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Current Limiting


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From:  D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent:  Friday, January 30, 1998 6:41 PM
To:  Tesla List
Subject:  Re: Current Limiting

to: Mike & Ed

We use a 12 ft. long coilwound resistive element with a 0.6 Ohm value in
series with our normal inductive reactance.  This small resistance has the
effect of smoothing the peak current flows during times of near or actual
core saturation.  The peak loads on a typical 5-6 kva unit hits nearly 10
times that value during initial cap recharging.  The primary culprit here
is the very low impedance value of pole xmfrs and potential xmfrs.  This
resistor makes a considerable difference in the relative "smoothness" of
operation of both the output spark and the RSG operation.  You can hear the
difference in a running system with and without the resistance element.

DR.RESONANCE-at-next-wave-dot-net


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> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Current Limiting
> Date: Friday, January 30, 1998 3:54 PM
> 
> 
> ----------
> From:  Esondrmn-at-aol-dot-com [SMTP:Esondrmn-at-aol-dot-com]
> Sent:  Friday, January 30, 1998 1:08 PM
> To:  tesla-at-pupman-dot-com
> Subject:  Re: Current Limiting
> 
> In a message dated 98-01-30 00:59:54 EST, you write:
> 
> << 
>  I was thinking this morning about current limiting.. [I still dream of 
>  the day I can get that Pig... and want to be ready] I thought of
>  something that is a) very simple, and b) probably does not work.
>  So someone tell me why please :)
>  Since I am mostly a software kinda guy, with a smattering of digital
>  design, dealing with this high-power AC stuff always confuses me.
>  
>  If I understand it correctly - the idea behind reactive or resistive
>  loads is to place an IR drop in series with the pig, such that when
>  the current reaches a certain point, the IR loss prevents it from
>  rising further [I know, the wording sucks, but the idea is 
>  clear, I hope]
>  So.. based on this idea.. and the fact that lightbulbs don't exactly
>  short things out, why not use lightbulbs as resistive ballast?
>  I am not exactly sure what the VA rating for a bulb is.. but for
>  grins sake, assume a 100W bulb is 100VA, paralleling 2 bulbs gives
>  you total power flow of 200VA, 3.. etc. [ for 220, use 2 110V bulbs in 
>  series]. 
>  
>  Power control is two fold: Voltage via variac, and current by switching
>  in more or less bulbs in series. 
>   >>
> - snip -
> 
> Michael,
> 
> Your approach will certainly work as well as using heater cores, oven
elements
> and other resistive elements.  However, it is not an ideal solution. 
Resitive
> ballast will drop quite a bit of voltage across it and lower the voltage
> available to the primary of the HV transformer.  Using reactive ballast
such
> as a variable inductor will also drop some voltage across it because if
its
> internal resistance but not nearly as much as a resistive ballast.
> 
> Ed Sonderman
>