This document is a report on an internship at ABB in Nashik submitted by Amol Nanaji Bagul. It includes an acknowledgements section thanking those who helped with the internship. The document then covers topics related to vacuum circuit breakers and vacuum contactors, including their construction, operating principles, testing procedures, and applications. Sections describe key components like vacuum interrupters, operating mechanisms, and control circuits. Maintenance and servicing are also discussed.

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Department of Electrical Engineering
College of Engineering, Pune
INTERNSHIP IN ABB, NASHIK
Report Submitted by
Name : AMOL NANAJI BAGUL
Enrollment Number : 20903007
MIS Number :110905002
Dates of Submission : 02-07-2012

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ACKNOWLEDGEMENT
With all respect and gratitude, I would like to thank all people
who have helped me directly or indirectly for this internship.
I express my heartily gratitude towards Mr. Manoj Wagh sir,
Mr. Devesh sir, Mr. Bharat sir, Mr. Nikhil sir, Mr. Satish, Mr.
Bhupal, Mr. Jayesh and entire staff of ABB, Nashik.
I am ending this acknowledgement with deep indebtedness of
my friends who have helped me complete manuscript.
Amol Bagul
MIS number : 110905002

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INDEX
Vacuum Circuit Breaker
1. Introduction 6
2. Parts of vacuum circuit breaker 6
i. Vacuum Interrupter 6
ii. Primary Disconnects 7
iii. Control Circuit 7
a. Auxiliary Switch 7
b. Motor limit Switch 8
c. Motor Relay 8
d. Anti-pumping Relay 8
iv. Latch check Switch 8
v. Closing Spring Interlock 8
3. Electrical Characteristics 9
4. Quenching Principle of Vacuum Circuit Breaker 9
5. Operating Mechanism of Circuit breaker 10
6. Testing of Vacuum Circuit Breaker 10
i. Visual Inspection 10
ii. Continuity 10
iii. Testing of Breaker 10
iv. Rack in / Rack out 11
v. Contact resistance 11
7. Maintenance of Circuit breaker 11
i. Electrical Endurance 11

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ii. Mechanical Endurance 12
iii. Poles and their Replacements 12
8. Servicing 12
9. Advantages of Vacuum Circuit Breaker 13
10. Applications 13
Vacuum Contactor
1. Introduction 14
2. Construction 15
i. Contacts 15
ii. Fuses 15
iii. Control Circuit 15
3. Operating Principle 16
4. Interruption Principle 16
5. Testing of Vacuum Contactor 17
6. Main Technical Characteristics 18
FIGURE INDEX
1. Vacuum Bottles 6
2. Auxiliary switch 6
3. Anti-pump Relay 7
4. Racking Position 10
5. Control Circuit 15
6. Schematic Diagram of Vacuum Interrupter 16

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VACUUM CIRCUIT BREAKER
1.INTRODUCTION
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, by interrupting continuity, to
immediately discontinue electrical 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.

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2. PARTS OF VACUUM CIRCUIT
BREAKER
a. Vacuum Interrupters: Vacuum interrupters mounted vertically within the
circuit breaker frame, perform the circuit breaker interruption. Consisting of
a pair of butt contacts, one movable and one fixed, interrupters require only
a short contact gap for circuit interruption. The resulting high-speed
operation allows the entire operating sequence, from fault to clear, to be
consistently performed in three cycles or less.
Fig.1.Vacuum bottles
b. Primary Disconnects : The primary connection to the associated switchgear
is through the six primary disconnects mounted horizontally at the rear of
the circuit breaker. They are usually made up of Copper. Do not subject the
primary disconnects to rough treatment. Never use the primary
disconnects as handles when maneuvering the breaker.
c. Control Circuit : The following paragraphs discuss operation of the control
circuit components. The control circuit design may vary, depending upon
customer requirements.
i. Auxiliary Switch : This contact takes initial force from the drive
shaft of breaker, so changes its position with open/close operations of
breaker. If not specified, the default components are 6 normal open

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(NO) and normal close (NC) contacts. These are used in the
open/close control circuit of breaker.
Fig.2.Auxiliary Switch
ii. Motor Limit Switch : The motor limit switch energizes the motor
relay when a drive spring charging operation is required. The motor
limit switch de-energizes the motor relay when the drive springs reach
the fully charged position.
iii. Motor Relay : When energized by the closing of the motor limit
switch, the motor relay energizes the spring charging motor through a
pair of normally open contacts. The motor relay disables the closing
coil through a pair of normally closed contacts.
iv. Anti-Pump Relay : The anti-pumping device prevents close
operation if electrical commands of open and close appear at the same
time. By doing so, possibility of breaker failure is reduced. The
control circuit have an anti-pumping release.
Fig.3.Anti-pump Relay

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d. Latch Check Switch : The latch check switch allows the circuit breaker to
be used for Instantaneous reclosing. The contacts of the latch check switch
connect in series with the closing coil. When the guide cam moves out of its
normal position, it activates the latch check switch. The closing circuit
cannot be energized until the guide cam fully returns to its normal position
and the mechanism is in position to allow a close operation.
e. Closing Spring Interlock : An interlock located between the manual trip
and close lever at the bottom of the circuit breaker prevents the closing
springs from “dumping” when the circuit breaker is closed. An interlock bar
slides under the closing lever after the circuit breaker closes and prevents the
closing lever from being pushed down

