Answer / pramitha

A reduced voltage is applied at the starting,and the
voltage is increased to the rated value,when the motor has
picked up speed.the reduced voltage is obtained by using a
starter.

Answer / jitendra singh

control starting current and torque...... but current should not be controlled at the expense of torque....

Answer / vetriselvi

starters are used for reducing the starting currrent

Answer / suman

small induction motors up to 3H.P.,may directly be switched on to supply mains ,but those of larger capacity must use some type of starting device or starter.the function of starter is to limit the current at the time of start, which is about 5 times the full load current this excessive current has two major upsetting effects 1. it produces large voltage drop in the distribution network and causes voltage regulation of the supply system 2.it may cause disturbance in stopping of the motor which are already running on the same supply line Four types of starting methods are employed:
1.Star-Delta
2.Auto transformer method
3.Primary resistor starting.
4.Direct On-line.

Answer / vidyasagar

the current in an induction motor has the equation

i=sE/(r^2+(sx)^2)^0.5
at starting s=1
so sE=E
SO MAXIMUM EMF IS applied in the rotor circuit.hence maximum
current.to limit this high current a starter is used

Answer / angel

starter is required to limit the current and starting the
torque and also increases.

Answer / puja

to reduse the starting current ,so that no ohmic losses in
the windings

Answer / eugine augustine

Starters are used in Squirrel Cage Induction Motors for the
following reasons:-
1. To provide several switching on and off operations by
means of the Contactor whose special contacts can withstand
high starting currents and switching off surges.
2. To provide lower starting currents at starting for
larger HP Motors, thereby preventing severe voltage drops in
the line which may affect other running equipments.
3. To provide protection against overload and single
phasing by means of the thermal magnetic Overload relay
provided in the Starter.

Answer / sharif

at starting, The relative speed between the field and the stationery conductor (the rotor) is maximum and the resistance of winding is very small. If rated voltage is applied to the motor a current of 500%-800% of nominal current is drawn from the the supply. The starting current will be diminished when the rotor picks up speed. This high starting current will heat up the motor and may also damage insulation. The starting toque, which is proportional to the squared of the voltage will also be massive and might damage the load connected to the shaft of the motor. Another Important factor is the voltage dip in the network due to the sudden withdrawal of large current from the network. To overcome all these problems, a starter is used especially for big industrial motors. Factors, such as size of the motor, type of load, duty cycle and the environment are important when selecting a particular starter for a motor. The best starters are soft-starters and variable speed drives (V.S.D). With the use of VSDs, you can limit the starting current and also regulate the torque -speed characteristics of the motor as per requirements of the load.

Answer / divvela adhi sekhar

at the time of starting slip is maximum that is <1> and rotor speed is zero emf depends upon synchronous speed and actual speed generally this starting is 5 to 8 times of full load current. this current damages the circuit thats why the starter is required

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