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. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

2. Prepared by;
name en.number
• Vikram rajpurohit 140500116033
• Taxak mistery 140500116016
• Pranay Patel 140500116026
• Parth patel 140500116025
• Paras patel 140500116024
• Akshay rana 140500116034

3. INTRODUCTION
From 19th century use of electricity was started.
Electricity is usefull in domestic & industrial purpose.
Proper precautions should be taken for the safety and
protection of electricity otherwise it may even lead to
death.

4. Elements of electrical engineering
Circuit protection devices
• Fuses
• MCB
• ELCB
• RELAY

5. FuseS
 Fuse Is simplest device,which brakes the circuit
under abnormal condition
 It is used for overload/short circuit protection
in medium voltage (up to 33kV) and low voltage
(up to 400V) installations.

6. CONSTRUCTION OF FUSE
• The main components of a standard fuse unit
consist of the following items:
I. Metal fuse element
II. Set of contacts
III. Support body
IV. Connection

7. Fuses
Glass Cartridge
Mini fuse
Auto fuse
Maxi fuse

8. ADVANTAGES OF FUSES
Speed of operation is very high
Maintenance cost is practically zero
They are capable of clearing high as well as low faults
current
they provide reliable operation

9. DISADVANTAGES
Head produced by the arc may affect the
associated switches
They have to be replaced after each operation

10. MCB
Miniature circuit breaker and moulded case circuit have a
feature of a good h.r.c. fuse and a good switch.
These can be used for switching purpose under normal
operating condition and circuit breaker under
overloading.

11. MCB
All other metal parts are made up of nonferrous ,non-rusting
type materials.
These are used in low voltage domestic, commercials and
industrial application.

12. DIMENSION OF MCB
symmetrical
rail external
part
depth
width

13. Earth leakage circuit breaker (elcb)
the metal housing of the induction of the induction
motor is always connected to earth.
 if the user standing on earth touches the “live” point,
 the protection against such current is essential and it is
provide by device called (elcb)
 operation under the fault condition

14. Earth leakage circuit breaker (elcb)
when the fault occurs , the leakage current start flowing
through conductor as
Explained earlier.
So there will be non zero flux set
up in current transformer core.

15. specification
miniature circuit breaker are available following…
Current ratting : 5,10,15,20,30,40 amp
Voltage rating :a.c. voltage rating – 240v/415
 d.c. voltage ratting – 50v/110
Rupturing capacity : 3ka at 50v

16. Relays
Relays use an electromagnet to operate a switching mechanism
mechanically , but other operating principles are also used.
Relays are used where it is necessary to control a circuit by low
power signal or where several circuits must be controlled by 1
signal.

17. Relays
A type of relay that can handle the high power required to
directly control an electric motor or other loads is called a
contactor.
Solid state relays control power circuits with no moving parts
instead using a semiconductor device to perform switching .

19. CONCLUSION
I have collected some information from my study material and some from
internet.
I have studied about all aspect of “FUSES, MCB, ELCB And RELAY”
And prepared this document as per my best knowledge.
GUIDED BY; Prof. Mustakim Haveliwala