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Re: Recent s.s.t.c work



Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

For the record, a photo of the present state of work, <http://hot-streamer.com/temp/KCH_TCH3.jpg>http://hot-streamer.com/temp/KCH_TCH3.jpg. Ref. also -KCH_TCH1 & -2.

Per Steve Conner's comment & my belated realization, I've relocated my toroidal current-transformer to one end of the primary LC--the capacitor end, as most convenient. It's inside the bucket at top center & has100 turns. The blue/white twisted pair will lead from that to the 2nd, 1:1, transformer on the l.v. circuit board.

I've cut the copper sheet-stock connection between the pairs of electrolytic capacitors and installed a 100 mV/50 A current shunt, visible at the center of the image. That's for monitoring IGBT common-mode current if any (and negligible, I hope!). It's electrically at mains-common so differential probes should not see too much common-mode voltage to scope-ground.

I have installed the replacement pair of (used) IGBT bricks, recently received, & have added, for their protection, 2 uF/800 V capacitors across the electrolytics (just visible behind & below the current shunt) and strings of breakover diodes directly across the bricks, visible above the copper-braid interconnecting straps.

The "-"-side current shunt for sensing over-current remains the same, at the upper left.

I've modified the circuits on the l.v. board and what remains now is to put that board back in place & re-start the debugging procedures, paying more attention this time to common-mode current and proper feedback operation. I'll start out with no h.v., no connections to the IGBTs and substitution from a sig-gen of the feedback signal from the 100T toroid, hoping to get most of the l.v. circuits operating as designed prior to connecting up the IGBTs.

But first, likely a spot of loafing. I've found that, in retirement, I tend to loaf more and work less.

KCH