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Soft Start

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#1 beddycor


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Posted 13 September 2008 - 07:11 PM

I am considering replacing a stare delta starter on a centrifugal fan using a 15 HP motor with a soft start. Having looked at quite a bit of information I am failing to understand how you can obtain the required speed and torque using soft start in the star configuration when you will only have 250V across each motor winding.

I can see that the required speed and torque can be obtained in delta mode but this is more complicated and appears to be less populer.
Can any one explain?


#2 marke


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Posted 14 September 2008 - 06:31 PM

Hello beddycor

Welcome to the forum.

You are correct, you can not develop enough torque in star with a soft starter if the motor is designed to be connected in delta.

You must connect the motor in the configuration that it is designed to run in.
If you are replacing a star delta starter, then the motor is designed to run in delta, so you permanently connect it in delta and then apply the soft starter.

Best regards,

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