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Re: Freau's efficiency theory=Success!
Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>
Tesla list wrote:
> Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> Hi John, all,
> > I thought that adding PFC would stop the NST's (over-current) suffering.
> I believe this is not the case.
> A PFC capacitor connected across the primary of an NST draws a reactive
> current from the supply which is 180 degrees out of phase with the
> reactive part of the NST current. The supply current is the sum of these
> two currents. So the inductive part of the NST current is cancelled by
> the capacitive current drawn by the PFC.
> This reduces the overall current drawn from the supply line, but the
> windings of the NST still see the same total current with or without
> PFC. It is only the line current which is reduced by cancelling the
> reactive contribution. However, PFC is still worthwhile as reduced line
> current makes life easier for the Variac, circuit breakers and wiring.
> This is one of the reasons why I believe that larger systems should be
> designed with high PF in mind from the outset. A poor power factor in
> a large system burdens the transformer and ballast, and requires a lot of
> PFC capacitance to make a significant improvement in the power factor.
When the transformer secondary is loaded with a capacitor and spark
gap, how do you figure the amount of inductive reactance to cancel?