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Interesting SSTC circuit

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Steve Conner

Sat Jun 16 2007, 03:21PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

OK, here goes:

The 555 is just an interrupter, which shorts out the gate drive via T3.

R1 and R2 are what get the circuit started by turning one of the FETs on slightly, at which point it cranks itself up by positive feedback.

The MOSFET gates are driven directly off the current transformer. The huge mass of diodes 1, 2, 3, 4, 5, 8, 9, 10, 11, 12 serve to take the current transformer signal and clamp it to a safe value. D1, 2, 3 clamps it to a few diode drops above 13.5V and the remaining ones clamp it to 6 diode drops below ground. (Why he chose 6 diode drops, I have no idea. Maybe he got both MOSFETs turning on at once otherwise.) Anyway, it follows that if you want to use a higher supply voltage, you have to make sure the cathode of D3 still connects to 12V, so as not to lose the gate drive clamping action.

Since it uses the push-pull centre tapped circuit, he had to use a sizeable snubber, which in this case is made of D6, D7, C8, R6, R7.

As regards scaling up the voltage, Vladimiro Mazzilli made a similar circuit a while back, but using 1200V IGBTs and running off rectified 220V mains. It also was current-fed with a tuned primary, so the old pi*Vin thing applied. FETs from a UPS would probably be rated at no more than 60V.

Coronafix

Sat Jun 16 2007, 08:48PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Thanks Steve, I was looking at the second link, his Skori Mini Tesla II.
He uses 60V 100A FETs, the UPS FETs I have are 55V 60A, so I figured they would do fine. I wasn't talking
about using them in a scaled up version, I'd have to start simple first.

Mike

Sun Jun 17 2007, 09:48PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

really cool find. I spent a while talking with a hungarian person and translating the parts list. Here it is!
Resistors:
R1 330 ohm 1/2 watt metal layer resistor
R2 38 kohm 1/4 watt metal layer resistor
R3 80 kohm 1/4 watt metal layer resistor
R4 2.2 kohm 1/2 watt metal layer resistor
R5 22 kohm 1/2 watt metal layer resistor
R6 168 kohm 1/4 watt metal layer resistor
R7 168 kohm 1/4 watt metal layer resistor
R8 10 ohm 1/2 watt metal layer resistor
R9 5 ohm 2 watt metal layer resistor or wire
R10 2.2 kohm 1/2 watt metal layer resistor
P1 100 kohm linear potentiometer

Capacitors:
C1 2200uF 25V capacitor, low esr preferred
C2 2200uF 25V capacitor, low esr preferred
C3 6.8uF 63V Capacitor that tolerates impulses (MKS)
C4 7-15nF non-ceramic capacitor, value has to be determined experimentally
C5 100nF 100V Capacitor that tolerates impulses (MKS)
C6 100nF 63V Capacitor, not ceramic, pulse tolerant (MKS) preferred
C7 100nF 63V Capacitor, not ceramic, pulse tolerant (MKS) preferred
C8 22nF 63V Capacitor not ceramic
C9 1000uF 16V Capacitor
C10 22uF 16V Tantalum Capacitor
C11 2200uF 25V Capacitor, low esr preferred

Transformers:
TR1 30/15 windings (30 windings towards L3) cca. AL2000 iron core without air space | small ring-shaped iron core is recommended

Coils:
L1, L2: 1 winding? on 110mm diameter, thick coated wire, the wire of the two coils are twisted together or made of multi filar wire or an ?IDE cable? where every 2nd "circuit" is connected paralelly
L3: 1000-1800 winding? made of 0.1-0.2mm CuZ wire, rolled on a plastik tube with diameter=63mm
L4: 30-50uH 2A, value has to be determined in an experimental way, L4 C4 "resonating circuit?" has to resonate where L3 does (Tesla secunder)

Semiconductors:
T6 BUZZ11 or similar ( cheap) fet but one with much less current is enough (atleast 1A)
T1,T5 BD242c 3A 100v PNP or simmilar transistor (both on heatsink)
T2,T3 IRF3205 100A 55v N low channel mosfet or similar, but one with smaller current is not suitable
T4 BUZ11 50v 29A N channel mosfet or similar (IRFxxx etc) one under 20A is not practical because rds needs to be small/low
Z1 ZP51 51V- Zener Diode
Z2 ZPY15 15V-os zener Diode
D10-D14 1n4007 1A average Diode
D3-D7 1n5819 40V 1A schottkey Diode
D1,D2 SF18 600v 1a 35ns side by side
IC NE55 or compatible, the well known cheap 555 timer, but the cmos version (7555) is not suitable

Andrew L.

Sun Jun 17 2007, 09:53PM

Registered Member #515 Joined: Sun Feb 11 2007, 02:06PM
Location: Slovenia/Ljubljana
Posts: 94

Wow that's great Mike

thanks.

Coronafix

Mon Jun 18 2007, 01:10AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Thanks Mike, I spent a while myself with a Hungarian dictionary translating it.
Looking forward to building this.
Spent some time yesterday redrawing it in AutoCad as I couldn't print it from the web page.

Coronafix

Mon Jun 18 2007, 10:10AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Oops, here's the drawing.

] 1182161436_160_FT26972_skori_mini_tesla_ii_model_1 .pdf[/file]

Mike

Mon Jun 18 2007, 04:45PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Very nice thanks goldsphere. Looks like we now have everything in english and able to print out to create it :D
Thanks

teravolt

Tue Jun 19 2007, 04:39AM

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

helo everybody I found this mosfet at digi-key IRFB3077PBF. 75v 210A what do you think

teslaguy

Sat Jun 23 2007, 10:08PM

Registered Member #617 Joined: Fri Mar 30 2007, 07:29PM
Location: Buffalo NY
Posts: 49

would this be a good coil for a beginner to build? I found most of the parts at digitkey and its in my price range.

Part Scavenger

Sun Jun 24 2007, 03:11AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

HM2004:
I would go with this one here:

That is an extremely popular and tried SSTC design, Tons of people have built it and it's easy to put together and understand. Need any help, just post a thread, PM me or whomever/whatever. This is a good place to be for that sort of thing.

PS, 4HV's nice to noobies, but there's kinda a *thing* about hijacking threads...

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