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Registered Member #154
Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260
Hi tom,
Thanks for the suggestion, I will try the split tank cap arrangement, i think Steve Ward used to do that on his early ISSTC coils too. I do use TVS across each IGBT collector to emitter, How many TVS do you use on your string from MMC to ground?
Banned on 3/17/2009. Registered Member #487
Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617
Yes Thats how I meant it. I have two caps in my MMC and they're rated at 2k each. I use 5 440v tvs's. I got 5 from trial and error if i used 4 it would start to conduct before running at full power. I think with 5 I have just enough headroom to where it prevents anything above normal operating voltage.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Bennem wrote ...
EastVoltResearch wrote ...
Yes. Thats why a strike rail is required.
I installed two strike rings.....i guess a third can't hurt.....lol
Speaking of shorted turns - i hope those strike rails aren't closed loops. You need at least about 6" spacing to prevent shorted turns and also to prevent arcing between the loop ends.
Registered Member #154
Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260
EastVoltResearch wrote ...
Speaking of shorted turns - i hope those strike rails aren't closed loops. You need at least about 6" spacing to prevent shorted turns and also to prevent arcing between the loop ends.
Dan
Hi Dan,
Yes I have a spacing in my strike rails, so its not a shorted turn. i had no arcing between loop ends. I think i need to raise my lower strike rail a little, and perhaps a larger diameter upper strike rail.
Registered Member #570
Joined: Wed Mar 07 2007, 03:41PM
Location: Winchester Uk
Posts: 42
Hi Mel,
In theory the larger the diameter of the strike rail tube the less likely it is that corona will form on it at any given power level. Can you go to two toroids on the top to help steer the sparks away from the primary?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Dr. Shock wrote ...
Speaking of shorted turns - i hope those strike rails aren't closed loops. You need at least about 6" spacing to prevent shorted turns and also to prevent arcing between the loop ends.
Dan
I don't know what everyone has with these shorted turns. Toroid is, after all, a shorted turn to, and a big one.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Plasmaddict wrote ...
Dr. Shock wrote ...
Speaking of shorted turns - i hope those strike rails aren't closed loops. You need at least about 6" spacing to prevent shorted turns and also to prevent arcing between the loop ends.
Dan
I don't know what everyone has with these shorted turns. Toroid is, after all, a shorted turn to, and a big one.
The amount of field at the toroid from the primary is relatively negligible. The field from the primary will maximize in the plane of the primary coil, right where the strike rail is. The field then decreases by the square of the distance.
Registered Member #154
Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260
Paul Benham wrote ...
Hi Mel,
In theory the larger the diameter of the strike rail tube the less likely it is that corona will form on it at any given power level. Can you go to two toroids on the top to help steer the sparks away from the primary?
Cheers,
Paul.
Hi Paul, I will increase the diameter of the strike rails...and try adding a smaller toroid under my current one. I still have to get some replacement IGBT's so it may be a while untill i have the coil up and running as these HGT1N40N60A4D's are expensive and not so readily available anymore (but Farnell and Mouser have some left) So....i may have design a bridge layout to take alternative IGBT's.
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DRSSTC Primary strike failures
