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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Hi Steve
I found that my first attempt at a gate driver floated its output high in the same way. I think I documented that and the fix I used for it back over on the old board.
The more I think about it, the more I agree that 1/4" pipe is too wimpy. The pipe I have is slightly smaller than 1/4" in fact. I probably ought to start over with a bigger resonator too. But I'll probably go with it for testing, it should hold up for short runs.
It's good to know I was right in suspecting that I could leave the film decoupling caps out, too
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Update:
I'm real busy with work, and my band is in the middle of recording an EP, so Odin has got kind of neglected lately. I will finish it though! I've wound all the isolating transformers and bought the Cat5 sockets. I decided to make a new primary from 3/8" copper pipe, cable ties, and the lid of an Ikea plastic laundry basket, so I need to go and do some shopping.
I also decided to order another batch of PLL boards, since I screwed up and couldn't supply them to everyone who wanted them.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Ikea laundry basket sourced! Nothing else to report except the record is getting mixed this weekend and then I can concentrate on the coil
I apologize to anyone that I said I would sell electronics to and then kept waiting. I've just ended up being way too busy with other stuff. I really want to get Odin finished and demonstrate that he works before I go selling the isolated gate drive system. I don't want to sell stuff unless I'm 100% sure that it's good. Well 95% maybe
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Update: I had to wander off and do a load of other stuff that pinched all my evenings and weekends, but I'm now back on this project! I spent ages designing it, and this year would be Tesla's 150th birthday, so it's got to be done.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi steve
Well some good news.. there weren't DRSSTC's around for a while, I can't wait to see more progress!
Just regarding the HI-pot test, I would be a bit vary about those little transformers, if you plan hooking them up to a MOT!
Actually, I don't trust transformers wound with just enamelled wire even for low voltages, after I had some of them get their lacquer damaged and short out... You'l have 800 volts across your transformers!
Now I paranoidly use PVC insulated wires and I didn't regret that yet... CAT5, screened, various tiny coax and similar cables are also handy, but that's amtter of opinion I guess!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
You are right. If they're going to short out, I don't want to have the cap bank discharge through them and destroy the whole driver. So I need to test them to make sure they can stand the voltage plus a big safety margin. Hence, a MOT on a variac putting out, say, 1600V peak
If it does turn out to be a problem, I can rewind them with kynar wire-wrap wire or such like.
The primary and secondary windings are separated on opposite sides of the core, and I believe ferrite is an insulator (sort of)
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Regarding ferrite, I managed to make it arc over at several hundred volts to kilovolt or so. It probes as and insulator, but actually conducts HV pretty well once it ''breaks down'' at some point.
Real danger is, actually, not only blowing your driver but also blowing your IGBT gates, IIRC.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I second that enamel wire sucks for GDT use, since its highly probable that the person winding it will end up scraping off some enamel when it rubs against the ferrite (which by the way, is an OK conductor, definately not an insulator!). Ive had my mag-wire GDTs fail in SSTC service with a plume of smoke and a shattered ferrite!
On my DRSSTC 2 im using cat-5 wire, which i tested with a 9kV NST for hours (its good stuff at 60hz). The NST failed before the twisted pair of cat 5 did!! Of course, this was a perfect, new piece of wire, no nicks in the insulation or any of that.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Oh well, you guys were right. All four driver boards failed the hi-pot test completely, the transformers sizzled and went up in smoke at about 500V. Back to the drawing board, I guess
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