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colin heath

Tue Jul 21 2009, 09:06AM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

OK having had a think on the problems I dont think there is anything major going on. The toroid I will make a conductive joint in today which should solve problems. I am sure that tape is non conductive until high voltages then it conducts and the tuning of coil changes.

Second problem with flashover is apparent in this video

This is the end of the primary with no cap on it so a nice sharp edge to cause the problem so easily recitifed.

I will look at these today and see how it works out. I also need to figure out adjusting the current limiting as it hasn't cut in once yet so maybe I have pto wound too far up???

Bennem

Tue Jul 21 2009, 09:42AM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

colin heath wrote ...

I will look at these today and see how it works out. I also need to figure out adjusting the current limiting as it hasn't cut in once yet so maybe I have pto wound too far up???

Hi Colin,
Are you using approx 1000:1 (2 x 33 turn ferrites) for your OCD feedback?
and what burden resistor have your chosen?

Does tuning/ coupling adjustment make any difference to your racing secondary sparks?
All the best,
Mel

colin heath

Tue Jul 21 2009, 10:24AM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Bennem wrote ...

Hi Mel,

yes using that transformer arrangement. I will have to look up burden though as can't remember what it is:-p

I think the coupling was too tight but due to noise I had to pack up last night before upsetting neighbours. I am going to knock up a new base for secondary this afternoon so I can adjust coupling while keeping sec secure. I think the tuning is the major problem as it changes when the toroid arcs over bad joint then making it a different capacitance.

Cheers

Colin

Herr Zapp

Tue Jul 21 2009, 03:44PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Question for Steve McC -

Back in your post of June 12, you included this schematic, showing where the "synch" signal originated:

I didn't look closely at the schematic till now.

What are the components labeled "LCL1", etc? I just don't recognize the symbol.

Regards,
Herr Zapp

Steve Conner

Tue Jul 21 2009, 04:03PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

They're Murata LCL filters. Basically a ceramic disc capacitor with three legs, two of which have ferrite beads on them, and the whole lot encased in the same goop they use for ordinary ceramic discs.

Bennem

Tue Jul 21 2009, 06:28PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Hi Colin,
I don't know if this will be of any use,
but here's a link to a list of racing sparks causes,
just in case the problem dosn't turn out to be your toroid.

Mel

colin heath

Tue Jul 21 2009, 10:41PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Thanks Mel, I would most certainly say it was coupling issue. I stopped being lazy and made a proper base for secondary fully adjustable. Raised it a good few inches and was running really well. Then the it all went dark !!!!

Blew both IGBTâ€™s even though I actually lowered on time in last bit of run!!! Anyway as was removing them noticed I had forgotten to tighten them down properly and have suitably punished myself since. Refitted new with heatsink compound and pulled up nice and tight this time.

I will be running low power for some time tomorrow and scoping out bridge along with gates etc as just want to check nothing else caused it. I would say not though as they failed short ciruit, unless it was latch up or shoot through but think it would have blown before that if it was case.

Anyway will keep you posted on results. I will have a little ceremony later for those beautiful IGBTâ€™s

Coronafix

Tue Jul 21 2009, 11:19PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Looks like the coupling is too tight. If you raised your secondary up it should be all right. Perhaps if you started with bottom turn of secondary in line with top turn of primary. Once tuned completely you can lower the secondary until you find the perfect coupling without flashover.
Looks super good though, well done.
Michael

Edit. Sorry, missed seeing your last post.

colin heath

Wed Jul 22 2009, 12:12PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

OK did some scoping this morning and I am quite surprised that things look pretty good. gate drive waveforms look ok with no ringing perhaps a little rounded. scoped across dc bus with differential probe and got nothing that looks too dodgy. I did notice the bursts seem at 150khz and my gates running 100khz???

Maybe not looking in right places but it doesnt look too shabby at all. Gate waveforms do fuzz a little at higher power.

Found performance problem at higher power and why sound changed........Current limit LED wasn't working but was doing it's job. So I have replaced LED but need smaller resistor in line now as still very dim when lit. I have wound current limit right down and restricted streamers to around 1 foot. I need some way of measuring voltage going into this section though so I can setup properly at correct current.

So ready now for some good weather to let this thing loose once i suss current limit. Otherwise it's a bit like winding out the safety gap until it stops firing without knowing why

Bennem

Tue Jul 28 2009, 07:30PM

Registered Member #154 Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260

Hi Colin,
Hows the progress coming along?
Any updates?

Mel

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