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3. ELECTRICAL CHARACTERISTICS

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4. QUENCHING PRINCIPLE OF
VACUUM CIRCUIT BREAKER
Vacuum circuit-breakers does not require an interrupting or insulation medium. In
fact, the interrupters do not contain ionizable material. During the separation of
current-carrying contacts, contact pressure reduces, real contact surface reduces
and the temperature of contacts increases to melting temperature. This produces
metal vapours which initiates and supports the vacuum arc, maintaining until the
next current zero. Due to the special geometry of the spiral contacts, the arc
column is kept rotating by the radial magnetic field produced in order to involve a
wider surface than that of a fixed contracted arc. Thus, overheating and erosion of
the contacts are prevented. So the lifespan of circuit breaker is increased. Since
there is no interrupting or insulation material in the medium, there is no
decomposition gases or particles.

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5. OPERATING MECHANISM OF
CIRCUIT BREAKER
The operating mechanism of the stored energy spring type and acts on the three
poles of the breaker. The necessary operating energy is stored ready for activation
by charging the spring mechanism. The stored spring energy mechanism
essentially consists of drum containing the spiral spring, the charging system, the
latching and the linkages which transmit the force to the breaker poles.

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6. TESTINGS OF VACUUM CIRCUIT
BREAKER
1. Visual Inspection
-Check for all the tightness and all the contacts.
-Check for all colorings.
-Check the all connections as per the drawing.
2. Continuity
-Check for all the wiring as per the drawing.
-This test will show us any the discontinuous connections in that case
continuity fails.
-Do not take continuity test while giving supply to the breaker.
3. Testing of breaker
-In this test breaker is checked electrically and mechanically.
-Do the connections as per the drawing and give the appropriate supply to
motor and coil.
-Take the operations of close and trip electrically
-For mechanical checking charge the breaker mechanically and test using
mechanical on and off button.
4. Rack in and Rack out
Fig.4.Racking Position
-This is used for moving breaker in to the panel or taking out of the panel.

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-When breaker is on and anyone tries to take out the breaker, it does not
come out due to this mechanism.
-Also when breaker is taken out for servicing and anyone tries to on the
breaker, it does not start.
5. Contact resistance :
-This test is for measuring the resistance offered by all the contacts, nuts and
bolts while tightening.
-This should not be greater than specified limit which results in losses.

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7. MAINTENANCE OF CIRCUIT
BREAKER
a. ELECTRICAL ENDURANCE:
The low arc energy provides very high electrical endurance. Besides, the
mechanical lifespan of breaker, instead of how many times the current is chopped,
is the characteristic that determines the lifetime of VCB. The vacuum interrupters
used in EVK type breakers can interrupt “Rated Nominal Current” for about 10000
times and can interrupt “Rated Short Circuit Current” for 100 times.
b. MECHANICAL ENDURANCE:
In regard to the researches committed, 75 percent of the circuit breaker faults is
caused from mechanical inadequacy of breaker. Thus, mechanical endurance is
very important criteria. Vacuum circuit breakers have more advantages than other
types of breakers. VCBs involve fewer mechanical components and require less
force for open/close operations. This leads to the fact that breakers is subject to less
impact, less vibration and thus, less deformation and corrosion.
c. POLES AND THEIR REPLACEMENTS :
For this type of circuit breaker the pole terminals has been placed in epoxy resin
and withdrawable connections are round bar with necessary tubular cover on it.
The breaker pole with vacuum interrupter is maintenance free up to reaching the
permissible number of vacuum interrupter operating cycles.

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8. SERVICING
1. Servicing of the operating mechanism should be performed after 5000
operations.
For servicing the operating mechanism after switching off and taking out
device.
a. Clean the surface in general.
b. Relubricate pauls, support shaft, sliding and rotating bearing surfaces
c. Check the condition of fasteners, pins, bolts and tightness of fastening
screws.
d. Check the condition of the operating mechanism spring.
e. Perform mechanical and electrical function tests.
2. For servicing the poles of circuit breaker.
a. Clean the insulating material surfaces and conductive components.
b. Check the condition of the poles, their parts and ohmic resistance of
poles
c. For testing vacuum without dismantling use vacuum tester to check
vacuum pressure of the bottels.
d. Check if the sum current limit is reached for replacing the poles.

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9. ADVANTAGES OF VACUUM
CIRCUIT BREAKERS
• Very long lifetime of the contacts (This provides longer breaker life.)
• Less maintenance required
• Less moving parts in mechanism
• Less force needed to separate the contacts (since the distance between them is
shorter.)
• Environment friendly. Since interruption takes place in vacuum medium, VCBs
do not require gas or liquid addition. This reduces the possibility of leakage of gas
(or any material) that can be harmful for environment.
10. APPLICATIONS
 Short circuit currents.
 Overhead lines under load and no load conditions.
 Cables under load and no load conditions.
 Transformers under load and no load conditions.
 Generators under load and no load conditions.
 Ripple control system.
 Motors with starting currents above 600 A.

