Presentation on starter

Prepared By:
 M. AFTAB ALAM 2097-FET/BSEE/F-13
Course Instructor:
DR.SUHEEL ABDULLAH

Faculty of Engineering and Technology
Department of Electronic Engineering
International Islamic University,
Islamabad
 aftabalam2097@gmail.com

Need of starter
A starter is needed for a three phase induction motor
because at the time of starting, if induction motor is
started directly, it will draw large amount of current
which causes damage to adjoining equipments.
Thus, a starter is needed in order to limit the starting
current.
If a rated stator voltage is applied to the motor at the time of
starting, then the motor will draw heavy starting current.
This will increase i2R losses in the winding which will overheat
the motor.

The heavy starting current may damage the motor windings
Starter means at the time of starting our motor takes more
current due to high EMF in starting so its function is to
limit the starting current. we know in starting motor takes
5 to7 times current of rated current.
In order to avoid these problems, we can use some kind of a
starter to start the induction motor safely.

 Stator resistance starter
 Auto transformer starter
 Star-delta starter
 Rotor resistance starter
 Direct on line (DOL) starter
TYPES OF STARTER

A starter resistance is connected in each line in series with each
phase winding of the stator.
Initially all the starter resistance are kept in “Start” position so
that they offer their maximum resistance .
The switch is turned ON to connect the three phase AC supply
to the stator winding.
Due to starter resistance in series, each phase winding will
receive a reduced voltage. Due to reduction in the value of V1 , the
starting current is limited to a safe value.
As the motor accelerates, the starter resistance is reduced by
moving the variable contact of the resistance towards the “Run”
position.
In the “Run” position, the starter resistance is shorted out and
full stator voltage is applied across the stator winding.

Advantages and
disadvantages
 The starter is simple in construction and cheap.
 It can be used for both star and delta connected
stator.
 There are large power losses due to resistances.
 Also the starting torque of the motor reduces due
to reduced voltage applied to the stator.

. AUTO-TRANSFORMER STARTER
An autotransformer is used to apply a low voltage to the stator winding
at the time of starting. When the motor speed reaches the desired level,
autotransformer is disconnected and motor is connected directly across
the supply.
 The stator of the motor is connected through a 6-way double throw
switch.
 While starting, the switch is thrown to ‘Start’ side so that a reduced
voltage is applied to stator. This keeps the starting current safe limits.
 Once motor take up the speed, the switch is throw to ‘Run’ side so
that full supply voltage is applied to stator.
 A specific advantage of this starter is that reduction in voltage during
starting, can be done to any desired level by selecting proper tapping
of the autotransformer.

 This starter is used with a wound rotor induction motor. It
uses an external resistance/phase in the rotor circuit so that
rotor will develop a high value of torque.
 High torque is produced at low speeds, when the external
resistance is at its higher value.
 At start, supply power is connected to stator through a three
pole contactor and, at a same time, an external rotor
resistance is added.

The high resistance limits staring current and allows the motor to
start safely against high load.
Resistors are normally of the wire-wound type, connected through
brushes and slip rings to each rotor phase. They are tapped with points
brought out to fixed contactors.
As the motor starts, the external rotor resistance is gradually cut out
of circuit ; the handle or starter is turned and moves the three contacts
simultaneously from one fixed contact to the next.
The three moving contacts are interconnected to form a start point
for the resistors.

Star Delta Starter
 Most induction motors are started
directly on line, but when very
large motors are started that way,
they cause a disturbance of voltage
on the supply lines due to large
starting current surges.
 To limit the starting current surge,
large induction motors are started
at reduced voltage and then have
full supply voltage reconnected
when they run up to near rotated
speed.

D.O.L.(direct on line) starter

A Starter Which Connects A Motor Directly
Across The Line Is Called D.O.L. Starter.
In This Method, The Motor Is Connected By
Means Of A Starter Across The Full Supply
Voltage.
It Is Very Simple, Inexpensive, Easy To Install And
Maintain.
It Consist - START Button
- OFF Button
- Overload Relay
Switching By This Starter Is Directly From Line
Without Any Provision To Control The Starting Current
i.e. There Is No Device To Reduce The Starting Current
In This Starter.

SOFT STARTERS
 Soft-Starter is an
electronic starter
designed to
accelerate, de-
accelerate three-phase
induction motors and
to control the voltage
applied on the motor
during start and stop.

Block Diagram
 Starting Principle of Soft Starter
By using six SCR’s in a back to back configuration
, the soft starter is able to regulate the voltage
applied to the motor during starting from 0 volts
up to line voltage.
Feedback from the motor to the logic circuit used
to control the SCR firing for stabilization of motor
acceleration
 Frequency do not change as in VFD
 Only the voltage and current changes.

Difference between DOL/Star delta
/Autotransformer

Presentation on starter

More Related Content

What's hot

Viewers also liked

Similar to Presentation on starter

Recently uploaded

Presentation on starter