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#129776 - 08/18/05 06:05 PM Power Factor  
Dnkldorf  Offline
Member
Joined: Dec 2004
Posts: 1,064
nowhere usa
How does a Delta vs Wye change PF?

Any clues?


Dnk.....


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#129777 - 08/18/05 10:53 PM Re: Power Factor  
Bob  Offline
Member
Joined: Feb 2002
Posts: 182
Mobile, AL, USA
How does a Delta vs Wye change PF?
It doesn't. Load has a specific PF. Voltage has nothing to do with it. A motor generally has a lagging PF and a capacitor has a leading PF. Check Here for more info. http://www.ibiblio.org/obp/electricCircuits/AC/AC_11.html


[This message has been edited by Bob (edited 08-18-2005).]


#129778 - 08/19/05 06:53 AM Re: Power Factor  
Dnkldorf  Offline
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Joined: Dec 2004
Posts: 1,064
nowhere usa
That's what I thought too.

I am doing PF testing and harmonics testing with a Fluke 434, and downloaded the new firmware to correct some bugs in it.

On a 480X240/120ct transformer I am monitoring, if you switch from delta to wye on the Fluke, the PF changes from .67 to .94.

I am curious why, they should be the same measurements unless somehow they get measured differently in the meter.

But that makes no sense..

Thanks.

Dnk.....


#129779 - 08/19/05 07:18 AM Re: Power Factor  
Dnkldorf  Offline
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Joined: Dec 2004
Posts: 1,064
nowhere usa
Or is it a Phase-Line PF, and then a Phase-Phase PF?

That would make sense, wouldn't it?


Dnk..


#129780 - 08/19/05 07:34 AM Re: Power Factor  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
Only if the 'delta' connection tells the meter that the current sensors are in the phase to phase circuits, but the voltage connections are being made at the terminals.

Once you have the three conductors coming off the transformer, the power factor measurement should be the same.

-Jon


#129781 - 08/19/05 02:03 PM Re: Power Factor  
Ron  Offline
Member
Joined: Mar 2002
Posts: 582
White Plains, NY
A delta to wye transformer doesn't change the PF, but depending on how the meter makes the PF measurement, you may need to know that the delta to wye windings result in a 30 degree phase shift from primary to secondary.
Since PF is essentially measuring phase shift of voltage relative to current, that setting you describe on the meter may effect the reading.


Ron

#129782 - 08/19/05 03:41 PM Re: Power Factor  
Dnkldorf  Offline
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Joined: Dec 2004
Posts: 1,064
nowhere usa
It must be the phase-line reading, I measured another trans today and switched from delta-wye and the PF readings were about the same.

I will contact Fluke and let you know if your still interested.

Thanks for your help.

Dnk.....



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