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Re: Winding primaries



HI all,

> Original Poster: Kennan C Herrick <kcha1-at-juno-dot-com> 
> 
> >From Ken Herrick:  
> 
> You might try a simple type of test that I recently did:  Requires a
> 2-channel oscilloscope and a signal generator.  Connect one scope probe
> to your secondary and connect the generator to an appropriately-shaped
> loop of wire simulating your primary.  Use several loops if you have
> several primary configurations in mind, all having the same quantity of
> turns.  You may need a series resistance of a few hundred ohms at the
> output of the generator to avoid loading it down unduly with just the few
> turns of wire.  Connect the other probe across the wire loop (at the
> loop-end of the resistor, if any).
> 
> Next, position the loop at the appropriate place with respect to the
> secondary & tune the generator to the secondary's resonant frequency. 
> Record the amplitudes of the loop's voltage and the secondary's voltage. 
> Then connect the next loop and do the same thing, adjusting the
> generator's output voltage as required to keep the loop voltage the same
> as before.  
> 
> That way, you can see the relative efficiencies of the various modes of
> coupling a primary to the secondary.  Although I employ an essentially
> flat primary (of 1 equivalent turn, as it happens) in my t.c., directly
> under the secondary, I've found that significantly better coupling ensues
> with a primary positioned about 6" up (out of 35" or so).  I don't use
> that better positioning, though, in order to keep the primary away from
> the strong electric field, so as to protect my MOSFETs (but I'm working
> on how to ameliorate that electric-field problem).
> 
> Regards-  KCH

I'd just like to note that connecting scope probes directly to the 
secondary will affect its Q (and hence an attempt to derive transfer 
efficiency) severely. Better to pick up the e-field from a distance.

Regards,
Malcolm