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RJohnson
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Post subject: 3-Phase Transformer Model  Posted: Wed Jul 28, 2010 8:08 pm |
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Joined: Wed Jul 21, 2010 7:54 am
Posts: 4
Location: OK
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If I have a 300 kVA utility transformer bank made up of 3 single phase 100 kVA transformers each with an impedance of 1.9%, is the equivalent impedance of the 300 kVA transformer simply 3 x 1.9, or is it the square root of 3 times 1.9?
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jghrist
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Post subject: Posted: Thu Jul 29, 2010 9:51 am |
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Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
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RJohnson wrote: If I have a 300 kVA utility transformer bank made up of 3 single phase 100 kVA transformers each with an impedance of 1.9%, is the equivalent impedance of the 300 kVA transformer simply 3 x 1.9, or is it the square root of 3 times 1.9?
1.9%. The impedance is a per phase value.
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stevenal
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Post subject: Posted: Fri Jul 30, 2010 8:04 am |
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 631
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How are the transformers connected? Wye or delta?
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RJohnson
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Post subject: Posted: Sat Jul 31, 2010 10:42 am |
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Joined: Wed Jul 21, 2010 7:54 am
Posts: 4
Location: OK
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stevenal
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Post subject: Posted: Mon Aug 02, 2010 8:52 am |
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 631
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Edited: Sorry I misremembered. Connections make no difference. 1.9% using 100 kVA and line to neutral voltage to get ohms secondary equates to 1.9% using 300 kVA and line to line voltage.
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J.T
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Post subject: Posted: Tue Aug 03, 2010 6:38 am |
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Joined: Fri Jan 30, 2009 10:04 am
Posts: 10
Location: Toronto
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RJohnson wrote: Connected delta-wye.
No matter how the 3 single phase transformer connected, the impedance should be the same as the single phase tested value
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LarryJo
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Post subject: Posted: Tue Jun 07, 2011 12:32 pm |
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Joined: Mon Apr 13, 2009 11:54 am
Posts: 8
Location: Midland, Tx
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What is one of the transformers has a different nameplate impedance?
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stevenal
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Post subject: Posted: Fri Jun 10, 2011 8:35 am |
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 631
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Then there is no equivalent three phase impedance.
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J.T
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Post subject: Posted: Sun Jun 12, 2011 6:08 pm |
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Joined: Fri Jan 30, 2009 10:04 am
Posts: 10
Location: Toronto
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Can 3 single phase transformers with different IZ% be connected to a transformer bank?
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glen1971
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Post subject: Posted: Sun Jun 12, 2011 10:33 pm |
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Joined: Mon Mar 29, 2010 5:02 am
Posts: 136
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J.T wrote: Can 3 single phase transformers with different IZ% be connected to a transformer bank?
It is my understanding that they can be, but they still have to be within a very tight range..
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