CT Ferrite toroids
Bud, Tue Jun 13 2017, 01:55PMHi all, I am looking for info on where to purchase good ferrite toroids to wind the CT's for my drsstc. The ones I am using now do not provide the correct output. I had set the OCD on the board to 3 volt limit on the bench and on the coil we see a much lower current limiting effect. These CT's are wound 2400:1 and have a 2 OHM resistor across which should output 2v at 2400 amp. I am seeing a limit of around 360 amp. I also have a ct wound for the scope and at limiting I only see 1.5 volts.
I have 3 sets of toroids......one for the feedback, one for the OCD, and one for the scope. This means the CT's are not working well for this machine. Does anyone info on good known ferrite toroids to use for this application.......where to buy and what to use?
First light test was done last night but I do not want to push things until I resolve the CT issue. Kinda like unprotected sex at his point!
Two years of work and I do not want to ruin it now.
Bud
Re: CT Ferrite toroids
Finn Hammer, Tue Jun 13 2017, 06:58PM
Bud,
I am pleased to see you use the spiral toroid.
I have used these ferrite toroids for all my coils over the years, and they work great for current monitoring, as well as gate drive.
Cheers, Finn Hammer
Finn Hammer, Tue Jun 13 2017, 06:58PM
Bud,
I am pleased to see you use the spiral toroid.
I have used these ferrite toroids for all my coils over the years, and they work great for current monitoring, as well as gate drive.
Cheers, Finn Hammer
Re: CT Ferrite toroids
Bud, Wed Jun 14 2017, 12:17PM
You were my inspiration to built the spiral toroid. As soon as I saw how you built it I knew I could reproduce it. It works really well.
Bud
Bud, Wed Jun 14 2017, 12:17PM
You were my inspiration to built the spiral toroid. As soon as I saw how you built it I knew I could reproduce it. It works really well.
Bud
Re: CT Ferrite toroids
Hydron, Wed Jun 14 2017, 08:35PM
I have used and can recommend B64290L0674X830 for gate drive transformers - very similar to what Finn suggested, just slightly larger.
That said, I don't think picking the very best ferrite is too critical for DRSSTC use - as long as you pick one with a reasonable Al value for the number of turns and frequency you'll probably be OK. With small burden resistors and big winding ratios, you're very unlikely to saturate anything, and I have gotten away with some crappy junk-box toroids in the past.
Hydron, Wed Jun 14 2017, 08:35PM
I have used and can recommend B64290L0674X830 for gate drive transformers - very similar to what Finn suggested, just slightly larger.
That said, I don't think picking the very best ferrite is too critical for DRSSTC use - as long as you pick one with a reasonable Al value for the number of turns and frequency you'll probably be OK. With small burden resistors and big winding ratios, you're very unlikely to saturate anything, and I have gotten away with some crappy junk-box toroids in the past.
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