Youtube daily motor Aug 29 2017

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 give you a brief

overview of 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.

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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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