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Re: THOR PROJECT: SUCCESS!!!
Hi Marco,
You never told us what spark lengths were under these
conditions. Pretty please?
Regards :)
Malcolm
> Original Poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi>
>
> Hello all.
>
> After the last power supply breakdown I talked to a guy from Intersil: he
told
> me that if the IGBTs fail with gate, collector and emitter shorted it is
likely
> a gate-emitter overvoltage condition causing of the failure.
>
> Therefore, I decreased the IGBT drive voltage from 17V to 15V, added a fast
> over-current protection limiting the IGBT current to 33A and added also a
> couple
> of decoupling capacitors on the controller board (the one generating the
drive
> pulses to the IGBT bridges).
>
> As the design is modular (two 5kV modules at the moment) it also took a
second
> to wire it to give +/- 5 kV referred to ground, instead of +10 kV referred to
> ground. I had thus a simmetrical power supply. That halves the HV stress
on the
> power supply transformers.
>
> Result: this morning I had several 30 second runs with the power supply
> connected to my old TC.
>
> IT WORKED FINE! The power supply was NOT damaged! Long, steady ramificating
> streamers!
>
> Pulse voltage was 11 kV DC, repetitions rate was about 660 Hz: that makes a
> power of about 2kW (with the 0.05 uF cap I had).
>
> I also measured all with a scope and printed a few snapshots: In a few days
> I'll
> scan them and put them on the web.
>
> Next step: modify the PROBE board to measure two voltages (positive to ground
> and negative to ground), sum them and also subtract them. The sum will be the
> net output voltage measurement, the difference will be an alarm signal
warning
> if the positive and negative outputs difference crosses a safety
threshold (if
> the two module outputs get too much unbalanced).
>
> That will include also embedding the HV divider networks into epoxy and a new
> PCB layout design for the PROBE board: maybe another month all together.
>
> Regards
>
>
>
>