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Re: PFC Question
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- Subject: Re: PFC Question
- From: "Tesla list" <tesla@xxxxxxxxxx>
- Date: Fri, 11 Nov 2005 06:29:32 -0700
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Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
It has often been said that the inductance of the variac (that
changes with setting) causes the phase of the charging waveform to
change with setting. I have personally experienced this phase change
with variac setting and assume that it is due to the variac
inductance vs setting. What is needed here is to measure the phase
of the variac output wrt the phase of the input of the variac to put
things into perspective. Your estimate of 1mh of leakage inductance
is based on a coupling of 0.99. This coupling seems high to me. If
the coupling is say 0.95, the leakage inductance may be significant
enough to cause the output phase shift. I have disassembled a variac
of old design and found the the area of actual core to be much less
than the area of the winding. It would not surprise me to find the
coupling to be less than 0.99.
Another theory that may explain the phase shift vs variac setting is
the non linarity of the NST (my experience is with NST's). As the
variac output is increased, the NST may be going into saturation that
may effectively decrease the current limiting inductance. This could
also cause a phase shift in the charging waveform as the variac
output is changed.
Dont know the actual truth, but there is a phase dependency of
charging waveform phase vs the variac setting. This dependency
requires the SRSG to be re-adjusted as the variac output is increased.
Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>
> Original poster: Steve Conner <steve@xxxxxxxxxxxx>
> I was also surprised to read that. Say you want to
> draw 30A at 240V, the ballast reactance is going to be
> on the order of 5 ohms which is 26mH in a 60Hz system.
> 1mH is negligible compared to that.
any comments on this, Jerry?
> But, imagine you're using an ungapped variac as the
i can`t imagine _i_ do that - it`s just too st##id for me :-D
Neon transformers are doomed in Tesla service! I should know, I've
killed more of 'em than many pople have ever even seen in a life time.
25-03-96 (c) Richard Hull, TCBOR