The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Forum Software Upgrade coming soon...
by Ruben Rocha
Today at 07:36 PM
ESA Arc flash course
by frank
Today at 04:25 PM
Re: Fabricating Guards out of Lexan?
by frank
Yesterday at 04:11 PM
Would ELV branch circuits be a good idea?
by gfretwell
Yesterday at 01:26 PM
Why cables look like they do
by Texas_Ranger
Yesterday at 12:33 PM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Webmaster 27
HotLine1 21
Ruben Rocha 16
Trumpy 12
ghost307 12
Who's Online
2 registered (sparkyinak, Trumpy), 0 Guests and 226 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#130574 - 07/24/06 03:03 PM Double tapped secondary.
VAElec Offline
Member

Registered: 07/26/05
Posts: 48
Loc: Sterling, Virginia, US
Found a new transformer today. 480-208Y/120 with two sets of taps on the secondary, thirty degrees out of phase (0 degrees X1,120 X2,240 X3, XO then 30 X5,150 X6,270 X7, XO). Anyone seen this? From what I can figure it is supposed to cancel harmonics and reduce the need for an oversized neutral conductor. 1/0 with 3/0 neutral on the secondary, which differs from the size A mcm a,b,c size 2xA neutral for a K-rated transformer.

Anyone have an idea on how the coils are tapped? No namplate diagram.

(edited for coil question)

[This message has been edited by VAElec (edited 07-24-2006).]
_________________________
Pete

Top
#130575 - 07/24/06 07:49 PM Re: Double tapped secondary.
LarryC Offline
Member

Registered: 07/05/04
Posts: 782
Loc: Winchester, NH, US
Is this for using a 3 phase primary to create a single phase secondary?

Just like wiring a 12 lead 3 phase genny to get a single phase output at 2/3 of the rated output.

http://electrical-contractor.net/ubb/Forum15/HTML/000091.html

LarryC

Top
#130576 - 07/24/06 10:34 PM Re: Double tapped secondary.
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Does it look anything like this:



This is a "Rectifier Transformer" - part of an elaborate UPS System.

Although the one shown in the drawing does not have a 4 wire Wye Secondary scheme, all that is needed to make the Wye section a 4 Wire type is to tap into the "Common Jumper" which connects the left sides of each coil on the Wye side, and extend that tapped point with a suitable sized Conductor.

This is the way that _ALL_ 4 Wire Wyes are done.

The Delta winding is used for cancelling Harmonics. It is likely connected to some external load.

Need to refresh myself, by grabbing the Electrical Engineering Handbooks!


Here's another type of Rectifier Transformer I have run across:



This has Three (3) 3 Phase Secondaries - resulting in a 9 Phase Secondary Transformer.

These drawings are from the Technical Reference section, and may be found under the topic:

6 and 9 Phase Transformers

I thought I had uploaded some pictures of these Transformers, but not sure where and when - if at all!
Plan to make a new topic in the Technical Reference section tonight, which will have pictures of these "Specialty Transformers" I have come across. Once this is done, will reply to this thread with link(s).

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#130577 - 07/30/06 04:15 AM Re: Double tapped secondary.
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
***BUMP***

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#130578 - 08/03/06 05:16 PM Re: Double tapped secondary.
VAElec Offline
Member

Registered: 07/26/05
Posts: 48
Loc: Sterling, Virginia, US
This is a 3 phase primary, 3 phase (times two with 30 degree shift) secondary. It is delta/wye-wye. I think that it must look very much like the first image posted, but can't say for sure as the nameplate has info. The main thing I can think of is that both sets of secondary taps are 3P/4W wye.

I know almost enough about this type of transformer to give me problems.
_________________________
Pete

Top


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals