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transformer help needed #187363 06/24/09 12:55 PM
Joined: Jun 2009
Posts: 2
J
jkmscottie Offline OP
New Member
I am trying to get from 208v with 2 wires to 240 on 1 wire to ground any ideas on how to achieve this?

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Re: transformer help needed [Re: jkmscottie] #187364 06/24/09 01:36 PM
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Posts: 9,571
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gfretwell Offline
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Greg Fretwell
Re: transformer help needed [Re: gfretwell] #187365 06/24/09 02:29 PM
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gfretwell Offline
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I just looked it up and they have 208 to 120/240 from 1 KVA to 75 KVA.
Search by keyword "208 primary" and look at the single phase units.
You don't say anything in your profile but I am assuming you know the ramifications of installing a transformer.


Greg Fretwell
Re: transformer help needed [Re: gfretwell] #187366 06/24/09 04:31 PM
Joined: Apr 2002
Posts: 7,235
HotLine1 Offline
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Are you sure you want "240 on 1 wire to ground"

240 is 2 'hots', 240 volt leg to leg, and 120 volt leg to ground and/or neutral.

Your profile says that you are an electrician, is that correct??



John
Re: transformer help needed [Re: HotLine1] #187368 06/24/09 06:32 PM
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Posts: 193
G
GA76JW Offline
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I'd be interested to hear what application you are using this for?????

I can't say as I have heard of anything that uses 240 on one leg yet.


"If common sense was common, everyone would have it"-not sure, someone here

Re: transformer help needed [Re: GA76JW] #187369 06/24/09 06:40 PM
Joined: Jun 2009
Posts: 2
J
jkmscottie Offline OP
New Member
Yes i am an electricain. I am working on a heater project for the company i am working for now. It is for leakage current testing on heaters. They specified and asked if i can get. I am told that an isolation transformer will do the job. Staco said they can do it. Just checking with you all to see what your opinions are on this.
Thank You

Re: transformer help needed [Re: jkmscottie] #187373 06/24/09 09:05 PM
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gfretwell Offline
Member
The transformers you get with a "208 primary" search (second pane down) are right up your alley. For test equipment you could even switch the output topology to test with 3 different grounding references.


Greg Fretwell
Re: transformer help needed [Re: gfretwell] #187374 06/24/09 09:24 PM
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twh Offline
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Why not a megger?

Re: transformer help needed [Re: twh] #187376 06/24/09 09:29 PM
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Posts: 9,571
G
gfretwell Offline
Member
WAG? Testing under normal load conditions?

BTW, you can get this at Grainger but you will save about 40% if you have your supply house order you one.

BTDT

Better feed the little guy anyway.


Greg Fretwell
Re: transformer help needed [Re: gfretwell] #187476 06/27/09 09:30 PM
Joined: Oct 2000
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Scott35 Online Happy
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jkmscottie

Welcome to ECN.

Obtain a "Standard", off-the-shelf Single Phase Isolated Transformer, which has a 208V Primary, and 240V Secondary.

Feed the Transformer with a normal 208V 1 Phase 2 Wire + EGC (Equipment Grounding Conductor) Circuit.

On the Secondary side, ground either one of the "X" Terminal outputs... for example, Ground "X2".

Now you have a 240V 2 Wire system with an Ungrounded Conductor and a Grounded Conductor.

The correct way to describe your desired 240V Circuit is:

240V 1 Phase 2 Wire Grounded Circuit.

One "Side" of the Circuit is Ungrounded ("Hot" to Ground),
The other "Side" of the Circuit is Grounded - just like the "Neutral" on a 1 Phase 3 Wire Circuit, or the Common "Neutral" on a 208Y/120V 3 Phase 4 Wire Circuit.

Match the KVA rating to the KVA requirement for the test loads. Since the test loads are Resistance type loads, the power ratings will (almost always) be in KW (Kilo Watts).
If the Heaters consist of only Heater Elements, then the KW ratings will equal KVA.

If these loads only have Ampere ratings, multiply the Amperes by 240, which will show the KW / KVA rating.
example:
Heater Element listed for 240V, FLA = 10
240 x 10 = 2400 VA (Volt-Amps)
Minimum KVA requirement: 2.4 KVA
Transformer size: 3.0 KVA

Good luck.

Scott


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

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