Re: what is "power factor rating?"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Date: 04 January 2001 14:56
Subject: what is "power factor rating?"

Hi Joseph!


>Original poster: "joseph gallo by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <juzeppy-at-hotmail-dot-com>
>


<snip>

>anyway what is the Power Factor Rating and why would I need
a power
>correction capacitor?(I didn't need one on my other coils)
>
>can anyone explain
>Joseph


Well I'll try.  As to **need** power factor correction,
depending on how big the power supply, you may or you may
not, but for an OBIT of 10kV 23mA = 230VA I doubt it'll make
a lot of difference - if it was a pole pig and you were
running 10kVA you possibly would notice the difference.

As to what it is . . . it's down to phase differences.  In a
resistive load, like a tungsten filament light bulb, the
volts and amps are in phase.  If the load is reactive (a
capacitor being charged for instance, as in the primary
circuit of your coils) the volts and amps are out of phase.
This results in more power being taken from the mains supply
than is actually used (the excess is called "wattless power"
because it doesn't do any work, and recognition of the fact
that the volts and amps may be out of phase in a load on ac
is the reason why the power ratings of transformers are
referred to in VA and not in watts) and to set this straight
means doing something about the phase difference.  You now
know what that something is - properly-rated capacitors
designed for power factor correction (and *not* any old
capacitors) are simply connected across the mains supply
before the transformer.  If the right value is used the
volts and amps are in phase again at the wall socket and
there is no wattless power taken from the supply.  This
matters to the supply company because large reactive loads
would be a nightmare for them, and it matters to you because
electricity meters still measure wattless power and you get
billed for it, moreover it can still blow fuses and trip
breakers.  If your coil is only a few hundred VA, you're not
likely to notice, if you run a few kVA you might well.

As to whether power factor correction makes a difference on
spark performance yet again I wouldn't think so on small
coils, but might on big ones, if only by preventing the
breakers tripping, though I really can't comment on that as
I have never built a big 'un.  Maybe someone else on the
list who has built big coils can.

Dunckx