ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by SteveFehr. 07/23/17 09:46 AM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,251 Are you busy
174,658 Re: Forum
167,076 Need opinion
Who's Online Now
2 registered members (SteveFehr, HotLine1), 61 guests, and 11 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
RH1
RH1
California
Posts: 22
Joined: August 2009
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.011s Queries: 14 (0.002s) Memory: 0.7590 MB (Peak: 0.8883 MB) Zlib enabled. Server Time: 2017-07-23 14:38:01 UTC