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Power Factor Correction On Delta Star Motor Connections


Len Fry

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I am considering power factor correction capacitors on a 200 HP US motor that was originall used in Brazil. There are a number of smaller motors hooked up like this at this facility as well. The motor is a Delta - Wye start configuration with 12 lead connection. First of all, I'm not sure I understand the purpose for the 12 leads. Nine of them are wired up. There are four sets of contactors, three of which are in when the motor is running. The PF correction should be installed downstream of the contactor. The question is which one or all? Can I parallel a single unit with more than one contactor? I have a connection drawing I could fax to anyone who would be kind enough to help me with this.

 

Thanks in advance

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Hello Len

 

Welcome to the forum.

 

The first question that I would ask is : Is this a two speed application? Sounds to me like it may be, in which case the correction is a little more complicated.

 

The easiest way to connect the correction, is to use a separate contactor for the correction capacitors, and only close this contactor when the motor is operating at the highest speed. You should be able to use auxiliary contacts off the last contact to close to bring this contactor in.

Thisa will result in no correction at low speed (assuming that it is a two speed application) but that is not an issue as your tariff is oriented to preventing maximum current, not minimum current.

 

Best regards,

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Hello Len

 

Welcome to the forum.

 

The first question that I would ask is : Is this a two speed application? Sounds to me like it may be, in which case the correction is a little more complicated.

 

The easiest way to connect the correction, is to use a separate contactor for the correction capacitors, and only close this contactor when the motor is operating at the highest speed. You should be able to use auxiliary contacts off the last contact to close to bring this contactor in.

Thisa will result in no correction at low speed (assuming that it is a two speed application) but that is not an issue as your tariff is oriented to preventing maximum current, not minimum current.

 

Best regards,

 

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Hi Mark,

 

Thanks for the input. I think I have figured it out. I went to a website for US motor and found the 12 lead configuration. The motor is as I thought a Wye start Delata run. Once I drew it all out it became obvious where the PF correction should be applied. One contactor sets up the start winding configuration. The other three set up the run configuration. There is still only one run line contactor. Thanks for your input. It's nice to know that there is someone that can help with some of the apparently mystical nuances in the electrical world.

 

Len

 

Hello Len

 

Welcome to the forum.

 

The first question that I would ask is : Is this a two speed application? Sounds to me like it may be, in which case the correction is a little more complicated.

 

The easiest way to connect the correction, is to use a separate contactor for the correction capacitors, and only close this contactor when the motor is operating at the highest speed. You should be able to use auxiliary contacts off the last contact to close to bring this contactor in.

Thisa will result in no correction at low speed (assuming that it is a two speed application) but that is not an issue as your tariff is oriented to preventing maximum current, not minimum current.

 

Best regards,

 

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