isolation transformer, which one??

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vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

isolation transformer, which one??

Post by vibrations1951 »

Hello again. Been a while since I've posted but have been reading posts regularly. I've been quite busy for the past year plus, just trying to get the shell up and heated to the studio build. See vibrationsrecording.com even though I haven't updated it for a while now. anyway, time to get some ac power in there.

I'll be bringing in single phase 200amps 60hz ac (local co. wouldn't do three phase even though it's a commercial service). My wife and I share the building so she gets 100amps "dirty power" to her piece (I'm also going to use that feed for my "dirty power"). I'm running the other 100amps to a "clean power" panel in my machine room.

Both 100A feeds off the 200amp service will carry all three wires (2 hot and the neutral) to each respective 100amp breaker box. To make mine a "clean box" I want to put an isolation transformer in line before the "clean" box in my machine room to break the "dirty" ground.

My sparky agrees that a single phase, 15kva (80% loss typical), 240/120V 100amp in and 240/120V 100amp out is desireable. This leaves plenty of room for eventual/possible growth even though I don't anticipate needing more than 60 amps total full bore at this time.

The electrician suggested I find the right unit and he would graciously order for me so that i can pay his cost only. He's delt with these for cows/farms, not recording studios, though there may be no difference for all we know???Problem is, I've been researching for weeks now online and don't seem to be able to decide which brand/which type of isolation transformer to buy?? The furman rigs look great but i want just one to hardwire inline before the breaker box. the furman rig and others are too small and designed for after the box.

So.....Toroidal iso trans., sheilded,...... Acme, Temco, GE, TSI power, Hammond power, Piltron, others???... I'm in need of some direction, suggestions???? I see many companies build to order though "of the shelf "would likely be less costly.

You guys have been a great resource before and i hope you can help on this one.
NAMASTE
Speedskater
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Location: Cleveland, Ohio, USA

Re: isolation transformer, which one??

Post by Speedskater »

Gee, nobody had an answer! In the past I always got transformer from the surplus shops. But that was then and this is now.
If you do get a transformer, I think that I would wire it 240V input with two 120V outputs wired in parallel (through a 6 throw breaker box) so that all the equipment is on the same phase or leg of AC power.
Kevin
vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

Re: isolation transformer, which one??

Post by vibrations1951 »

wire it 240V input with two 120V outputs wired in parallel
Hey speedskater, thanks for replying. I also posted on Rod's forum so perhaps others replied there. Anyway, your suggestions are right on. Here's what I've pretty much settled on:
Toroidial Isolation Transformer with shield
Input 240V
Output 240V, 40A, 60Hz
Center Tapped

The electrician said this will give us the ability to hook the secondary winding to our studio subpanel and get 80A-total @120V 60Hz single phase from the subpanel (40A on each leg of the panel I believe). It will all be the same phase but on two legs of the subpanel.

Here are a couple of links that might be helpful for others.


http://www.zycon.com/Products/Transform ... 5Qod4Vck2A
http:/www.toroid.com
http://www.equitech.com/products/indust ... oroid.html

Thanks again for the reply, wish me luck! ciao, jp
NAMASTE
Speedskater
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Location: Cleveland, Ohio, USA

Re: isolation transformer, which one??

Post by Speedskater »

If the transformer's secondary is center-tapped, rather than having two separate windings you won't be able to wire them in parallel. That is have two 120V output on the same leg or phase.
Kevin
vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

Re: isolation transformer, which one??

Post by vibrations1951 »

:? I'm definately in over my head. OK, here goes. Hope this translates well.(please note that the verticle dashed lines are supposed to be solid) The "Schematic" says:

Primary Secondary

0V BLACK ____ l : ___ 1 BLACK 120V RMS / 40A RMS
l l : l UO = 121.2V RMS
l l : l
240V BLACK ____l l : l___ BLACK 0V
l : l
l : l UO – 121.6V RMS
l : l___2 BLACK 120V RMS / 40A RMS
l :
l :........ GREEN STATIC SHIELD


PRIMARY LEADS TO BE INSIDE A SLEEVE.
-----------------------------------------------------------------------
NOMINAL SUPPLY: 240V +/-10%
RATED PRIMARY CURRENT: 40.4A
RATED FREQUENCY: 60 Hz
TEMP. RISE AT RATED LOAD: 62 ºC
DIMENSIONS/WEIGHT: MOUNTING: CORE DATA:
WxLxH: 16x16x16” MOUNTED IN SIDE NEMA 1 CORE # 908776
FLOOR STAND STEEL ENCLOSURE CORE LOSS = 37 W
WEIGHT = 155 LBS. NO-LOAD CURRENT = 323 mA
Dimensions stated above are nominal. Tolerance is 10%.
OTHER SPECIFICATIONS: Transformer meets UL 506 and CSA C22.2 No. 66 standards.
ROHS compliance. Class B insulation. SAll leads to be terminated with terminal blocks.
------------------------------------------------------------------------------------------


Soooooo...is this center tapped or did I misslead you speedskater? Does this look like it is correct for my purposes?? I haven't quite finalized the deal yet so your thoughts are very much needed at this time. Thanks so much. I don't want to make a mistake with something so important and non-returnable to boot!!
NAMASTE
vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

Re: isolation transformer, which one??

