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DRSSTC trouble need help

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Goodchild

Wed Dec 30 2009, 06:55PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Ok so this is the first DRSSTC ive ever built ive built SSTC and SGTC in the past and now i'm challenging my self with this amazing device, and challenging it is! The people over at Tesla Universe have been a big help so far, but with being a very strange problem I thought I would open it up to a bigger base of people.

Ok for starters the specs of the coil:

Secondary: 18x4.5 inch on ABS form 32 gage wire (2250 turns)
Bridge: full bridge of HG48AB30N60A4D IGBTs (latter will be upgrade to IXGN60N60C2D1)
Bus cap: 3300uF 400v
MMC: 0.2014uF 14Kv 5Kvac
primary: 12 turns of 0.25 copper tubeing 5" tall by 9.75" wide
topload: 18x4.5 inch spun toroid
controller: Steve Ward's DRSSTC controller

Feedback: Primart current feedback with OCD (2 33 turns casdade total of 66 turns on 2 cores)
Fo: 91Khz (this is with topload)

Here is a pic of my testing setup:
4223258327 Eb2e9227e2

Ok so the problem here is I can't seem to get sparks out of the dang thing, well I do get like little baby 1cm sparks and Ive had up to 1 inch or so but I know this is not right. The primary current waveform with no secondary looks good to me.

(yellow is primary current blue is the output of the OCD recifier)
4225915165 8244028bd6 O

With no secondary in place the OCD comes on at about 35VAC with secondary in place it come on much quicker, at first I though this was just the secondary but I dropped in a same sized secondary (known to work) from my old tesla coil and it did the same thing.

Here are the current transformers:
(all 3 are identical green CT is for the scope with a 10 ohm resistor)
4227420558 Ebb108dd73

I have a feeling that it is something realy stupid that I overlooked.

Any help would be great!
If any more info is needed just tell me and I will get it.

Andri

Wed Dec 30 2009, 07:58PM

Registered Member #1533 Joined: Wed Jun 11 2008, 02:13PM
Location: ReykjavÃk, Iceland
Posts: 46

Have you tried swapping the wires from the feedback ct?

Goodchild

Thu Dec 31 2009, 05:21PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

I have found the problem it's my OCD it was tripping to early. At least I know what the problem is now here is a vid of it throw some nice 2.5 foot arks with OCD disabled

keep in mind this is untunned at 1/2 power at 120v no doubler.

Z28Fistergod

Thu Dec 31 2009, 06:27PM

Registered Member #2040 Joined: Fri Mar 20 2009, 10:13PM
Location: Fairfax VA
Posts: 180

Well crank it up already!

Nice looking construction. I especially like the bnc connector on the CT.

Goodchild

Fri Jan 01 2010, 05:38AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Thanks for the nice comments. This coil is now full operation as it was a problem with the original CTs.
Now that the coil is fixed my arks max out a about 2.8 to 3 feet at 200A of primary current (this is at 100% of my
120V variac and at 100uS on time). I will have to get a step up transformer to get 240VAC for better performance, any
step up transformer suggestions?

Killa-X

Fri Jan 01 2010, 08:58AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Goodchild wrote ...

Thanks for the nice comments. This coil is now full operation as it was a problem with the original CTs.
Now that the coil is fixed my arks max out a about 2.8 to 3 feet at 200A of primary current (this is at 100% of my
120V variac and at 100uS on time). I will have to get a step up transformer to get 240VAC for better performance, any
step up transformer suggestions?

Was this variac to a direct feed? Or did you do the common large capacitor doubler, to take 120VAC rectified to 170VDC, and then doubled? I noticed most DRSSTC diagrams include a voltage doubler, which consists of 2 capacitors, and 2 diodes.

Goodchild

Fri Jan 01 2010, 07:44PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Yes but I find that a step up transformer is 1 easier to hookup 2 cheaper and 3 easier to obtain then large diodes and caps. I will feed the output of my
240VAC step up into my rectifier and bridge cap circuit which is already set up to hand up to 400V.

Till my new step up transformer comes in the mail here are some pics and a vid at full power (120VAC in 100uS)
4233814283 9556670788

vid:

more photos here:

Bennem

Sat Jan 02 2010, 09:21AM

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

Looking good!!

What have you got your OCD set to for this test?
you mentioned earlier that you had disabled your OCD.

All the best.

Mel

Mads Barnkob

Sat Jan 02 2010, 12:44PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

A stepup transformer that can handle the potential powerdraw of this coil is not exactly easy to find or cheap, a voltage doubler is easiest to make as you can find diodes and large lytics cheap and easy :)

Goodchild

Sat Jan 02 2010, 05:17PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Bennem thanks for the nice coment and also the OCD is set for 200A, I can't evan trip it at full power. Primary current stays at about
180A for that run.

Mad Barnkob I did find a step up transformer on ebay a rather cheap price to, brand new it's rated for 1000W
and it only cost me $60.

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