RE: [TCML] Re: Hot Primary

["Lau, Gary" <Gary.Lau@xxxxxx>]

The observation that inner primary turns get hotter than outer ones is not just on DRSSTC's.  My 15/60 powered coil and no doubt many others exhibits this as well.

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Steve Ward
> Sent: Tuesday, February 23, 2010 12:18 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Re: Hot Primary
> 
> Hi Greg
> 
> On Mon, Feb 22, 2010 at 9:56 PM, Greg Leyh <lod@xxxxxxxxxxx> wrote:
> 
> >
> > I'm unfamiliar with the particulars of your primary drive circuit, but it
> > seems to me that there shouldn't be *any* noticeable heating of the copper
> > at all, otherwise the unloaded Q of the primary will be very low.
> >
> 
> Hopefully we can increase your familiarity ;-).  The DRSSTC has the capacity
> of running much longer drive periods, whereas transient excited systems are
> limited by losses and coupling coefficients.  The capacity for running many
> cycles of RF per spark event, allows the operator to really drive up the
> primary RMS current to huge levels because the duty cycle can be
> significantly higher.  But back to numbers... the Q for this system is
> easily more than 10, as im betting his primary voltage is about 10X the
> H-bridge output voltage when he hits 3kA, and with no secondary in place im
> guessing the primary envelope is a fairly straight ramp, meaning the Q is
> likely in the 30-60 range at least.  Perhaps if Dave has a DSO he could
> capture his primary current shape (with no secondary in place) ramping up to
> 3kA.  It would be important to capture the bus voltage as well (because bus
> voltage sag would make the primary current ramp taper off, artificially
> looking like lower Q).  From there we could determine the actual Rac of the
> primary, at least to some degree of certainty based on how good the data is.
> 
> I like the idea of this method, since it allows for convenient and safe
> measurement of purely resistive loss.  I might give that a try on some of my
> systems.
> 
> Steve

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