The document provides information on different types of motor starters and circuit breakers. It discusses direct online starters, auto transformer starters, and variable frequency drives as types of motor starters. It also describes the key components and classifications of various circuit breakers, including molded case, insulated case, low voltage power, medium voltage air magnetic, and medium voltage vacuum circuit breakers. The classifications are based on voltage class and arc extinguishing methods like air, vacuum, and gas. Key components discussed include the frame, contacts, arc extinguishers, and operating mechanisms.

1. Training on Electrical Starter & Switch Gear

2. Motor Basics

3. Motor Basics

4. Motor Basics

5. Motor Basics

6. Motor Starter

7. Motor Starter

8. Motor Starter
Types of Starters:
1. D.O.L - Direct online Starter
In D.O.L starter full line voltage applied during starting
hence more starting current. Use of D.O.L starter limited to 5 to 10HP and
depends upon rating of Distribution Transformer and base load of MCC
panel. Basic arrangement of D.O.L starter is given below.

9. Motor Starter

10. Motor Starter
Types of Starters:
3. Auto Transformer Starter
In Auto Transformer Starter has following steps.
1. Motor windings are feeding with certain % of line
voltage ( Normally 60,70,80%) through Auto Transformer contactor.
2. After duration of 10 to15 seconds auto-transformer
star contactor de-energized and line contactor switched ON.
3. After 5 seconds of above operation, Auto Transformer
contactor de-energized and line contactor alone switched ON condition.

11. Motor Starter
Types of Starters:
4. Variable Frequency Drive
A Variable Frequency Drive (VFD) is a type of motor
controller that drives an electric motor by varying the frequency and
voltage supplied to the electric motor. Other names for a VFD are variable
speed drive, adjustable frequency drive, AC drive, micro drive, and
inverter

12. Basics of Circuit Breakers
Circuit breakers are used in nearly all electrical systems — from residential buildings to electric utility
facilities. We rely on them to protect our systems from damaging overcurrent and short circuits.
Understanding circuit breaker construction and operation is key to realizing their limitations and proper
usage. This article covers basic components and operation of popular types of circuit breakers, including
molded-case (MCCB), insulated-case (ICCB), low-voltage power (LVPCB), medium-voltage air-magnetic
(MVACB), and medium-voltage vacuum (MVVCB) circuit breakers.
Circuit Breakers Key Components
MCCBs contain five components — a frame, operating mechanism, interrupting structure, trip unit, and
terminal connections. These components are given below
1. Frame — houses and supports the components and also provides insulation to contain the arc.
2. Operating Mechanism — opens and closes the contacts.
3. Interrupting Structure — includes the arc chutes and all current-carrying parts except the trip unit. Arc
chutes are designed to interrupt the arc quickly, usually 1.5 to two cycles for MCCBs and ICCBs.
4. Trip Unit — senses abnormal current flow and causes the operating mechanism to open the contacts.
MCCB trip units are usually of the thermal-magnetic type.
5. Terminal Connections — provides a suitable connection from the breaker to the conductor. Molded-case
circuit breakers typically bolt directly to the bus.
Most manufacturers’ MCCBs have similar components and similar appearance.
ICCBs have the same basic construction as MCCBs, but use solid-state and digital trip units (as opposed
to thermal-magnetic trip units) and have much higher interrupting ratings. ICCBs are often draw-out type,
as opposed to bolt-in, although they can be either.

13. Classification of Circuit Breakers
Circuit Breakers are classified or referred to by their voltage size and arc extinguishing method.
1 Voltage Class:
Circuit breakers are grouped by voltage classes that are normally defined as LOW, MEDIUM, and HIGH.
You will find some texts refer to only two classes, Low Voltage and High Voltage, but the breaker industry
generally use three voltage size groupings.
• Low Voltage (0-600V):
Generally includes Molded Case breakers , Power Metal clad breakers and
the new design large molded frame power breakers
• Medium Voltage (600V through 15KV):
This includes 4160V, 6.9KV and 13.8KV. Sometimes 34KV breakers are
included.
• High Voltage (Above 15KV):
These are usually breakers associated with transmission and first line step
down coming off transmission. Also anything above 34KV is generally outdoor gear.
2 Arc Extinguishing:
All circuit breakers have contacts, and when the contacts separate during an opening operation they draw
an arc, assuming that power is flowing through the device. The electric arc forms between the contacts
and is drawn out in length as the contacts open. Therefore, circuit breakers require a device to control or
remove the arc; the 4 common mediums used to extinguish an arc
during breaker contact separation are Oil, Air, Gas, and opening in a Vacuum.

