Why star delta starter prefer to D.O.L starter for large motors?

We prefer star delta starter for reducing start voltage but Normally in D.O.L starter-motor is always connected in star - it will also start in reduced voltage.... Explain

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In large motors: when motor start it draws a large current in starting , so we use star delta method to reduce this current in starting by
Firstly we connect motor on Start (motor no loaded) on low voltage (ex 220 v in 220/380 v system) so, current reduce.

Secondly, motor must running at normal speed to run on load then we change to delta method and running on normal voltage.
DOL not used at large motor because of high starting current that cause burning motors windings and cause under voltage that consider a big problem for other devices.

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saeed iqbal

  • Jul 24th, 2015

In starting motor gets 3 to 4 times more current then its normal current. So we use star delta starter to limit the starting current of the motor with the help of star circuit.when motor will run in the normal position so the circuit of the motor will change to delta circuit with the help of centrifugal switch. So now motor will get rated current b/c motor is now connected in delta. Now motor will give more speed and torque

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