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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