Hi David.
It sounds similar to the designs used in microwave ovens that has been
discussed several times on these groups where a matgnetic shunt is
placed so that the primary flux has an alternate path from the
secondary. Leaking a limited amount of flux into the secondary would
give the symptome you describe where the transformer also acts as a
ballast and would be useful to run an arc lamp.
Your observation of the name would also seem to be correct.
The only thing that doesn't fit is the current rating but possibly it
refered to the primary current.
---
Ron
"Dr. David Kirkby" wrote:
>
> With all the questions about transformers on here, I thought I'd add this and
> would be interested in comments.
>
> About 10 years ago, a friend was building a twin 4CX1000A amplifier. A company
> (which I believe was involved in printing) near where I worked went bust. As
> their offices were being cleared, I found in the skip a large piece of
> equipment
> with a transformer marked 'Prime-Arc 2600 V 3.15 A'. This looked an ideal
> transformer for the amplifier, so with the help of someone else, I removed the
> transformer and got it home. I can't recall the exact size, but it was
> probably
> about 10" x 10" x 10".
>
> Power was applied to the 240V primary and the secondary voltage was about 2.8
> kV
> or so (can't recall exactly), but it seemed reasonable for a 2.6 kV
> transformer.
>
> A box was welded to house the power supply and all seemed okay. There was
> something over 3 kV off load (again I can't recall the exact values). All
> seemed
> okay, until we tried to use it. At that point we discovered that the short
> circuit current of this transformer was about 20 mA, despite the fact the
> plate
> on it said it was a 2.6 kV 3.15 A transformer. It seemed quite happy to run
> into
> a short, without getting hot or blowing our fuses.
>
> One might have concluded the transformer had a fault. However, when we tried
> to
> get a transformer wound, with a similar voltage at 2.6 A (less than the 3.15 A
> of this transformer), it became apparent that nobody could make a transformer
> of
> that rating that would fit in the box we had made. Hence a new power supply
> box
> was welded up, to take the larger transformer we had wound.
>
> So why did a physically large transformer, with a rating plate of 2.6 kV at
> 3.15
> A, have a short circuit current of about 20 mA ? It seems unlikely it was
> faulty, since a transformer of lower spec could not be made quite as small.
> The
> fact the equipment I found this in was disposed of when a company went bust,
> rather than thrown out since it was not working, again makes me think the
> transformer had not developed a fault.
>
> The equipment could well have had some form of arc lamp in it, so perhaps that
> is where the name 'Prime-Arc' came from.
>
> The transformer has long since been thrown away, so I can't measure
> resistances
> of it. However, it was a very expensive mistake in terms of time welding up
> power supply boxes and mounting all the components, only to discover the
> transformer was useless.
> --
> Dr. David Kirkby PhD,
> email: drkirkby@ntlworld.com
> web page: http://www.david-kirkby.co.uk
> Amateur radio callsign: G8WRB
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
|