1. MCB
Prepared By:-
Nirali Akabari

2. What is MCB?
MCB(Miniature Circuit Breakers)
A MCB is a mechanical switching device which is
capable of making, carrying and breaking
currents under normal circuit conditions and also
making, carrying for a specified time and
automatically breaking currents under specified
abnormal circuit conditions such as those of
short circuit.

3. In short, MCB is a device for overload and
short circuit protection.
It is a manually or 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.

4. Who described it?
An early form of circuit
breaker was described
by Thomas Edison in an
1879 patent
application, although his
commercial power
distribution system used
fuses.

5. What is it’s purpose?
Its purpose is to protect
lighting circuit wiring from
accidental short-circuits
and overloads.

6. What is it’s function?
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.
Circuit breakers are protect an individual
household appliance up to large switchgear
designed to protect high voltage circuits
feeding an entire city.

7. Advantages of MCB
It automatically switches off the electrical
circuit during abnormal condition of the
network means in over load condition as well
as faulty condition.
The fuse does not sense but Miniature
Circuit Breaker does it in more reliable way.
MCB is much more sensitive to over current
than fuse.

8. Disadvantages of MCB
Only one
disadvantage of
MCB over fuse is
that this system is
more costlier than
fuse unit system.

10. Characteristics of MCB
Rated current not more
than 100 A.
Trip characteristics
normally not adjustable.
Thermal or thermal-
magnetic operation.

12. Thank you.