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Tom540

Mon Jul 09 2007, 01:44AM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

Well Ive finally decided to post something in the projects section. Now let's see if i can not screw up posting pics.

I threw this coil together while waiting for some stuff from Ebay (which still haven't arrived). I am quite proud of how it turned out as far as looks considering I didn't plan anything.
-OKay specs-

Secondary: 2.5"x 13" ABS w/27 AWG wire Fo ~500KHz w/topload
Primary: pretty obvious 4 turns of some .250" copper tube cause I had it laying around
MMC: 2 .15uF 2000v CD Caps in series w/bleeders
Bridge: H-Bridge of irfp450 Mosfets, 160V smoothed DC on bridge
Toriod: 6"x1.2" Flex loom, Bondo filler and alu tape.
It uses secondary base feedback 74HC14 too smooth and then ucc drivers and it has Steve Ward type Interrupter built in.

and now some pics.....and video which I had made before I finished the coil.

]1183945367_487_FT0_minigreen.wmv[/file]

Well I increased the interrupter speed and added a second interrupter to modulate the first interrupter.

-Tom

CT2

Mon Jul 09 2007, 02:31AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

Looks great! I like the nice black base you made, along with the control boards, they look professional. Question though, I assume your running it DR (because of the MMC) but your using MOSFET's? I didn't think they could handle being run that way, and it doesn't even look like your heat sinks are too big either...

Tom540

Mon Jul 09 2007, 03:47AM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

Hey thanks!,

It's not running DR It's got an MMC because actually I just had those caps and decided to spare them. I suppose it could probably run off one of them but i really didn't measure anything and I don't have a clue how much voltage is across those caps. lol They get a little warm after awhile but this thing could probably run 15 min or longer.

-Tom

CT2

Mon Jul 09 2007, 04:56AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

I see, so what is the MMC in the circuit for then? Are they in series with the primary? Just wondering why you included them is all haha

...

Mon Jul 09 2007, 05:15AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Presumably they are DC blocking for the primary...

In any case, that is a really sweet SSTC! And those sparks are extreemly good for measly irfp460's! Although is there any reason that you can't turn up the break rate a little?

Tom540

Mon Jul 09 2007, 05:47AM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

lol, oh yeah the break rate. Well I was gonna make it really slow pulsed with long bursts but I could bring the break rate up quite alot. I figured it wouldn't get hot that way. Well I guess I'll be turning the break rate up.

ShawnLG

Mon Jul 09 2007, 05:55AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

Nice coil. I like the green secondary.

"Question though, I assume your running it DR (because of the MMC) but your using MOSFET's? I didn't think they could handle being run that way,"

How come MOSFETs are not good for DR?

Bennem

Mon Jul 09 2007, 07:08AM

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

Wow!....another excellent constructed coil!
I enjoyed seeing your last couple of small DRSSTC coils working on
You Tube.

I'm a bit confused too as to why the two MMC caps in serise
with the primary.....so its not a tuned primary?
if so...perhaps thats why you can use Mosfets?

Once again...nice coil!!

Mel.

...

Mon Jul 09 2007, 03:37PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

The caps are just there to prevent a DC current from running through the primary, which can happen if the duty cycle isn't exactly 50%. The value isn't critical, just enough that they don't cut off the 500kHz as well..

You can't use MOSFETS in a DR coil, as DR coils have insane peak currents (hundreds/thousands of amps) and MOSFETs don't take insane peak currents nearly as well as IGBTs do. This be because a MOSFET in saturation will have a (more or less) fixed resistance, about .5ohm for a irfp450, where an IGBT has a fixed voltage drop, usually about 2v. Because of this, the power disapated in the switch goes up as the square of the current with a MOSFET, but is linear with an IGBT, so with you have huge peak currents you are much better off with an IGBT.

Dalus

Mon Jul 09 2007, 04:45PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

You can use mosfet's in a drsstc just check this out

But it's only possible with carefull building and tuning.

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