WYE-DELTA
- Thread starter domnic
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charlie
Senior Member
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- Indianapolis
Re: WYE-DELTA
Dig out you motor books from when you went through the apprenticeship program. It has to be explained with diagrams. Ed can possibly do it but it would take a lot of words to explain it without diagrams.
Basically, the motor windings are across a lower voltage in the wye (? to N) so it doesn't draw as much current. After a few seconds, the starter will change the connection to a delta so the motor windings are now getting full voltage (? to ?) and it runs at full power.
The intent is to keep from dimming everyone's lights and causing other voltage dip problems.
Dig out you motor books from when you went through the apprenticeship program. It has to be explained with diagrams. Ed can possibly do it but it would take a lot of words to explain it without diagrams.
Basically, the motor windings are across a lower voltage in the wye (? to N) so it doesn't draw as much current. After a few seconds, the starter will change the connection to a delta so the motor windings are now getting full voltage (? to ?) and it runs at full power.
The intent is to keep from dimming everyone's lights and causing other voltage dip problems.
Re: WYE-DELTA
Domnic I just want to add to Charlies post. Sometimes starting torque is also an issue. I have worked with three phase motors with all twelve leads brought out. I believe this can be done with six lead motors also. As charlie mentioned one contactor closes and 277 volts starts the motor and after a few seconds the second contactor closes and full voltage is applied to the motor if the motor is 480 volts. I know of an installation where a large senior housing complex installed a 150 hp fire pump at 208 volts. the fire pump controller has a wye-delta starter. This was probably a case of concern of lights dimming as Charlie said. But along with reducing the voltage at the motor stating the stating touque is reduced also. With a voltage reduction of 58% which a wye-delta starter reduces the voltage, the starting torque is reduced 33%.
Herb
Domnic I just want to add to Charlies post. Sometimes starting torque is also an issue. I have worked with three phase motors with all twelve leads brought out. I believe this can be done with six lead motors also. As charlie mentioned one contactor closes and 277 volts starts the motor and after a few seconds the second contactor closes and full voltage is applied to the motor if the motor is 480 volts. I know of an installation where a large senior housing complex installed a 150 hp fire pump at 208 volts. the fire pump controller has a wye-delta starter. This was probably a case of concern of lights dimming as Charlie said. But along with reducing the voltage at the motor stating the stating touque is reduced also. With a voltage reduction of 58% which a wye-delta starter reduces the voltage, the starting torque is reduced 33%.
Herb
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