ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Air Compressor feeder conductor sizing
by Potseal. 01/15/18 09:08 PM
VDE 0100 to introduce AFCIs
by LongRunner. 01/15/18 11:38 AM
Under carpet cable?
by HotLine1. 01/15/18 09:57 AM
Any New Years Resolutions?
by Bill Addiss. 01/13/18 10:21 AM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 25 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Impedance matching on transformer banks #129992
12/27/05 07:56 PM
12/27/05 07:56 PM
W
WFO  Offline OP
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:
Re: Impedance matching on transformer banks #129993
12/29/05 01:31 AM
12/29/05 01:31 AM
D
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.

Re: Impedance matching on transformer banks #129994
12/29/05 07:04 AM
12/29/05 07:04 AM
W
WFO  Offline OP
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.

Re: Impedance matching on transformer banks #129995
12/29/05 03:37 PM
12/29/05 03:37 PM
D
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.


Featured:

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

 

Member Spotlight
HCE727
HCE727
Delaware County, PA, USA
Posts: 186
Joined: November 2005
Show All Member Profiles 
Top Posters(30 Days)
sparky 23
Admin 19
Potseal 13
Popular Topics(Views)
243,513 Are you busy
180,304 Re: Forum
170,802 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.049s Queries: 14 (0.004s) Memory: 0.9570 MB (Peak: 1.0875 MB) Zlib enabled. Server Time: 2018-01-16 21:05:16 UTC