ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Recent Posts
Green House wiring
by gfretwell. 07/20/17 12:39 AM
1913 American Electrician's Handbook
by Admin. 07/19/17 08:41 PM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
210.70 / Wall Switch / When adopted?
by HotLine1. 07/16/17 11:25 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,163 Are you busy
174,542 Re: Forum
166,984 Need opinion
Who's Online Now
1 registered members (Potseal), 44 guests, and 9 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#26924 - 06/26/03 08:25 AM transformer question  
sparky806  Offline
Member
Joined: Dec 2002
Posts: 59
Shawnee, KS, USA
does anybody here have expereance with back feeding transformers? here's the deal...i have a customer with a 240 volt grounded b 3 phase service. he has an x-ray machine that requires 480 volt. i am going to install a 480 t0 240 volt transformer. i know if i back feed it, i will get the needed 480 volts, but i'm not sure on conductor sizing. is it the same as a normal install? is there anything else i should be aware of? Thanks
richard


Work Gear for Electricians and the Trades

#26925 - 06/26/03 01:56 PM Re: transformer question  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
'806 — It's duck soup. Get a 480∆-240∆ dry-type transformer...15kVA and up are fairly common.

If you don't mind a 2MB pdf, see page 21 at http://www.federalpacific.com/literature/drytrans/FPTS-RTB-0701.pdf

Suggest getting a transformer with both FCAN and FCBN taps—they work in the opposite direction for a reverse-fed arrangement. For sensitive electronics, electrostatically shielded units are suggested. If heat is an issue…pick an 80°C-rise transformer on page 27.

For reverse-fed operation DO NOT connect the 240V-side X4 terminal to anything.

Overcurrent protection of 480V windings on a ∆-∆ transformer can be by the usual 125% rating on [only] the 240V source. No system grounding is required by NEC for the 480V side.

If you like, contact me off-board for figuring the kVA-rating, breaker/fuse and conductor sizes needed.


#26926 - 06/26/03 06:05 PM Re: transformer question  
sparky806  Offline
Member
Joined: Dec 2002
Posts: 59
Shawnee, KS, USA
bjarney
thanks. i'm gonna email you right now.
Richard



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: 0.014s Queries: 14 (0.002s) Memory: 0.7517 MB (Peak: 0.8771 MB) Zlib enabled. Server Time: 2017-07-20 12:39:07 UTC