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Re: PFC for Neons
Hi John and all,
The contradictory statements I noted were the two I
marked with asterisks in my original reply.
>> Note that power factor correction is normally used to reduce your
>> electric power bill. (******)
<snip>
>> A higher power factor means less current from the utility but the
>> current saved is reactive current which does not affect the meter.
>> (******)
<snip>
> You mentioned possible resonance problems in the pole pig
> secondary/Tesla primary system. I would be interested in how to
> calculate the conditions so the problems could be avoided.
There were a couple of discussions on this several months ago.
Any impedance strung on the polepig primary is transformed by the
turns ratio squared to appear in the pig secondary. There was a
discussion on "bumping" when the variac (I think) was cranked above
40% whereby the system jumped into 60Hz resonance. Perhaps those
using pig systems could elaborate. In my case, I found the high
secondary inductance of the neon (around 60H for the 12kV 60mA
unit) was resonating at a frequency depending on the value
of the primary cap.
In all cases, problems are alleviated by the use of damping
resistance to reduce or kill this. I used several kilohms in the neon
secondary circuit.
One thing is to avoid setting the gap too wide to prevent
overvolting the secondary. For async. rotary expts. with the neon I am
going to shunt the rotary with a fixed gap to catch any misfires.
Unfortunately, the resistance is still necessary as the resonant
condition causes the currents in the neon secondary to exceed greatly
what it can supply into a resistive load. This is probably why so
many of these units die in Tesla service.
For a pig system, it is common practice as far as I know to use
oven elements etc. in series or parallel with the limiting inductance
on the primary side. You can't do this with a neon as the shunted
magnetic circuit effectively isolates pri and sec (not an ideal
transformer).
Malcolm