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oucivileng

Fri Mar 06 2009, 05:35AM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

I'm about to buy two Allanson 15kv 30ma transformers from a guy I met over the internet. He says that they're labeled "Uni-Tran." I've looked into it and it sounds a bit like a secondary ground fault protection device that they use to retrofit their old mid-point ground transformers. Please correct me if I'm wrong.

I should be able to just disconnect the capacitive detector, right? Is that going to be easy? Does anybody have any experience with this or know what I'm talking about?

here is some info about it:

Proud Mary

Fri Mar 06 2009, 06:53AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Neon Transformers
Unitran Protector Self Enclosed Style Transformer

* Recommended for indoor neon signs and indoor neon lighting.
* Outdoor non-weatherproof unitran enclosed design, providing pre-wiring for easy installation, eliminating the need for a transformer box and primary switch.
* Secondary circuit ground fault protection, interrupting transformer output to eliminate the danger of a fire in case of an arc to ground.
* Three automatic resets, eliminates nuisance tripping, provides continuous and better performance, thus saving service costs.
* A 29-minute by-pass switch, which enables efficient fault detection, in the same manner that you were accustomed to work with the old UL506 transformers.
* High power factor, 277 and 347 Volt models, which allows installation of more units on one circuit, saving material and labour costs.

Extracted from the Allanson site here:

On the about Allanson page we also learn:

UnitranÂ®, Fully integrated transformer eliminating transformer box

The phrase 'fully integrated' makes me suspect that it might be less easy to disable all the gizmos than you might have hoped.

But others may know different, and have hands-on experience of this particular model.

In the meantime, why not keep your money in your pocket till you see one of the reliable old-fashioned NSTs come up for sale?

oucivileng

Fri Mar 06 2009, 01:17PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

This is what has given me some hope: If you click the "product dimensions" link at the bottom of the page you sent me to, it looks like the secondary ground fault protection is a separate unit inside the box that could be bypassed easily. I might call Allanson but first I'll have to figure out how to get information from them because I doubt they'd be too helpful if they figured out I was trying to disable the safety device they put in because it was required by law.

Here's what the guy has:

ALLANSON - Luminous Tube Transformers - 15,000 V Type 425F Cat. No. 15B30FT UNI-TRAN Primary 120v 60 Hz 450 VA Secondary 15,000 V 30 Hz NORMAL

TRANSCO Transformers - 15,000 V Cat. No. 4B15N3-2 Serial No. 366150 T1 60 Hz W - 250 A -3.8 Primary 120 V Secondary 15,000 V Power Factor NORMAL Short Circuit Current MA 30 Secondary Mid - Pt Grounded to Case

For some reason I can't find those category numbers on either allanson or transco website. I'm assuming these are old units. I'd be picking these up myself so I doubt he's screwing with me. I assume the "W - 250" part of the Transco description refers to real power. If they have a normal power factor, are they going to be less effective for TC use? I found my old notes on power factors but I was clearly not paying much attention in class that day. I understand where the number comes from but not much else.

The reason I'd like to jump on these instead of waiting is that they're old but barely used and I don't have to mess with shipping. He's also giving me a good price.

Proud Mary

Fri Mar 06 2009, 02:07PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

If I was in your position, my worry would be that the supplementary circuitry might be embedded in a monolithic epoxy block, but others on the forum may be able to advise you a lot better than my guesswork.

oucivileng

Fri Mar 06 2009, 02:35PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

Are the Transco transformers worth going after? I'm looking at different models on the Allanson website just for reference (they have an easier search page) and I'm seeing a couple of 15kV/30mA NST's that say VA=250. Isn't VA just supposed to be V*I ?! I'm clearly missing some key piece of information here.

ConKbot of Doom

Fri Mar 06 2009, 03:14PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

"Hi I have this transformer, and its having issues with the fault protection circuitry, can it be sent in to be repaired or is it potted in so the whole transformer has to be replaced?"

They could still avoid giving the answer you want, but I would imagine that would work decently well.

Proud Mary

Fri Mar 06 2009, 03:51PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

oucivileng wrote ...

I'm seeing a couple of 15kV/30mA NST's that say VA=250. Isn't VA just supposed to be V*I ?! I'm clearly missing some key piece of information here.

Yes, you are!

It's easy to imagine a situation in which there is both voltage and current, but where no work (watts) is actually done. Consider the case of a pure capacitor tied across the output of your transformer - the current through it might be quite high, and your transformer might be getting quite hot, even though no work is actually being done i.e. there is no power.

This seeming mismatch between I x A, and Volt-Amperes is called the Power Factor. (Google for this basic!

) A power factor of 1 means that there are no losses due to capacitance or inductance, while a power factor of nil means the exact opposite - that there is both voltage and current but no power.

This is why transformers are generally rated in Volt-Amperes - VA.

Proud Mary

Fri Mar 06 2009, 03:55PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Posted in error by Harry.

Dr. Dark Current

Fri Mar 06 2009, 04:06PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

oucivileng wrote ...

I'm seeing a couple of 15kV/30mA NST's that say VA=250. Isn't VA just supposed to be V*I ?! I'm clearly missing some key piece of information here.

It could have integrated PFC cap

Proud Mary

Fri Mar 06 2009, 04:19PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

A fellow here has modified an Allanson 12000V, 30mA Unitran NST , so perhaps it is less difficult than I feared:

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