RE: OLTC update - primary IGBT loss

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Gary,

There are two factors at work here.

First, I am trying to make the thing really efficient so I am fretting
about power losses.  I suppose I could just dump a whole lot more power
into it but then the over all efficiency might be "only" as good as a
typical coil. ;-)

Second, the voltage gain is really high  SQRT (0.492/404e-9) = 1103!!  The
gain of my big coil is only SQRT(0.075/132e-6) = 24.  Max voltage for each is:

1103 * 560 = 617680
24 * 21000 = 504000

That seems about right from that point of view...

It may be that I was trying way to hard for voltage gain and I over did it
at the expense of current to drive the streamer.  I may have way too high
of output impedance.  I am studying all this now so I don't have the answer
yet.  However, I suspect going to a much larger toroid and pulling turns
off the secondary (low voltage and higher current) would be a good thing
(but taking wire off is a whole lot easier than trying to put it back on
;-)).  The Q's are sort of low, but they alone should not be a critical
problem.  If the output impedance is way off, that is a big problem that
only amplifies the Q losses.  We don't normally worry much about this stuff
because it is messy and we just hope it's ok.  I seem to have found a case
where it is all very important!

Much to ponder...

Cheers,

	Terry


At 11:48 AM 9/3/2002 -0400, you wrote:
>Hi Terry:
>
>While primary circuit Q has always been viewed as important, I recall many 
>considered opinions suggesting that secondary Q was not so critical.  
>Suggestions were made to wind secondaries with Litz wire, and the prevailing 
>response was that secondary losses (in disruptive coils) were not worth 
>fretting over.  Please help me to reconcile this with your secondary 
>situation.  Is your secondary just outrageously more lossy than a typical 
>secondary coil?
>
>Thanks, Gary Lau
>MA, USA
>
>