Re: Chaotic Resonance(Solid State Coilers)

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

Hi Pete,

You wrote:
Original poster: "Peter Lawrence by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <Peter.Lawrence-at-Eng.Sun-dot-com>

I find this interesting because my back-of-the-envelope calculation using
the traditional resonance-capacitor formula yielded a different value.

1 / (2 * PI * 8,300/0.020 * 50) = 7.6nF

I wonder what's wrong here. Did you try a capacitor value near 7.6?

-Pete Lawrence.

Thank you for pointing this discrepancy out Pete. Your back of the envelope
calculation is spot on for an 8.3kV 20mA transformer. 7.6nF is the size
capacitor which  resonates with the transformer secondary winding.  My
particular transformer actually measured 18mA rather than 20mA short circuit
secondary current, when powered at its specified primary input voltage (240V
50Hz) Had you known this you would have got  6.9nF. My apologies for this
small error in tranny specs.

I have a web page at my web site which goes into some details on such
transformers for what it's worth. It will also confirm your "back of
envelope" method.

www.charles.a.hobson.btinternet.co.uk/TRANSFORMER_ANALYSYS.htm


So, "what's wrong here"?. The transformer was operated at 18V input rather
than its rated 240V. and gave results inconsistent with 240V operation.
This particular unit  didn't seem to behave linearly. For example: its
primary winding inductance appeared as 5.7H at 18.2V input  and 11H at 240V
input.  (Secondary without load)
(Method: measured primary currents at 18.2V (10.2mA) and 238V (66mA),
assumed impedance V/I to be reactive only (XL>>Rp) and calculated the
inductance in Henries)

More relevant to traditional methods, At 18.2V input the output was 630V.
The secondary short circuit current measured 0.9mA. XL = 630/0.0009A = 700k.
Again XL >> RS in the transformer secondary winding so  C worked out to
4.5nF
At 240V input short circuit secondary current measured
at 18mA. XL=8.3kV/0.018A = 461k. C works out to 6.9nF. Like you, I have to
suppose the BIT and NST secondary current specification is actually the
secondary short circuit current. I can't see any other practical way to
specify them, can you?
:
Perhaps there is good explanation for what is happens at different voltage
inputs: making incorrect assumptions, ignoring relative magnetising currents
and hysteresis losses, etc.??  .

Best regards   Chuck