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My first DRSSTC

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Dr. Drone

Fri Jun 29 2007, 10:36PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
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Posts: 1673

Danielle

Fri Jun 29 2007, 11:54PM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

thanks I will be using some 160N60s so that may help but here are some more pics now I have more ultra bright LEDs

Danielle

Tue Jul 03 2007, 02:35AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

ok so now I finally ordered my wire PVC pipe and MMC caps they will arrive next week on Tuesdays so I should be finally done on Thursday my final question is that the wave form of the GDT first does out of phase and then goes back in and then has a strange low frequency sine wave after, that isnt ringing. I might be able to post a pic on Thursday but I know its not like what I have seen before I dont understand why this happened and would like to know if that off phasing is normal .

Steve Ward

Tue Jul 03 2007, 04:36PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

my final question is that the wave form of the GDT first does out of phase and then goes back in and then has a strange low frequency sine wave after, that isnt ringing. I might be able to post a pic on Thursday but I know its not like what I have seen before I dont understand why this happened and would like to know if that off phasing is normal .

Out of phase with what??

Also, until you have it loaded down, the entire wave form may tend to oscillate up and down (at a frequency maybe 1/4 of the operating frequency). This, as well as the damped ringing after the gate drive shuts down is caused by the leakage inductance of your GDT oscillating with the series DC blocking cap on the primary of the GDT drive. Usually the ringing at the end is negligable (i usually see about 2V MAX).

But please, post a picture if you want an accurate opinion of what is going on with your setup. Also, dont worry about it much until you actually have the IGBTs connected, because that is the condition to worry about.

Danielle

Tue Jul 03 2007, 07:24PM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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thanks I do think this is causing the ringing because it looks exactly like you described I should have a pic tonight but I would like some help with calculating the MMC sise I bought 12 CDD tesla caps the 2000v .15uf The length of the primary is also up for debate I was thinking of making it around 36" it is 6" OD PVC light green pipe. I am getting it on the 5th so total time till completion might be in time for my birthday if I work really hard. My last question is should I control the HV power supply with a variac or could I just use the on timing?

Thanks,

Daniel.

Steve Ward

Tue Jul 03 2007, 08:16PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Given that your IGBTs are rather small in size, i would expect maybe 4-5 foot sparks. A 36" long secondary will be really much larger than necessary. I would rather suggest something around 20-24" long. Ive produced up to 80" sparks from my 22"x6" coil, to give you an idea of how robust these things can be.

If i was limted to 12 caps, i would do 4 strings of 3 in series. Use javaTC or something to figure out how much primary inductance you will need for your secondary and toroid. I usually aim for a coupling around .18-19, if you want to get some idea of how to space things out ahead of time.

Danielle

Fri Jul 06 2007, 11:26PM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

ok so I have now finished my secondary and epoxy coated it it is 24" tall 6.21"OD here are pisc of it and everything ive done I also am posting the un loaded scope images

Things left to do:

Trim secondary and mount toroid and mounting plates.

assemble power electronics and heat sinks.

assemble MMC

put everything together.

oh yah also its my B-day today I wanted to show it off at my party so I made the party on the 14th so I have plenty of time.

edit

MMC done

secondary is trimmed and taped.

toroid construction is on its way

I may be done early next weak

Toroid is done

Danielle

Sun Jul 08 2007, 02:47AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

ok so here is the finished coil with toroid and I am almost done

Steve Ward

Sun Jul 08 2007, 07:46AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Yikes, those gate waveforms look really bad. Either the GDT is not too good, or you dont have a proper DC blocking cap on the primary side.

Bennem

Sun Jul 08 2007, 04:12PM

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

Nice construction!!
I especially like your plexy primary mount!!
Wish i could make something so beautiful.

All the best with first light!..

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