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VACUUM CONTACTOR
1.INTRODUCTION
A contactor is an electrically controlled switch used for switching a power circuit,
similar to a relay except with higher current ratings.[1] A contactor is controlled by
a circuit which has a much lower power level than the switched circuit. Contactors
come in many forms with varying capacities and features. Unlike a circuit breaker,
a contactor is not intended to interrupt a short circuit current. Contactors range
from those having a breaking current of several amperes to thousands of amperes
and 24 V DC to many kilovolts. The physical size of contactors ranges from a
device small enough to pick up with one hand, to large devices approximately a
meter (yard) on a side.Contactors are used to control electric motors, lighting,
heating, capacitor banks, and other electrical loads
All the contactors are available, on request, in one of the two following
versions.
 Single Command Operated(SCO):
closing takes place by supplying auxiliary power to the special input of the
multivoltage feeder. On the other hand, opening takes place when the
auxiliary power is either voluntarily cut off (by means of a command) or
involuntarily (due to lack of auxiliary power in the installation).
 Double Command Operated(DCO):
closing takes place by supplying the input of the closing command of the
apparatus in an impulsive way. On the other hand, opening takes place when
the input of the opening command of the contactor is supplied in an
impulsive way.

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2.CONSTRUCTION
 Contacts :
A contactor has three components. The contacts are the current carrying part
of the contactor. This includes power contacts, auxiliary contacts, and
contact springs. The electromagnet (or "coil") provides the driving force to
close the contacts. The enclosure is a frame housing the contact and the
electromagnet. Enclosures are made of insulating materials like Bakelite,
Nylon 6, and thermosetting plastics to protect and insulate the contacts and
to provide some measure of protection against personnel touching the
contacts. Open-frame contactors may have a further enclosure to protect
against dust, oil, explosion hazards and weather. A basic contactor will have
a coil input (which may be driven by either an AC or DC supply depending
on the contactor design). The coil may be energized at the same voltage as
the motor, or may be separately controlled with a lower coil voltage better
suited to control by programmable controllers and lower-voltage pilot
devices. Certain contactors have series coils connected in the motor circuit;
these are used, for example, for automatic acceleration control, where the
next stage of resistance is not cut out until the motor current has dropped.
 Fuse :
Fuses are connected in series with connection bars for protection of
overcurrent. Note that these are not for the protection of the system but it is
for the protection of the contactor in order to isolate the motor from main
supply.
 Control Module : Control Module is circuitry made on PCB using
electronic components which controls the contactor electrically. Control
Module is shown in figure and is very sensitive to electric supply. In case
Overvoltage it will get damage and contactor will not operate.

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Fig.5.Control Circuit

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3. OPERATING PRINCIPLE
When current passes through the electromagnet, a magnetic field is produced,
which attracts the moving core of the contactor. The electromagnet coil draws
more current initially, until its inductance increases when the metal core enters the
coil. The moving contact is propelled by the moving core; the force developed by
the electromagnet holds the moving and fixed contacts together. When the
contactor coil is de-energized, gravity or a spring returns the electromagnet core to
its initial position and opens the contacts.
For contactors energized with alternating current, a small part of the core is
surrounded with a shading coil, which slightly delays the magnetic flux in the core.
The effect is to average out the alternating pull of the magnetic field and so prevent
the core from buzzing at twice line frequency.

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4. INTERRUPTION PRINCIPLE
The main contacts operate inside the vacuum interrupters (the level of vacuum is
extremely high: 13 x 10-5 Pa). On opening, there is rapid separation of the fixed
and moving contacts in each contactor interrupter. Overheating of the contacts,
generated at the moment they separate, causes formation of metallic vapours which
allow the electric arc to be sustained up to the first passage through zero current.
On passage of zero current, cooling of the metallic vapours allows recovery of high
dielectric resistance able to withstand high values of the return voltage. For motor
switching, the value of the chopped current is less than 0.5 A with extremely
limited overvoltages.
Fig.6.Schematic diagram of vacuum interrupter.

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5. TESTINGS OF VACUUM
CONTACTOR
1. Visual Inspection
-Check for all the tightness and all the contacts.
-Check for all colorings.
-Check the all connections as per the drawing.
2. Continuity
-Check for all the wiring as per the drawing.
-This test will show us any the discontinuous connections in that case
continuity fails.
-Do not take continuity test while giving supply to the contactor.
3. Testing of contactor
-In this test contactor is checked electrically.
-Do the connections as per the drawing and give the appropriate supply to
motor and coil.
-Take the operations of close and open electrically
4. Contact resistance :
-This test is for measuring the resistance offered by all the contacts, nuts and
bolts while tightening.
-This should not be greater than specified limit which results in losses.

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6.MAIN TECHNICAL
CHARACTERISTICS
• Maintenance-free
• Suitable for installation in prefabricated substations and
switchgear both of the card (slim line) and traditional type
• High number of operations
• Direct checking of contact wear
• Long electrical and mechanical life
• Remote control
• Multi-voltage feeder
• Bistable drive of the type with permanent magnets.