The document is a lecture on fuses, miniature circuit breakers (MCBs), and earth leakage circuit breakers (ELCBs) by Professor G. B. Rathod. It defines fuses as sacrificial devices that provide overcurrent protection, and describes common fuse types like automotive and high voltage fuses. MCBs are defined as small trip switches that protect electric circuits from overloads, and the types of MCBs like low-voltage, magnetic, and thermal-magnetic are outlined. ELCBs are safety devices that prevent electric shocks, and voltage-operated and current-sensing ELCBs are introduced.

1. Compiled by : Prof. G. B. Rathod
Subject: ES102-ElectronicsWorkshop
EC Department, BVM Engineering College
Email:ghansyam.rathod@bvmengineering.ac.in
Practical No-9:FUSE-MCB-ELCB

2. •Outline
Fuse Definition
Fuse type
MCB Definition
MCB Type
ELCB Definition
ELCB working
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3. Fuse Definition
 A fuse is a type of low resistance resistor that acts as a
sacrificial device to provide overcurrent protection, of either
the load or source circuit.
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4. •Types of fuse
 Automotive fuses
1. Blade type
2. Glass tube or Bosch Type
3. Fusible links
4. Fuse limiters
 High Voltage Fuses
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9. •MCB
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10. •MCB Definition
(Electronics) miniature circuit
breaker; a small trip switch
operated by an overload and used
to protect an electric circuit,
especially a domestic circuit as an
alternative to a fuse.
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11. •Types of MCB
Low-voltage circuit breakers
MCB (Miniature Circuit Breaker)—
rated current not more than 100 A.
Trip characteristics normally not
adjustable. Thermal or thermal-
magnetic operation.
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12. •Two pole MCB
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1. Actuator lever - used to manually trip and
reset the circuit breaker. Also indicates the
status of the circuit breaker (On or
Off/tripped). Most breakers are designed so
they can still trip even if the lever is held or
locked in the "on" position. This is
sometimes referred to as "free trip" or
"positive trip" operation.
2. Actuator mechanism - forces the contacts
together or apart.
3. Contacts - Allow current when touching and
break the current when moved apart.
4. Terminals
5. Bimetallic strip.
6. Calibration screw - allows
the manufacturer to precisely adjust the trip
current of the device after assembly.
7. Solenoid
8. Arc divider/extinguisher

14. •Types Contd..
 Magnetic circuit breakers
Magnetic circuit breakers use a solenoid (electromagnet)
whose pulling force increases with the current. Certain designs
utilize electromagnetic forces in addition to those of the
solenoid.
 Thermal magnetic circuit breakers
Thermal magnetic circuit breakers, which are the type found in
most distribution boards, incorporate both techniques with the
electromagnet responding instantaneously to large surges in
current (short circuits) and the bimetallic strip responding to
less extreme but longer-term over-current conditions.
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15. •Types contd..
 Common trip breakers
When supplying a branch circuit with
more than one live conductor, each live
conductor must be protected by a breaker
pole. To ensure that all live conductors are
interrupted when any pole trips, a
"common trip" breaker must be used.
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16. •Types Contd..
 Medium-voltage circuit breakers
Medium-voltage circuit breakers rated
between 1 and 72 kV may be assembled
into metal-enclosed switchgear line ups for
indoor use, or may be individual
components installed outdoors in
a substation.
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17. •Types contd..
 High-voltage circuit breakers
Electrical power transmission networks are
protected and controlled by high-voltage
breakers. The definition of high voltage varies
but in power transmission work is usually
thought to be 72.5 kV or higher, according to a
recent definition by the International
Electrotechnical Commission (IEC).
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19. •Types contd..
 Sulfur hexafluoride (SF6) high-voltage
circuit breakers
 Hybrid Switchgear Modules
 Disconnecting circuit breaker (DCB)
 Carbon dioxide (CO2) high-voltage
circuit breakers
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20. •ELCB
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 An Earth Leakage Circuit Breaker (ELCB) is a safety
device used in electrical installations with high earth
impedance to prevent shock.

21. •Types of ELCB
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 Voltage-operated
Voltage-operated ELCBs were introduced in the early 20th century, and
provided a major advance in safety for mains electrical supplies with
inadequate earth impedance.
 Current- sensing protection
Residual-current devices (RCD)s protect against earth leakage using a
different method of detection. Both circuit conductors (supply and
return) are run through a sensing coil; any imbalance of the currents
means the magnetic field does not perfectly cancel. The device detects
the imbalance and trips the contact
 Click here to see the working of MCB

22. Thank You
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