Post by vibrations1951 »

OOPS! The formatting changed when I submitted. The OV and 240V are the primary side. the 2-120V, 40A, 60Hz are on the secondary as follows: 120V-OV-120V and the ground connected to the static shield between the primary and secondary. What a mess. I have this in PDF format but don't know how to get it on the forum. I could email it I guess. :roll:
NAMASTE
Speedskater
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Re: isolation transformer, which one??

Post by Speedskater »

Most forums use software that reformat text massages with too many spaces.
Do you have a part number for the transformer, that can be looked up on-line?
Kevin
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Re: isolation transformer, which one??

Post by Speedskater »

Does it look like either of these transformers?
Kevin
vibrations1951
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Re: isolation transformer, which one??

Post by vibrations1951 »

I don't have a part # because it was designed for me alone by Toroid.
The top shematic looks close!

In the basic schematic Toroid sent the primary 0V is on top and the 240v below. I don't know that this matters but thought I should mention it. I don't know what the 2 dots on the primary and 2 on the secondary in your schematic are but in Toroid's there is no equivalent.

the secondary is nearly identicle except for the aforementioned dots and that the 2-120v are RMS not "b" and further, ea. 120V RMS states UO=121.2V RMS

And, my schematic also shows the static shield in between the primarys on the secondary side and a "Green" lead on the secondary side for that, not connected physically to anything else.

I hope this helps clarify and not confuse matters. Thanks for the quick response. Look forward to your advice! ciao, jp
NAMASTE
Speedskater
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Re: isolation transformer, which one??

Post by Speedskater »

Let's see:
If we flip my schematic upside down the voltage numbers are correct. That's OK no difference.
The small black dots are often reference colors or marks on the windings often indicating the hot lead. So that the voltage don't fight each other.
The small "a" and "b" are the AC power phases or legs. It's 204V from "a" to "b".
I didn't include the shield and/or safety ground in my drawing because I would have to guess on just how they were wired.
Kevin
vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

Re: isolation transformer, which one??

Post by vibrations1951 »

OK, I think...maybe not. So are you saying my proposed transformer will work effectvely or is it a problem? is my schematic representing "center tapped"?
If the transformer's secondary is center-tapped, rather than having two separate windings you won't be able to wire them in parallel. That is have two 120V output on the same leg or phase.
With my limited understanding looks to me like my setup gives me 120V, 40A, 60Hz single phase on each of the legs (if I'm using the right term) from the secondary. Does this mean that with my setup I have two opposing phases?

Then wiring each of these respectively to each bar of my subpanel, (the transformer secondary neutral to neutral of the subpanel as well) , I will have 80A available single phase (40A on each breaker box leg) and even though it's single phase, they are opposing single phases? have I got this right??? as lost as I feel, I must be getting close to understanding, I hope...

So then it might follow that if equipment circuts from either side of the subpanel, say with epuipment racked together with no insulation from the rack, would have opposing phases this could cause ground loops or other noises?? and of course there is the common star grounding and common neutrals...oh boy I feel really out there. I can see this is not simple but is there a way you can help me get this through my thick noggin or suggest a solution??

As it is right now, to complicate matters, I'm considering going with finding a good used traditional isolation transformer, perhaps 15kva, just because of cost. If I do, what should i look for for configuration there??

I realize I'm asking a lot here so I'll try to cool my jets and see what you have to say. Thanks so much for your patience and help speedskater!
NAMASTE
vibrations1951
Posts: 40
Joined: Mon Oct 15, 2007 9:18 pm
Location: HODGDON,ME,USA

Re: isolation transformer, which one??

Post by vibrations1951 »

Speedskater/others...I've done some reading and i hope i can ask the right question.

What I need is 120V Balanced AC power with 80A capacity from my Clean power subpanel in the studio. From what I have read, i can get this through use of an isolation transformer (toroidal or standard) with 240V into the primary and the ability to get +60V and -60V out of the secondary to the panel.

What primary and secondary transformer configuration do I need to look for/request to get the Balanced AC, 120V, 80A,I want?
NAMASTE
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