ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
High current GFI vs regular GFCI
by gfretwell. 11/16/18 01:45 AM
This anti-theist is priceless!!!
by djk. 11/14/18 07:19 AM
Single phase and what you call it.
by dsk. 11/12/18 11:10 AM
220/230/240V 60Hz Systems
by Albert. 11/07/18 12:48 AM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
0 registered members (), 27 guests, and 25 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Choking Transformers #171424
11/27/07 09:59 PM
11/27/07 09:59 PM
M
mr_electrician  Offline OP
Member
Joined: Jun 2007
Posts: 106
London, Ontario
Hello, can someone tell me what it means to choke a transformer and the theory behind it. When would you do this and why?


Never trust an electrician with no eyebrows!!
Tools for Electricians:
Re: Choking Transformers [Re: mr_electrician] #171439
11/28/07 09:12 AM
11/28/07 09:12 AM
G
ghost307  Offline
Member
Joined: May 2005
Posts: 959
Chicago Illinois USA
The OCP requirements give the maximum rating that can be used to protect a transformer.

In the case of a recent design here, the load was just beyond the capacity of a 300KVA transformer, but the next size is 500KVA.
In order to avoid the costs and physical size of the OCP on both sides of the transformer, it was fused at something less that the Code maximum. Since that will also limit the secondary side current, the smaller distribution equipment can be used on that side as well. I rarely choke a transformer, but sometimes the big jump in sizes for the big ones get to be problems. In this case, I would have needed a 350KVA transformer (if anybody sold one), but I was able to choke a 500KVA without having to use the maximum OCP sizes in the design.


Ghost307

Featured:

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

 

Member Spotlight
Grover
Grover
Sebago, ME, USA
Posts: 109
Joined: January 2005
Show All Member Profiles 
Top Posters(30 Days)
Admin 8
Popular Topics(Views)
251,506 Are you busy
188,682 Re: Forum
178,386 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.016s Queries: 15 (0.003s) Memory: 0.9424 MB (Peak: 1.0614 MB) Zlib enabled. Server Time: 2018-11-16 13:54:14 UTC