[Prev][Next][Index][Thread]
Re: Power Transformers
>>From bert.hickman-at-aquila-dot-comMon Nov 11 22:11:06 1996
>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
Bert wrote:
<snip>
>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 think I'd be looking for these too. Good score Bert!
>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...
>Safe coilin' to ya!
>-- Bert --
Bert, All,
My only limited experience with installing shunt resistance across
the primary control/limiting reactance has been that when the
resistance was added, the power drawn from the mains was reduced, and
the system performance went for a crap.
I use a good commercial line RFI filter between my coil primary power
circuit and the rest of the planet. Since I have employed this filter, and a serious
grounding and screening system in the firing room at my old lab
location, I stopped blowing up 'stuff' upstream on the mains. Don't
misunderstand me. I have blown up lotsa 'stuff' upstream on the mains
during my 'learning curve'.
I haven't had a chance to 'scope' the goings on in the primary
circuit except briefly once. I agree with you that some extreme spikes can be
created. I wouldn't be suprised if these surges aren't working for me in a
positive way in my very successful MTC system where I employ 10
millihenries of primary control reactance without resistive bypass damping,
and have silky smooth variac control with no power bumping
whatsoever. Note that I also employ 240 mH series inductance out of
the secondary of the power transformer on this unit.
I do know that the extra, series secondary inductance causes huge decrement
waves every time the break closes, which are impressed on the transformer
secondary. This circuit is a wild place. I hope to scope the total
goings-on soon but in the meantime, all I know for sure is that my
synergistic arrangement works like gangbusters, even though I cannot
tell you why at this time.
My point is that your advice to employ damping resistance across the
control reactor does not ALWAYS work best.
rwstephens