# Calculating Of Currents In Dol And Star-delta?

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What are the formulae to calculate Line currents in DOL and star -delta starters?

How can we say that in star-delta starter the currents through the windings are 1/root3 of line current?

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• 2 weeks later...

Upon reaching rated speed, line current of motors using both direct online starter and star delta starter are the same.

I = P / sqrt(3) x U x cos a

I is the line current of the motor.

P is the input power to the motor. (Usually stated on the motor nameplate)

U is the line to line voltage.

cos a is the power factor of the motor. (Usually stated on the motor nameplate)

As for the star delta starter, during start

The line current is 1/sqrt(3) because the voltage is reduced by 1/sqrt(3) as the motor winding is in star configuration.

Regards,

Kana

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