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SSTC toroid heating up

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LAN_403

wylie

Sat May 01 2010, 03:41PM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

It seems more likely that any temperature rise the toroid experiences is the result of heated air rising from the driver circuitry and/or the primary,

Or heat conducting from the breakout point?

Another thought, but it relies on the topload being one plate of a capacitor to ground; that was my understanding, but if its wrong then ignore this idea

If the topload comprises one plate of a "low-value capacitor to ground", a multipart topload with insufficient connectivity between the parts might raise the ESR of that "capacitor", leading to increased heating at higher freqs.

Just a thought.

brtaman

Sat May 01 2010, 04:48PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
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Posts: 247

On my H-bridge sstc, the torroid got so hot on 5 minute runs that it actually started melting my LDPE secondary former. It just "sat" atop it.

Never really looked into a cause, just assumed that it was due to the high power input XkW. The breakout got hot enough that it started glowing, so some heat came from it as well.

MRacerxdl

Sat May 01 2010, 11:08PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

The thermocouple come with the multimeter, the multimeter made the calculations and show the correct temperature. So its not calculations problems. I would prefer a IR temperature meter, but I dont have one. About the ground, I didnt get any uV on the ground, I am only a 1 or 2 meters away from the bar on the ground, so I think it shouldn't have any voltage on the ground (not even a uV measured).

And the toroid temperature doesnt seen to change when I remove the toroid from the top of the coil for measure, only the natural temperature decay by the heat transfer to ambient.

About the Heat rise by the air, I dont think its that, because all the circuit is at ambient temperature, heatsink, mosfets, primary, secondary. Only the toroid is getting heat.

About the distance of the top of the secondary from toroid, it maybe be that, as I didnt try to raise up more than a few cm, and the toroid has ~9cm diameter. As I noticed that heat gets a little bit lower when I raised up 1cm, that can be the most probally cause.

Other thing I noticed, changed my interrupter, to make a Lower tOn and higher tOff (like DRSSTC's one), made the temperature lower to a little heat only, I think 28ÂºC for a 22ÂºC ambient temperature. Maybe the distance between the top of the coil from the toroid is the problem?

Herr Zapp

Sun May 02 2010, 12:23AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

MRacerxdl -

Your thermocouple temperature measurement technique looks reliable. Since you state that your driver circuit and especially the primary coil is also staying near ambient temperature, then the toroid heating seems to be real.

Resistive heating from the "shorted turn" transformer aspect, or simply eddy-current heating? Is your toroid built around a conductive center hub? If not, it might be interesting to "disconnect" the ends of the duct that form the toroid to eliminate the shorted turn, and see if the temperature rise remains unchanged.

One additional question: what material is the smaller toroid (directly above the secondary) made from? Is there any possibility that this is a coiled-steel spring covered by metallized plastic film?

Regards,
Herr Zapp

raff

Sun May 02 2010, 01:04AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

MRacerxdl wrote ...

Other thing I noticed, changed my interrupter, to make a Lower tOn and higher tOff (like DRSSTC's one), made the temperature lower to a little heat only, I think 28ÂºC for a 22ÂºC ambient temperature. Maybe the distance between the top of the coil from the toroid is the problem?

maybe so.. 9cm diameter topload halved is 4.5cm = distance between end of secondary winding to end (bottom ) of the torroid diameter ..... OR 9cm (end of winding tip to CENTER of topload area)..

adding a few "loose" turns 1/2cm to 1cm distance(per turn) prior to connecting the topload also

MRacerxdl

Sun May 02 2010, 06:13PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

The smaller toroid is a plastic duct with adesive aluminium foil (its really alu not metalized plastic).

I added 5cm between the end of coil and the smaller toroid, with a Paper Disc.
The sparks increased 8cm at end and the toroid doesnt seen to be heating anymore. I think that was the problem...

Now I need to make it beautiful, because the spacer doesnt look good :P

Thanks all for the help, soon I will post the results at my Zarc SSTC topic on projects :D

Thanks

dillon

Sat Aug 08 2015, 03:29PM

Registered Member #54416 Joined: Wed Feb 04 2015, 01:30AM
Location:
Posts: 13

I have a very radical theory, maybe you tesla coil is acting on the same physics of an airconditioner. A capacitor compresses , and when you compress gas anyway it gets hotter. I have a 5kw zvs parallel tesla coil and my primary capacitor heats up a little ,maybe 5 degrees, but my primary coil which has 200 amps circulating actually cool down by 15 degrees and will collect large amount of condensation. also secondary coil which has about 5 amps going through 130 ohms nevery heats up at all. my toroid does heat up about 5 degrees. edit , when I was using 10 awg on my primary it got super hot, but with 8 awg it lower temperature. None of this makes sense to me.

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