ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Extension cords
by LongRunner. 05/25/18 12:19 PM
Fire source!
by LongRunner. 05/25/18 01:49 AM
Alternative income sources
by gfretwell. 05/24/18 10:07 PM
Furnace igniter leaking noise to stereo
by geoff in UK. 05/23/18 01:18 PM
Opinions Please
by Keith_Mc. 05/23/18 09:22 AM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 5 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
75KVA Auto Transformer #181422
10/07/08 12:36 PM
10/07/08 12:36 PM
M
mr_electrician  Offline OP
Member
Joined: Jun 2007
Posts: 106
London, Ontario
I have been asked to temporarly hook up a piece of equipment. It is 480V 3 phase and has 90A fuses on its main disconnect. The majority of the load is the electric heaters. I have a 75 KVA auto transformer (600/480) that I am going to use. We have a 600V service. I was wondering if anyone has had any issues trying to power up a 75KVA transformer with 60A primary fuses on it. I want to disconnect the electric heaters on the piece of equipment for now since we are onlyy worried about testing the other connected loads such as motors and I/O. This would leave a very small connected load but I am worried that the inrush of the transformer would blow the 60 amp fuses. Should I be safe and fuse it at 80 amps as if it were fully loaded?


Never trust an electrician with no eyebrows!!
Tools for Electricians:
Re: 75KVA Auto Transformer [Re: mr_electrician] #181448
10/08/08 12:49 PM
10/08/08 12:49 PM
M
mikesh  Offline
Member
Joined: Jun 2006
Posts: 613
Victoria, BC, Canada
I have an installation here that powers a 75 KVA transformer with 60A Time delay fuses The run to the transformer is long, more than 100 meters. 60 Amp fuses were chosen because the secondary powers a 200 amp panel and there is no secondary OC protection so 60 A was the biggest fuse that could match without another OC device on the secondary or a 225 amp panel. They have been operating for about 2 1/2 years without an inrush failure on these fuses. I do think the impedance of the run helps too

Re: 75KVA Auto Transformer [Re: mr_electrician] #181449
10/08/08 12:50 PM
10/08/08 12:50 PM
M
mr_electrician  Offline OP
Member
Joined: Jun 2007
Posts: 106
London, Ontario
So those who are interested know, I went ahead and strangled the 75KVA transformer primary to 60A and it held when I turned it on. So I guess now I can go ahead and start seeing what does and doesn't work on this boat anchor. Did I mention that it has sat for 2-3 years with no power to it. Allready I have to reload the plc program. Battery went dead!!


Never trust an electrician with no eyebrows!!

Featured:

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

 

Member Spotlight
sbi
sbi
indiana
Posts: 47
Joined: March 2008
Show All Member Profiles 
Top Posters(30 Days)
twh 11
Popular Topics(Views)
246,916 Are you busy
184,322 Re: Forum
173,529 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.020s Queries: 15 (0.004s) Memory: 0.9507 MB (Peak: 1.0750 MB) Zlib enabled. Server Time: 2018-05-26 08:22:34 UTC