A motor Starter is a device or group of devices that serves to govern in some predetermined
manner the performance of an electric motor. A motor controller might include a manual
or automatic means for starting and stopping the motor, selecting forward or reverse rotation,
selecting and regulating the speed, regulating or limiting the torque, and protecting against
overloads and faults.
In this video we will go to show you different types of Motor starter or Motor controller.
There are we discuses popular four types of starters.
1. Direct On Line (DOL) starter. 2. Star delta starter.
3. Auto transformer starter. 4. Electronic Soft starter.
Direct on Line DOL starter.
A direct on line or across the line starter applies the full line voltage to the motor
terminals, the starters or cubicle locations can usually be found on an ELO drawing. This
is the simplest type of motor starter. A D O L motor starter also contains protection
devices, and in some cases, condition monitoring. The simplest form of motor starter for the
induction motor is the Direct On Line starter. The DOL starter consist a MCCB or Circuit
Breaker, Contactor and an overload relay for protection. Electromagnetic contactor which
can be opened by the thermal overload relay under fault conditions.
Star delta starter.
The Star Delta Starter is a very common type of starter and is used extensively as compared
to the other type of starting methods of the induction motor. A star delta is used for
a cage motor designed to run normally on the delta connected stator winding.
This is the reduced voltage starting method. Voltage reduction during star-delta starting
is achieved by physically reconfiguring the motor windings as illustrated. During starting
the motor windings are connected in star configuration and this reduces the voltage across each winding.
After a period of time the winding are reconfigured as delta and the motor runs normally. Star
Delta starters are probably the most common reduced voltage starters. They are used in
an attempt to reduce the start current applied to the motor during start as a means of reducing
the disturbances and interference on the electrical supply.
Auto transformer starter.
An Auto transformer Starter is suitable for both star and delta connected motors. In this
method, the starting current is limited by using a three-phase auto transformer to reduce
the initial stator applied voltage. The operation principle of auto transformer
method is similar to the star delta starter method. The starting current is limited by
reduce the initial stator applied voltage.
The auto transformer starter is more expensive, more complicated in operation and bulkier
in construction when compared with the star delta starter method.
But an auto transformer starter is suitable for both star and delta connected motors,
and the starting current and torque can be adjusted to a desired value by taking the
correct tapping from the auto transformer.
Electronic Soft starter.
A motor soft starter is a device used with AC electrical motors to temporarily reduce
the load and torque in the power train and electric current surge of the motor during
start-up. A start voltage is applied with time, irrespective
of the current drawn or the speed of the motor. For each phase two SCRs are connected back
to back and the SCRs are conducted initially at a delay of 180 degrees during the respective
half wave cycles. This delay is reduced gradually with time until the applied voltage ramps
up to the full supply voltage. This is also known as Time Voltage Ramp System. This method
is not relevant as it doesn't actually control the motor acceleration.
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