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Re: Chaotic Resonance(Solid State Coilers)



Original poster: "Charles Hobson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <charles.a.hobson-at-btinternet-dot-com>

Hello all,

There has been a lot of traffic on "Chaotic" so here's my contribution:

I recently did a series of measurements and calculations on a Boiler
Ignition Transformer  (8.3kV/20mA)  to determine, amongst other things,
what value capacitor will resonate with the secondary winding. Because 240V
mains and 8.3kV are not friendly, I fed 18V to the primary winding instead
and measured 630V output, a predictable result. I then applied various loads
to the transformer and measured and recorded primary and secondary voltages
and currents.

Under these conditions, the transformer secondary took a fancy to a
 0.0047uF (4.7nF) capacitor. That's where it resonated at 50Hz. The output
voltage sky rocketed to 4000V. Now here is where some software may get its
knickers in a twist:

a. formula for transformer voltage and turns ratio not applicable to
reactive loads
b. VA in secondary =23.6, VA in primary = 1.98  at resonance

Where do all those Volt Amperes in the secondary come from? Do we have a
free lunch here?  No! definitely not. The computer tends to look at a steady
state conditions and make calculations accordingly. Some software may even
tell you that there is a Power Gain in a linear non-active circuit. Most
software I think can recognize true power, apparent power, and reactive
power differences, but resonance poses some problems.

What is actually happening is the secondary circuit under resonance is
ringing. Energy is moving back and forth between the capacitor and
transformer inductance. much like a pendulum or child on a swing is moving
up and down from one side to the other. The small amount of energy being
consumed by I square losses R in the transformer is all that is needed to
keep it going, like that small nudge on the swing to keep it going. How did
the swing get started? The struggle to lift the swing from rest to a release
point. The transformer's initial energy was supplied as a transient when
first connected. (the large surge of current at switch on). The product of
this and 18 Volts integrated over the short time of occurrence represents
this initial energy.  Mystery of the great joule robbery solved.

Chuck    .