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Re: Power Transformers

Tesla List wrote:
> 
> >From jim.fosse-at-bdt-dot-comTue Nov 12 22:45:27 1996
> Date: Wed, 13 Nov 1996 05:27:07 GMT
> From: Jim Fosse <jim.fosse-at-bdt-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Power Transformers
> 
> >Date: Sun, 10 Nov 1996 22:45:37 -0800
> >From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Power Transformers
> >
> [snip to save chip]
> >
> >In order to keep the size and cost down, the ballast inductor should use
> >some type of laminated iron core.
> Good post Bert,
> > Wire size should be
> >large enough to keep I^2R losses manageable - #6 or #8 AWG will be good
> >up to 50 Amps for intermittent duty. The solenoid could be wound from a
> >pair of #10 AWG wires in parallel to achieve about the same ampacity.
> >
> I'm using dual #19 on a 3" pvc former filled with "Is" from some old
> transformers I had wound years age.  It works well (-at-20A) for a few
> tens of seconds before the IR losses heat it to the point where the
> PVC former starts to smell;)
> 
> > Other alternatives include ballast inductors for high-power arc
> >mercury or sodium vapor lighting, or even some types of microwave
> >transformers with the secondaries shorted.
> 
> also shorted Neon sign transformers.

Hmm... Great idea! I'd just been pitching mine when I blew them out!
> 
> > Large arc-lighting ballast
> >inductors can often be found at scrapyards for $10-20 (since they have a
> >fair amount of copper and iron). I just purchased one at the local yard
> >that handles 6.5 KVA and weighs 52 pounds for about $20.
> >
> I've got 2 small ones that limit at about 10A each with their
> secondaries shorted. Mine are 1 KVA autotransformers with current
> limiting shunts between their primary and secondary.

Yeah, the yard had 2 big barrels full of various types of shunted
autotransformers and simple reactors. The BIG ones were apparently for
3-phase, with 3 separate reactors, EACH being probably 200+ pounds. Knew
the wife would kill me, so I settled for a smaller one! Played hooky on
my birthday and went to the junkyard! Neat place to visit! My wife's
still shakin' her head...! 
> 
> >Note that high-power shunting resistors are essential to keep voltage
> >transients down to a manageble level when the gap is quenched. These can
> >be space-heaters, hot-water heater elements, or oven elements, but must
> >be capable of safely dissipating up to several kilowatts of heat. Not
> >using these can mean that inductive kickbacks will get back into your
> >power mains and wipe out your computer, VCR, answering machine, etc...
> >
> Also include a "PFC" cap between you ballast and any RFI filters that
> you use, otherwise the inductive kickback will blow the common mode
> caps in the RFI filter AND any unhardened electronics connected to
> your power mains. ( I've blown 2 light timers just doing ballast
> experiments;(
> 
>         jim

Oh yeah, I did forget to mention the PFC's. Couldn't hurt, and they'll
improve the overall power factor of the system to boot. These should be
rated for at least 600 volts or better on the 240V Mains. I'm going to
use a batch of 35uF -at-2000 Volt jobs I picked up for cheap at a Hamfest
this fall. Now that I'm beginning to play around with PSPICE, I want to
do some more experimenting with the ballast and coil model you created
earlier this year...

Safe coilin to ya, Jim!

-- Bert --