Submitted by – Raj Kishore
AIR CIRCUIT BREAKER
MCCB (Moulded Case Circuit Breaker)
A molded case circuit breaker is a plastic that
interrupts an electrical current if the current exceeds
the trip rating of a breaker.
Rated current up to 1000 A
MCCBs provide overload and short-circuit protection
for all applications. The thermal & magnetic
elements, adjustable over a wide band, make these
MCCBs ideal for any distribution application.
Servo controller setting formula
(MCCB Rating X 1.05/C.T) for holding current
(MCCB Rating X 1.3/C.T) for Tripping current
Types of MCCB
Current Rating Breaking Capacity
G-frame 16A - 160A 10KA, 16KA, 25KA
A frame 25A -125A, 160A-200A, 160A-
10KA, 25KA, 31KA
F frame 25A - 250A 35KA, 50KA
C frame 160A-800A 35KA, 50KA
L frame 400A, 250A, 320A, 315A, 630A,
D frame 800A, 1200A, 1000A, 1600A 50KA
THERMAL TESTING –
Thermal testing is done for check breaker is TRIP or Not when overload current is flow. Those current which are
obtained during overload time period.
given overload current is 3In or 2In.
Magnetic testing is done for check breaker is TRIP or Not when short-circuit current is flow.
for Holding Current- 80% of breaker rating X10
for tripping current–120% of breaker rating X10
TRIP/NOT TRIP TEST-
during this test breaker hold in ON position for 2Hr at 105% current of breaker rating and after holding 2Hr
current is given 130% of breaker rating for next 2Hr for checking breaker is Trip or NOT.
MECHANICAL ENDURANCE TEST-
During this test we check working operation of mechanism which are used to CONNECT or DISCONNECT the
moving contact to fixed contact. These TESTING is done by using AIR PRESSURE for moving the mechanism.
During these test operation is done 1 million.
Wide range: 16A to 1600A (AC)
Adjustable thermal setting (70-100%) In.
Adjustable magnetic setting (5-10 times / 4-10 times) In.
Suitable for use as switch disconnector
In 4PwSN version, neutral makes first and breaks last
Push to trip button provision
Uniform front escutcheon plate
Positive dolly position indication
Suitable for DC application up to 1600A
Separate main and arcing contacts
Wide range of accessories
AIR CIRCUIT BREAKER (Rating 630A to 4000A)
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.
Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some
mechanically-stored energy (using something such as springs or compressed air) contained within the breaker is
used to separate the contacts, although some of the energy required may be obtained from the fault current
itself. Small circuit breakers may be manually operated and electric motors to restore energy to the springs
1.Acuator lever - used to manually trip and reset the circuit breaker.
Also indicates the status of the circuit breaker (On or Off/tripped).
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.
A contactor is an electrically controlled switch used for switching a power circuit. contactor range
from 9A – 630A in 3P & 4P execution. The contactors provide reliable and safe switching and the
thermal relays offers close & accurate protection against overload.
TYPES OF CONTACTOR
CN Series: AC contactor with AC coil
CD Series: AC contactor with DC coil
CH Series: AC contactor with AC / DC coil
Latest: Fully application oriented conforming to IS/IEC 60947-4-1
Wide Range: CR, 9A – 95A (4kW – 45kW) in 6 frame sizes
System Design: For a compact system building built in aux. contact 1NO / 1NC up to 32A and 1NO + 1NC from
40A to 95A
Execution: 3P / 4P
Control: AC / DC
Utilization Category: 12 AC Duty Categories,4 DC Duty Categories
Flexible: Common add-on, side & front mounted aux. contact & accessories
Options: Diagonal or same side wiring on coils up to 95A
Indian Conditions: Liberal creepage distance & superior material grade
Safety: Shrouded terminals to prevent accidental contact with live parts
Facility: DIN Rail Mounting up to 95A & direct mounting with O/L relays up to 95A
Modular Design: All accessories snap fitted
Conservation: Low coil consumption
The tests performed are:
Flashing & Continuity Test.
Coil current & Wattage measurement Test.
Pick-up / Drop-off Test.
High Voltage Test.
THERMAL OVERLOAD RELAY
RELAY is sensing device which is used to sense the abnormal condition and break the circuit.
A thermal overload relay is a device to protect an electrical device like a motor/generator from
catching fire/burning out due to excessive heat produced during operation. The relay has a bi-
metallic contact that operates with temperature. When the temperature of the system goes above a
pre-set value, contact goes from closed position to open, and the power supply to the circuit is cut
and the device is saved from damages. So it keeps the system with in the Safe operating
• Auto / manual reset
• Manual reset
Contactor Mounting - 0.1A - 93A in 24 direct reading version (Auto / manual).
Contactor Mounting - 0.1A - 80A in 20 direct reading version (Manual).
Individual Mounting - 0.1A - 93A in 24 direct reading version (Auto / manual & Manual).
Electronic Individual Mounting - 30A - 630A in 8 direct reading version (Manual).
Protection against overload & single phasing
Auto manual / manual reset facility
Ambient temperature compensated
Potential free trip contacts
Test mode facility
Contactor mounting / Individual mounting with
Matching to contactor rating upto 95A
A capacitor is a electrical component used to store energy in an electric field.
An ideal capacitor is characterized by a single constant value, capacitance, measured in FARADS,
practically in MICRO-FARADS (MFD). This is the ratio of electrical charge on conductor to the
potential difference between them.
TYPE OF CAPACITOR
1. MFD- Micro-farads- These are made by the MFD rating for the general purpose.
2. KVAR- These are the power capacitor, which are made for the special purpose of improving the
power factor. These are also called PFC capacitor.
GENERAL USAGE OF CAPACITORS
To block the flow of DC in electronic circuit.
Used in FANS.
Usage as an energy storage device.
For improving the power factor.
load bank is a device that is used in developing an electrical
load which it applies on an electrical power source and converts
the resultant power output. It is used to copy the operational
load which would be used by an actual application that received
its electrical load direct from the power source. Other than serve
the power source, the load bank protects it using its energy
The APFC panel is Automatic Power Factor Correction Panel is used to control the power
factor in a real system, where continuous fluctuation in voltage or current are there. It
contain the bank of capacitor connected in parallel.
The busbar chamber are used to distribute electrical power. The main supply is fed through the incoming
module to a busbar, made of copper wire. And electrical output is taken from the ends of busbar. These
are available for 100A to 800A in 4 way, 6 way and 8 way.
Enclosure are made of special grade CRCA steel are available for housing A,G,C and L FRAME