Re: herbach and redman

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: herbach and redman
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 26 Nov 1997 19:01:44 -0600
Approved: tesla-at-stic-dot-net

From: 	Joshua Resnick[SMTP:seraphim-at-WPI.EDU]
Sent: 	Wednesday, November 26, 1997 8:55 AM
To: 	Tesla List
Subject: 	Re: herbach and redman



> I assume that these transformers are similar to the General Electric
> 4500
> V, 400 mA units sold by C&H Sales in CA. The weight, size, and price
> seem
> right. The third winding is nominally 600 Volts, and is used to
> connect a
> power factor correction capacitor. The transformer was designed to run
> a
> discharge lamp in a copier, so it has a lot of leakage inductance to
> limit
> the current (like a neon sign transformer). Unlike a NST at a lowly
> 400 VA
> or so, this unit is around a kVA, and having a bad power factor causes
> all
> kinds of trouble, particularly in office buildings where they use 3
> phase Y
> connected power (208/120) with a small neutral conductor. Therefore,
> they
> add the 10 uF cap to correct the inductive component. It is cheaper to
> use
> a 660VAC 10 uF cap on the tertiary winding rather than put a much
> larger
> one on the 110V primary (it would have to be about 300 uF, pretty
> expensive). 660VAC is a standard voltage for motor capacitors, etc.
>
> By the way, the presence of the tertiary winding means that you can do
> a
> cascade set up, feeding the 600 Volts from one transformer into the
> 600
> volt winding of another transformer and series connecting the
> secondaries
> to produce a 9kV, 250 mA transformer with the core of the second
> transformer floating at 4500 Volts. Two such cascades (4 total
> transformers) with the bottom ends grounded makes what is effectively
> a 250
> mA, 18 kV current limited neon sign transformer.
>
> It will weigh about 200 lbs, so you should probably do as I did, and
> mount
> it on a steel hand truck or some reasonable casters. I use mine to
> make big
> jacob's ladder type displays and to pull arcs for special effects
> purposes,
> as well as a general purpose HV power supply with a variac and a HV
> bridge
> rectifier.
>
> I haven't tried removing the shunts on these yet, but I have done
> extensive
> measurements on the leakage inductance, and other parameters. I'll
> post
> them as soon as I finish writing it up.

Can I do this setup with two transformers rather than four or should I
buy two more?
 I had thought of doing that when I realized what the tertiary  windings
were doing, but
wasn't sure that it was possible.
--->Josh<----