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Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
I'm working on the power supply for a laser project of mine. I wound a 1315 turn primary, with two layers of paper, superglued in place between the layers, and when winding I brought the end of each layer back to the beginning of the last and carried on winding. I then held the coil under vacuum in oil for an hour, but once rigged up to my half bridge with 250 watts in at 70 volts the sparks were pretty pathetic and the coil shorted out under the oil through the top layer of insulation. The small arcs make me thing that there may have been an internal short in the first place, has anyone got any experience with winding flyback secondaries? I'm aiming for 15kv at 20mA
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
your info could be organized. specify: primary max voltage primary turns secondary max voltage secondary turns a dimensional dwg from your magnetic core
primary and secondary coils sketch also
secondary coil fist tryal sketch a coil as: 1320 turns in 20 layers 66 turns per layer kraft paper 0.2mm thick (or 2 x 0.1mm) between the layers kraft paper with 10mm margens, one each side of wire. Then check if the coil fit in the core.
so the voltage between 2 adjacent turns may be 1.41 x 15000/1320 = 16V the voltage from each layer may be 1056 volts and max voltage between two adjacent layer may reach 2112V 0,2mm kraft paper imerse in oil is good for 2500V if no air bubles
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Hi HDF49, I think I can help you out.
First of take a look here and here
Both flybacks are using the same core and are insulted with 2 layers of overhead projection sheets that are submerged in mineral oil. (not put under a vacuum, which would greatly improve the lifespan). I have recently made two "dry" flybacks both with 2 layers of the projection sheets, and they have a very nice output at 40v in and no corona what so ever.
Since homemade flybacks usually have a high amp output it is better to use thinner wire, I like to use 32 awg for flybacks, It gives it the same characteristics of a factory made one at high turns like(2500+) meaning it doesn't melt metal instantly but can still melt steal if the arc is held for a couple seconds.
Make your layer or insulation as wide as for coil form is.
Hope this helps
Im having trouble upload a picture to this thread, i will try again later
Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
Ok thanks for the help guys, I think I'm going to take the top layer of turns off and add a lot more insulation on top to stop the same again. I've submerged it in a mineral gear box oil, did you use a proper insulative oil? If all else fails I'll buy some overhead transparencies, and possibly make a zvs driver for more current. I'm ust very annoyed as it was my last spool of wire!
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
HDF49 wrote ...
Ok thanks for the help guys, I think I'm going to take the top layer of turns off and add a lot more insulation on top to stop the same again. I've submerged it in a mineral gear box oil, did you use a proper insulative oil? If all else fails I'll buy some overhead transparencies, and possibly make a zvs driver for more current. I'm ust very annoyed as it was my last spool of wire!
Yea, i use mineral oil. it works really well and is pretty cheap. You can get it at most stores.
You also wont see very impressive results without a zvs or some kind of half bridge driver, What driver are you using?
Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
A half bridge of irfp260s, I'm having variac trouble at the moment too so I need to sort out my power supply. I think I might make a zvs driver, less to go wrong, the oscillator of my half bridge section is giving me grief again!
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