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Registered Member #4073
Joined: Sun Aug 28 2011, 08:43AM
Location: Australia
Posts: 17
I started winding my secondary coil for Steve Ward's mini SSTC (this is my first TC). I got most of the way through, before I ran out of wire about 2.5cm from where I hoped to finish.
The coilform is 90mm diameter white PVC pipe, and the wire is 34awg (I'm guessing) copper enamel from a micro-wave cooling fan. The half bridge will run off full bridge rectified Australian mains (hopefully), but I will first test it through a 240-120v isolation transformer.
I modelled the coil as it is now on JavaTC and it's specs are in the attatchment. The coil is modelled with and without a topload. The topload will have a breakout point.
Is it worth continuing to wind with a seperate spool, or if the coil will work fine with / without a topload? If any other details are needed, just let me know.
Registered Member #4052
Joined: Thu Aug 11 2011, 04:43AM
Location: IN ,USA
Posts: 69
Your coil does not have as many turns as the original, so it does have a higher resonant frequency. SSTCs tend to be sensetive of higher frequencies, however this does not really matter unless you go really high. Also a large topload can help keep the frequency down.
I just finishedSteve Ward's mini SSTC design myself. My secondary with a topload, in a faraday cage is ressonant at about 350KHz, and it works great, the MOSFETs do not heat up at all.
Watch for stray inductance though. I did not pay attention to this the first time and it caused me to burn a pair of MOSFETs and forced me to redesign my half bridge layout.
Registered Member #4073
Joined: Sun Aug 28 2011, 08:43AM
Location: Australia
Posts: 17
Okay, thanks M.A.D. and Dr. Duck.
I was fairly sure it wouldnt be a problem, but I diddn't want to make another stupid mistake because I diddnt double check something (last time I wound a secondary at half the diameter by accident, making it un-useable for this design because it has a secondary resonance around 1MHz) and have to start again. I've paid colse attention the the length conductor around the half bridge, so stray inductance shouldn't cause too many problems.
I'll coat the coil with epoxy in the next day or two, and get the final bits and pieces together.
Something similar happened to me once. I was winding a secondary for SGTC and then the wire broke. I was pissed, but I just unwound everything and did everything again.
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Secondary coil - ran out of wire
