            
                                                                Fig 2 MCB At over load condition


In the figure you can see that bimetallic strip (a temperature-sensitive electrical contact used in some thermostats, consisting of two bands of different metals joined lengthwise. When heated, the metals expand at different rates, causing the strip to bend), when the current As the temperature increases, the temperature of the bimetallic strip increases and the strip becomes bend which leaves it a stuck liver, which can be seen in figure-3.


                                         
                                  Fig 3.when current increase rating then lever release & MCB Off



And the MCB is tripped off and stops the appliance fitted with the MCB. And protects it from overload.


MCB Short Circuit Protection working


                                           
                                                   Fig 4 Coil part (solenoid) for short protection




                                             
                                 Fig 5.when load short then the coil energizes more than the slider move



                                              
                                                 Fig 6 slider move on then the MCB condition On to Off



                                                 
MCB protects against this second short circuit, in which MCB is tripped when any device is faulted. How this happens is because the solenoid coil inside it, when a short circuit occurs, the solenoid coil in the MCB creates a lot of magnetic field and it pushes the plunger inside it and the MCB is tripped.


Types of Miniature Circuit Breakers

As we all know MCB is used at the domestic and industrial level, so it is made in different types, there are mainly five types. The list of which is given below. To know all of these, we will use an example for which we will have the Full Load Current or Rated Current 10 Amp of MCB. Will assume

Type - B

If the full load current of an MCB is 10 amperes and it is a Type-B MCB, then if there is 30 to 50 ampere current flow from inside it then it will be MCB trip.

Type - C

And similarly if TYPE-C has MCB and its full load current is 10 amperes, then it will be trip when 50 to 100 ampere current flows.

Type - D

And similarly if TYPE-D has MCB and its full load current is 10 amperes, it will be trip when 100 to 200 ampere current flows.

Type - K

And similarly if TYPE-K has MCB and its full load current is 10 amperes, then it will be trip when 100 to 150 ampere current flows.

Type - Z

And similarly if TYPE-C has MCB and its full load current is 10 amperes then it will be trip when 20 to 30 ampere current flows.


Benefits of applying MCB


1. MCB is an automatically switched off circuit which automatically switches off due to overload current and short circuit in the circuit. And it works much faster than the fuse.

2. We can run MCB again after being tripped, but if the fuse burns once, then it has to be replaced by a new fuse.

3. If our MCB is repeatedly tripped, then we can use it again but if the fuse is used in its place then it will have to be replaced again and again which takes a lot of time and it costs money again and again.

4. MCB is much safer than fuse.






MORE DETAILS:-
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