14. Classification of Circuit Breakers
• Air Circuit Breaker (ACB):
ACB contacts open in air and use a combination of the characteristic of the
arc, air and a magnetic field to extinguish the arc.
• Air Blast Circuit Breaker:
Generally these breakers are used in high voltage applications. They also are
used in high voltage DC applications. As the name implies, the contacts of an air blast breaker separate
in air. Whereas the medium voltage ACB’s have a mechanical device which displaces air into the arc
during opening operation, the air blast breaker use a stream of compressed air directed toward the
separable contacts of the breaker to interrupt
the arc formed when the breaker is opened.
• Vacuum Circuit breakers:
The vacuum circuit breaker interrupts the current in a vacuum. The contacts
of a vacuum breaker are enclosed in a ceramic envelope or "bottle” that is evacuated to an extremely low
atmospheric pressure, approximately .0023 in. Hg
absolute. Although the physics of interruption are quite complex, the vacuum interrupter works because
the arc requires a conducting path to sustain it, but within the vacuum bottle there are no gasses to
ionize; therefore, for all practical purposes, there can be no conducting path and the arc cannot be
sustained.

15. Classification of Circuit Breakers
LVPCBs (Photo given below) are also known as air-frame and draw-out circuit breakers. There are five
major assemblies on a typical LVPCB:
1. Disconnects or Stabs
I) Main disconnects — connect the circuit breaker to the main bus.
Ii) Secondary disconnects — connect the circuit breaker to the control circuits.
Iii) Ground disconnect — connects the circuit breaker to the ground bus.
2. Contacts
I) Arcing — transfers the arc to the arc runners in the arc chute.
Ii) Main — carry the main load current.
Iii) Auxiliary — make and break the control circuits.
3. Arc Extinguishers or Arc Chutes — interrupt and contain the arc.
4. Operating Mechanism — opens and closes the contacts.
5. Overcurrent Trip Device — modern circuit breakers have digital trip units, although older units could be air
dashpot or oil dashpot types. Typical functions are long-time delay (LTD), short-time delay (STD),
instantaneous (INST), and ground fault (GF).

16. Classification of Circuit Breakers
Main Disconnects (stabs)
The main disconnects connect the circuit breaker to the bus. LVPCBs typically use either vertical or
horizontal rows of straight, spring-loaded fingers to make contact with the bus bar, although on larger frame
sizes they may have round or “tulip-style” disconnects. Photo shows the backboard assembly of an LVPCB
with primary, secondary, and ground disconnects clearly visible.
Most medium-voltage metal-clad circuit breakers will use “tulip-style” disconnects and have some type of
spring around them to ensure good contact with the bus. Medium-voltage, draw-out circuit breakers have the
primary disconnects in the switchgear guarded by a shutter mechanism installed in the switchgear cubicle.
As the circuit breaker is removed (racked out), the shutter closes. When the circuit breaker is racked into the
“connected” position, the shutter opens, allowing the primary disconnects to make.

17. Classification of Circuit Breakers
Secondary Disconnects (stabs)
The secondary disconnects bring power from the control circuits into the circuit breaker. Photo shows an
LVPCB and its secondary disconnects. The typical arrangement for this breaker is to connect and disconnect
these stabs as the breaker is racked in and out of its cubicle. Photo shows the typical arrangement for an
MVACB, which often has to be manually connected.
Ground Disconnect (contact shoe)
The frame of the circuit breaker must be connected to the ground bus so that a short circuit or fault will be
taken to ground immediately and allow the protective devices to operate as quickly as possible. The ground
disconnect connects the frame of the circuit breaker to the ground bus. The ground disconnect is the first
connection made when racking a breaker in and is the last connection broken when racking it out. This
ensures that the frame of the breaker is grounded whenever there is a possibility of the frame being
energized

