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Ken M.

Wed Jun 13 2007, 02:23AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Well the wire came in today while I was at work, for the SSTC that I'm working on. Which is built on Steve wards Mini-SSTC, with almost identical specs...coincidentally. Still waiting on parts to arrive for driver and power electronics.

So far here is the progress, I managed to get all 18" on the coil wound with 30awg wire in about 3.5 hours.

The pictures of the finished coil on the winding rig, and on a table finished and drying. The rig is two lawn chairs supporting a threaded rod that ran between the two chairs and in the middle of the coil.

I sorta fixed the linking, For some reason the image resizing thing isn't working for me anymore.

Update: Sat 10AM:
Well All my parts came in on Thursday and I started working on it so far everythings working fine minus the little GDT issue but I believe thats been fixed. Tried to build the remote interuptor, but it failed so I'm gonna try and fix that today after I get a new perfboard from Radioshack along with some thermal compound since I'm out, I'll add some pics of the progress after I get everything soldered and boldy go into the 120VAC powering stage.

Things to do still:
Make remote interuptor work in control box
Solder drive and power electronics to perfboard
Hook up coil to electronics and test
Make topload
Make housing\stand for entire system
Post pics on forums of progress

Update time 11:30PM saturday!
Well got everything soldered and on the perf boards was testing UCC outputs when the 1st casualty hit

,luckily I had a replacement one, after I got that I figured it was time to take a pic of the boards progress before I got the power caps, power lines, and recovery diodes in

, Well Managed to get the whole setup semi wired and tested and here what the setup looked like

,Fired her up and was getting kinda crapy arcs almost as if I was just running a micro coil with 5v's input, it was enough to put a blue plasma ball ontop of the wires tip, and arc to a florescent and light it up, but other then that it was crap, Except for whe never I'd switch to a different interuptor value it would do a massive 4in discharge (So no pics of it running

). Anyways I switched the primary coil around and stopped teh interuptor halfway between two settings and I was able to produce some really nice arcs for about 10seconds then the dining rooms circuit breaker popped (20A)

, left the power electronics plugged in and flipped the breaker then Boom the (-) rail fet's gate drive resistor flashed over I think...

. Just noticed I forgot to insert the pics of some of the setup,

...

Wed Jun 13 2007, 02:40AM

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

Your links are broken in several ways.

In any case, how much power are you planning on running?

Ken M.

Wed Jun 13 2007, 05:41AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

As for power....I guess what ever the bridge rectifier will limit it to...which is 10A, so I guess 1.2kW. I never really thought of how much power I was going to put into it...

EDY19

Wed Jun 13 2007, 04:35PM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408

I'd get a bigger bridge rectifier- with a secondary that size, the rectifier will most likely be the limiting factor- I had a 10A rectifier, and was running 16 inch sparks on a 4" by 12" secondary- however, CW i was drawing nearly 2kw, and the rectifier blew after some time. What MOSFETS or IGBTs will you be using?

Ken M.

Wed Jun 13 2007, 10:49PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Irfp260n's I'm gonna follow the schematic to the letter almost, unless a part is either obsolete or not specified. If thats the case though Edy, what you you or anyone for that matter suggest, with the exception of a variac? Also would one say make a helical primary out of Cu tubing and have it about 1\2"away, or just find something to cover the lower part of the secondary and just wrap large AWG wire around it? Now this questions got me wondering, since having sharp points, i.e if I bend the output wire a say a 90 degree turn to connect to the toploads bolt, it would act as a discharge point, but what if I make a Plexiglas disc, and make a trace out of Al tape from the bolt to where the wire makes the bend, would it still act as a discharge point or would it help convey all the energy to the topload bolt?

Brett Miller

Thu Jun 14 2007, 12:31AM

Registered Member #593 Joined: Tue Mar 20 2007, 12:32AM
Location:
Posts: 50

Whitearc,

I would use some poly sheeting of some type to wrap around the base of the secondary for insulation and wind a 4-5 turn primary directly over it, near the bottom of the secondary. Just a few minutes ago I was running my very similar system with a smaller 3" secondary (my 4.5 x 12.5 is in use in another TC project right now). I used a primary that was wrapped around a 4 inch pvc section for 4 turns. This setup gives a definate decrease in spark when compared to running the same 3" secondary with higher coupling. Several inches difference in fact. If you really want longer sparks I would go for the higher coupling. It's pretty important in this type of system. After I built Steve's Micro and Mini SSTC projects, I did a lot of comparitive tests playing around with varying degrees of coupling. I also used both drivers to ring all the secondaries I have around the lab and take notes on their Fres while wearing various toroids, and unloaded. This allowed me to have a good perspective about the effects of different primaries. Generally higher coupling resulted in hotter and longer sparks, but if too high resulted in more heating of the mosfet. Especially in CW mode this becomes significant fast. However, with secondaries in the 100Khz vicinity, my IRFP260N's ran cold in CW mode, until I started drawing constant power arcs. Even then it was amazing what they could hold up to. I still haven't blown the ones in my half bridge.

Some people have used sections of a 2-3 liter bottle, cut out and electric taped onto the secondary windings, I used some cuttings of plastic from the large 1 gallon zip lock bags. One thing you might do, if you have any, is use neon sign high voltage wire...however I've only seen that up to about 16 gauge, and I prefer using 12-10 AWG for my SSTC primaries.

-Brett

Dago

Thu Jun 14 2007, 09:04AM

Registered Member #538 Joined: Sun Feb 18 2007, 08:33PM
Location: Finland
Posts: 181

Brett Miller wrote ...

Whitearc,

I would use some poly sheeting of some type to wrap around the base of the secondary for insulation and wind a 4-5 turn primary directly over it, near the bottom of the secondary.

I wouldnt suggest doing this based on my own imperical tests :P Heres my SSTC running where you can see the primary:

The secondary has a few layers of polypropylene wrapped around it and the primary wound directly over it, it DID produce longer sparks than with a lower coupling but then a bit after that pic it arced over killing the FETs.

Ken M.

Thu Jun 14 2007, 10:34AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Yea I figured even if I used the 2 liter bottle idea, using several bottles and layering the plastic, that the voltage on the secondary would still be arc through or over. The one thing I can't remember though, is do you connect the ground of the secondary to the ground terminal of the RFI filter (I think not, but still asking), or do you just run a decent sized to a pole in ground?

EDY19

Thu Jun 14 2007, 01:36PM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408

For one, if you are running only 1.2kw which is limited by your rectifier, there is little reason to use copper tubing in the primary- I used 10 or 12 gauge wire in my primary- much cheaper, and didn't get warm when running ~2000W. I would really recommend using a bigger rectifier though, its not a big cost item, and It will allow your coil to run at much higher powers which that size secondary is begging for

Try :

Ken M.

Thu Jun 14 2007, 03:57PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Well I got the electronics in today, and it turns out...I forgot to read my order on the value of the bridge, which is actually 15A 400v. Its funny that you say use 10awg, because I was thinking of doing some low V tests and managed to dig up some old 10awg, that I previously used as a power wire for a car audio system, before I bought the huge 3 awg and 100amp fuse for the car, lol. Now the only tasks I have left to do, get a primary insulator(a tube to isolate the primary and secondary, as well as providing a place to wrap the primary around) Prototype the electronics on a bread board, get a perf board, enclosure for the remote interrupter, low voltage test then wire up the whole thing and assemble it on a wood or plexi glass stand put a mesh cage around the electronics! All before Monday when I start my new job YAY!~

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