ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Recent Posts
VFD MotorFeeders
by gfretwell. 10/19/17 01:02 AM
Generator Cable Sizing
by brsele. 10/18/17 07:39 PM
What do you do?
by gfretwell. 10/17/17 01:08 AM
Good ol' copper pipe in the fuse holder trick
by HotLine1. 10/16/17 07:16 PM
Another generator question
by HotLine1. 10/16/17 07:02 PM
New in the Gallery:
Gallery Test
Popular Topics(Views)
241,448 Are you busy
177,431 Re: Forum
169,014 Need opinion
Who's Online Now
0 registered members (), 48 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#129992 - 12/27/05 08:56 PM Impedance matching on transformer banks  
WFO  Offline
Member
Joined: Sep 2005
Posts: 202
Cat Spring, TX
First, I'm always getting asked by the linemen if they can bank an "X" impedance transformer with a "Y" impedance transformer. The old REA specs we have never even mention it except in the delta/delta configuration. So we (I) have always assumed that it doesn't matter in the wye/delta and wye/wye banks that we use. Is this true?

Secondly, when the REA specs DID refer to impedance balancing, they would say that the tansformers had to be within plus or minus "X" percent of each other. Were they referring to the "percent" as stamped on the nameplate, or an actual arithmetical percentage between the two (or three) values?


Tools for Electricians:

#129993 - 12/29/05 02:31 AM Re: Impedance matching on transformer banks  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
My notes state that the impedence of the transformers to be paralleled should be within 7-1/2% of each other so that they will share the load as close as possible.


#129994 - 12/29/05 08:04 AM Re: Impedance matching on transformer banks  
WFO  Offline
Member
Joined: Sep 2005
Posts: 202
Cat Spring, TX
Sorry, I didn't really word my question that well. I didn't mean paralleling them, just operating them together 3 phase banks.


#129995 - 12/29/05 04:37 PM Re: Impedance matching on transformer banks  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
My application notes state that a D-Y bank would share equally a balanced 3ph load even though the impedance of the individual transformers may not be equal. That identical transformers should be used in D-D and open D banks. Also, Y-Y should be avoided.



Member Spotlight
Attic Rat
Attic Rat
Bergen Co.,N.J. USA
Posts: 524
Joined: December 2003
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.011s Queries: 14 (0.003s) Memory: 0.7600 MB (Peak: 0.8893 MB) Zlib enabled. Server Time: 2017-10-22 22:57:20 UTC