18. Classification of Circuit Breakers
Secondary Disconnects (stabs)
The secondary disconnects bring power from the control circuits into the circuit breaker. Photo shows an
LVPCB and its secondary disconnects. The typical arrangement for this breaker is to connect and disconnect
these stabs as the breaker is racked in and out of its cubicle. Photo shows the typical arrangement for an
MVACB, which often has to be manually connected.
Ground Disconnect (contact shoe)
The frame of the circuit breaker must be connected to the ground bus so that a short circuit or fault will be
taken to ground immediately and allow the protective devices to operate as quickly as possible. The ground
disconnect connects the frame of the circuit breaker to the ground bus. The ground disconnect is the first
connection made when racking a breaker in and is the last connection broken when racking it out. This
ensures that the frame of the breaker is grounded whenever there is a possibility of the frame being
energized

19. Classification of Circuit Breakers
Arcing Contacts
Arcing contacts are designed to prevent the main contacts from being damaged and can be made of alloys
of silver, cadmium, tungsten, and zinc. The tungsten, cadmium, and zinc make the arcing contacts harder, so
when the contacts open and close they will not deteriorate as quickly. When the circuit breaker opens, the
main contacts part first and then the arcing contacts part, drawing the arc across them. When the circuit
breaker closes, the arcing contacts make first, again drawing the arc across them. This prevents the main
contacts from carrying the arc and preserves them.
The contact surfaces are shaped so that they have a rubbing motion, referred to as “wipe.” Wipe helps clean
the contact surface, and is caused by one of the contact surfaces being contoured and the other surface
being flat. When the contacts close, the contoured surface will have a wiping motion against the flat surfaced
contact. Arcing contacts will usually have an arcing “horn” on the very top of the contact structure. The arcing
horn aids in transferring the arc from the arcing contact to the arc runner in the arc chute.
Main Contacts
The main contacts are constructed of a softer alloy using less tungsten or zinc and more silver. They carry
the load current, so they must have a lower resistance to current flow. The mains are larger, which also
decreases their resistance.
Auxiliary Contacts
Auxiliary contacts control electrical functions within the circuit breaker, such as turning the spring-charging
motor on and off at the appropriate times. On LVPCBs, auxiliary contacts are mounted on the frame of the
breaker (Photo 8 at right). Medium-voltage metal-clad switchgear will typically have the auxiliary contacts
mounted in the switchgear, rather than the breaker frame. Auxiliary contacts are mechanically driven from
the operating mechanism and are used for control and indicating circuits. They are connected to the
operating mechanism by a linkage and operate at the same time the main contacts do.

20. Classification of Circuit Breakers
Arc Extinguishers
Arc extinguishers (arc chutes) contain the arc, stretch it out, cool it, and deionize it. This occurs
within one-tenth of a second or less and is critical to safe operation of the circuit breaker and power
system. The time it takes to interrupt an arc is known as the “maximum total clearing time” — the
time from the start of the arc until it is completely extinguished. This characteristic is used to
properly coordinate power systems so they will trip in the right sequence (selective tripping).
Selective tripping is also referred to as “power system coordination,” as the devices will operate in
their proper sequence when this is performed correctly.
When the contacts begin to open, the hot arc will rise. Most air circuit breakers will have their arc
chutes positioned above the contact assemblies, as the natural tendency of the arc is to rise and
aid in extinguishing the arc. The arc is hurried along the process by various components in the arc
chute, such as puffers, blowout coils, arc runners, and arcing horns.

21. Classification of Circuit Breakers
Breaker closed current flowing through the contacts.
Main contacts open arc contacts are closed.
Small arcs are stretched into loops where it is cooled

22. Classification of Circuit Breakers
Arcing contacts separate and arc strikes
The arc transfers to the runners.
The arc is transferred to splitter plates to form
a number of short series arcs.

23. Classification of Circuit Breakers
The arc is extinguished.

24. Classification of Circuit Breakers

25. Classification of Circuit Breakers
VCB
An alternative that has virtually replaced MVACBs is the MVVCB. Vacuum circuit breakers
interrupt the arc by denying it air. In a pure vacuum, there can be no arc. Even though the
vacuum in vacuum bottles is very good, it isn’t perfect — so some arcing does take place.
The arc is interrupted very quickly, usually in two to three cycles, depending on the
application. Photo given below is a vacuum bottle cut-away to show its components.
Vacuum bottles require very little maintenance when compared to air-magnetic contact
assemblies. The contact moves only about ½ in. in the vacuum bottle, and the opening
springs are much lighter. This reduces wear on the assembly and also reduces the weight,
because heavy metal supports and frame can be decreased. The primary components of a
vacuum bottle include:

26. Classification of Circuit Breakers

27. Thank You