ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Questioning the electrical norms
by HotLine1 - 03/04/21 12:35 PM
Lock-down Thread
by gfretwell - 03/03/21 12:38 PM
Northern Tool Recalls Powerhorse Generators
by Admin - 02/25/21 09:49 PM
You will never guess
by gfretwell - 02/25/21 07:48 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 14 guests, and 18 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
75KVA Auto Transformer #181422 10/07/08 11:36 AM
Joined: Jun 2007
Posts: 106
M
mr_electrician Offline OP
Member
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 11:49 AM
Joined: Jun 2006
Posts: 613
M
mikesh Offline
Member
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 11:50 AM
Joined: Jun 2007
Posts: 106
M
mr_electrician Offline OP
Member
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:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
pcsailor
pcsailor
Minneapolis, MN, USA
Posts: 21
Joined: September 2019
Show All Member Profiles 
Top Posters(30 Days)
Popular Topics(Views)
275,704 Are you busy
209,627 Re: Forum
196,966 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3