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naok

Thu Aug 19 2010, 03:36PM

Registered Member #3128 Joined: Thu Aug 19 2010, 12:23PM
Location: Tokyo,Japan
Posts: 17

Hi all!
I make drsstc according to steve ward's Web site.
But,I could only have 16 inch spark length.(input 100VAC)
I think I have problem my full bridge.

My bridge circuit and waveform is here.

My driver is here.

Please,advise me for big spark!

Goodchild

Thu Aug 19 2010, 08:08PM

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

OK here is your first problem, you modified Steve's driver you didn't have to do that to drive a H bridge, I suggest you build the original drive.

I could probable be of more help if posted some pics of your driver board, H bridge, ect...

naok

Fri Aug 20 2010, 05:10AM

Registered Member #3128 Joined: Thu Aug 19 2010, 12:23PM
Location: Tokyo,Japan
Posts: 17

I see.
But,It is really hard to design my original driver.
My scientific experience was only to have made oxygen when I was a grade-schooler...
But,I made the drsstc after finished a day's busy business work. It has been over one year.

I will upload more picture when I get home.
thank you!

naok

Fri Aug 20 2010, 03:30PM

Registered Member #3128 Joined: Thu Aug 19 2010, 12:23PM
Location: Tokyo,Japan
Posts: 17

My pics is here!
If you request more pictures,I will upload another pictures.

HV Enthusiast

Fri Aug 20 2010, 05:14PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Nice pics. You should twist your power leads together from your energy storage caps to the bridge. This will lower the inductance considerably vs. the arrangement you have now.

Goodchild

Fri Aug 20 2010, 06:48PM

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

Ya you don't need the extra MOSFETs you added in the gate drive, all you are doing is making that part more complex. I would just use 4 to drive one GDT for all 4 IGBT's.

As far as that I don't see much else that is wrong, what PW and BPS are you running?

naok

Sat Aug 21 2010, 05:47AM

Registered Member #3128 Joined: Thu Aug 19 2010, 12:23PM
Location: Tokyo,Japan
Posts: 17

Good morning!

Is "energy storage caps" pair 2700u filter capacitor?
OK!I twist my power leads.
I think I could have little stability.

I deleted the extra MOSFETs and a GDT in the gate drive.
It make very simple the gate drive.

ON period:170us
BPS:120

Secondary:6.5"x22"winding of 30awg magnet wire.Double coat of epoxy for protection.
Primary:10 turns of .25" cu tube. 11" diameter form, .2" spacing between turns, tapped at 3.1 turns.
MMC:7 parallel strings of 2 series .15uF 2kV caps (942C series by CDE).

Filter capacitance:2 parallel 2700uF 400VDC for 5400uF at 400VDC.

Input:100VAC 9A
Spark length:16inch

mmm...

Bennem

Sat Aug 21 2010, 08:41AM

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

Hi Naok,

Its looking good!

other than experimenting with tuning,
What is your OCD set to?
as that may be limiting your spark length
if set too low.

teravolt

Sat Aug 21 2010, 05:11PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

welcome aboard naok, I'm with EastVoltResearch. put the bridge, MMC, and electrolytics as close as possible to each other and mount them under the primary and reduce lead length. This is done to reduce resistive and inductive losses. The other thing is tuning, the primary tank's resonant frequency should be less than the secondaries around 4-8khz. The idea is when the sparks move out they load the secondary and add capacitance say 1-6pf depending on the length of the spark thus reducing its resonant frequency. You may also want to read about frequency splitting.
Do you have a current transformer and oscilloscope to monitor the primary current? Since you only have 100VAC in Japan you may need more input voltage up to 200VAC. A 10A variac and a 1 or 2KVA transformer with a 2:1 ratio enough to handle 10 to 15A would be desirable. Use the current probe and oscilloscope to monitor primary current while adjusting the variac. This is done so you can set the OCD and not go to far with the fets while upping the power. I am not sure what devices you are using and how far you are going to push them outside the safe operating area. Moast DRSSTC's that are built hear push fet's beond there normal limits for short times so the moast power can be delivered to the secondary. This done with a price of burnt silicon and is done sucsesfully with expierience.

the idea is to reduce losses, fine tune, and increase power.

naok

Sun Aug 22 2010, 12:03AM

Registered Member #3128 Joined: Thu Aug 19 2010, 12:23PM
Location: Tokyo,Japan
Posts: 17

I uploaded pulse form movie.

If you request more movie,I will upload another.

By the way, my secoundry ground is setting on window frame.
I think it's too small.
is this a problem?

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