RE: [TCML] SISG heating at high freqencies [SEC=UNCLASSIFIED]

["Jason Judd" <JJudd@xxxxxxxxxxxxxxxx>]

Hi Peter, sounds to me like your primary is ringing for many cycles
which would happen if the power going in is not being removed rapidly
like the secondary would normaly do. If you are just playing around and
haven't really tuned the system, doing so should result in much less
heating.

Jason.

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Peter Terren
> Sent: Thursday, 17 April 2008 7:29 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] SISG heating at high freqencies
> 
> I was playing with a 4 segment SISG with a 4 inch coil about
> 8 inches tall and 0.06 uF cap.
> Primary of 2 turns from a ballasted MOT (half wave rectified) and no 
> toroid.
> Frequency would have been quite high >2-300kHz or even more.
> I was just messing around with the threshold voltages for curiosity 
> and was using 3 of the 4 segments to get 1 inch sparks.
> 
> I was quite surprised to find that the SIDAC's were scorching hot and 
> the IGBT's were uncomfortably hot, particularly one of them after a 
> very short run.  Considering that these have been used by others on a 
> pole pig with only mild heating, that surprised me.
> It sounds like they had some frequency dependent problem because the 
> SISG works OK (ie cold) with more primary inductance/capacitance.
> Beats me why the SIDAC's were getting hot though. Perhaps the IGBT's 
> weren't turning on fast or fully so the SIDAC's spend more of the time

> conducting throughout the cycle relatively. Perhaps a lower gate 
> resistor may have helped (I was using 100 ohms).
> I was planning to use a smaller 4 stage SISG for a demo mini coil but 
> would have to sort out the frequency issues first.
> 
> Peter
> www.tesladownunder.com
> 
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