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Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
I've been building a SGTC from junk in my shed, and it was outputting nearly 80KV to something in the air, it is powered on 65W ZVS, and I was happy, but the capacitors were to small of voltage (275v~ capacitors) and I need new cheep cheapy ones, anyway websites where I can buy ones?
I'm not making homemade capacitors, they fail all the time.
I'm using MKP's rated at 275volts and a bunch of other capacitors rated at like 700~ volts.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi platinum,
Again -
I hardly know of a better bargain for polypropylene caps for now, I'm sure you could build a working MMC with them with just some $10 + shipping.
The caps probably aren't as resistant as CDE series, but I'm quite certain they will work for a small tabletop SGTC. And if you would finally provide exact data on your coil, we could calculate out what size of an MMC you need.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
m4ge123 wrote ...
Do you know how much current those caps can take?
I tested them for RMS current by taking a single cap putting some 5A RMS at 1Mhz through it. After some 10 minutes, without cooling the cap started swelling up and losing capacitance - so I guess this was over the limit for operation without forced air cooling. After I added a fan to cool the cap, it ran with this load indefinitely just fine. Without fan, I'd say limit would be some 3 amps or so.
So I conclude the caps have pretty good RMS current rating considering their capacitance!
The question I don't know an answer to is how much peak current could the caps take before their ends start burning off. Someone would need to verify that to make them usable for bigger coils. But considering Platinum's coil is quite a tiny one, and he's already using MKP caps I'm pretty certain they'll work for his coil.
Just make sure it's properly tuned and the cap bank is fairly sized (with 50 caps total, it really should be!)
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Well I have a massive relay from a microwave, and it's about 2 times thicker than hair (is it too thin?) and I can't wind it on my coil form, it's incredibly hard by hand, is there anyway to speed it up?
Registered Member #4118
Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140
Tape a handheld drill down to your bench or something and connect that to the secondary somehow. Since you say twice as thick as hair, do you get about 100 turns per inch?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Platinum wrote ...
Well I have a massive relay from a microwave, and it's about 2 times thicker than hair (is it too thin?) and I can't wind it on my coil form, it's incredibly hard by hand, is there anyway to speed it up?
Well, for a miniature coil, thinner wire is better, but less than about 0.1mm will be very hard to wind without breaking it, you'll need to have nerves of steel for that.
Thinnest I used was wire from contactor relays which is about 0.1mm thick; I couldn't be bothered winding thinner than that.
There are no particular tricks, just use a right length nail and a drill controlled by a variac. It would also help a lot to have a buddy control the variac.
After you get used to going fast the whole coil can be completed in like 10 minutes... if your wire overlaps, unwind that bit and start it again.
Make sure to varnish the coil immediately after winding to prevent the wire from unraveling.
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I need caps ¬¬
