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Re: [TCML] Solid state efficiency, was: mini Tesla coil specs]



So almost immediately...a follow-up: Belatedly I thought to resonate the primary & try it again. This time, a) the current's a sine-wave all the way; but b) switching /starts out /near current/ /z.c/./ and after about 4 cycles it's shifted to current-peaks, where it stays. The current is, of course, a lot greater due to the series-resonance, causing the secondary's output to rise faster.

But a) where's the advantage, if switching drifts toward current-peak. And b) how to handle the greater current? (Bigger hardware, that's how!)

And finally: Whichever way one goes, it seems as if one will have to put up with switching near current-peaks--unless one can produce the spark within the 1st 4 cycles or so in a DR design. I haven't simulated that yet.

Comments?

KCH

-------- Original Message --------
Subject: 	Re: [TCML] Solid state efficiency, was: mini Tesla coil specs
Date: 	Sun, 15 Nov 2009 13:19:09 -0800
From: 	Ken or Doris Herrick <kchdlh@xxxxxxxxx>
To: 	Tesla Coil Mailing List <tesla@xxxxxxxxxx>
References: <cc2218e80911111413md7c0b57k355ad83baa7e78a4@xxxxxxxxxxxxxx> <4AFC3E64.90209@xxxxxxxxx> <cc2218e80911130718k750de578t197b1d7d7677aaa9@xxxxxxxxxxxxxx> <4AFDCA69.4090001@xxxxxxxxx>



From KCH-

While I have the attention of a few s.s.'ers here, perhaps someone can shed light on this: I'm simulating what amounts to a half-bridge driving an untuned-primary t.c. I record waveforms of a) MOSFET current and b) primary current. I notice the following: At the start, the MOSFETs switch at current peaks and the current waveform is triangular. As the primary current--and secondary voltage, of course--builds up, the current waveform gradually changes toward a sine shape and the switching events shift toward current-zero-crossing. I have a feeling that that's the case in the real world. Is that to be expected?

KCH


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