GDT Meltdown
orac12, Wed Apr 20 2016, 09:13PMAny thoughts as to why my GDT has got hot and melted the insulation, leading to shorted turns?
Its mounted to the IGBT heatsink, has rubber insulators, didnt think the heatsink would of got hot enough to do this. It seems to be mostly where the windings come out of the transformer and twisted together. Under the heatshrink where the leads come out, it seemed it had got hot in there as well.
Full bridge CM600's and 5 ohm gate resistors, 27V zeners back to back.
Re: GDT Meltdown
profdc9, Wed Apr 20 2016, 09:30PM
I don't have much experience with SSTC's but perhaps the toroid ferrite heated near its curie temperature, the magnetic permeability dropped, and the core saturated. Especially if the toroid is being heated by another device like the IGBT heatsink, or from hysteresis losses, it might not happen for awhile until the ferrite became hot enough.
Dan
profdc9, Wed Apr 20 2016, 09:30PM
I don't have much experience with SSTC's but perhaps the toroid ferrite heated near its curie temperature, the magnetic permeability dropped, and the core saturated. Especially if the toroid is being heated by another device like the IGBT heatsink, or from hysteresis losses, it might not happen for awhile until the ferrite became hot enough.
Dan
Re: GDT Meltdown
Goodchild, Thu Apr 21 2016, 01:37PM
I noted that only the striped conductors are melted, I'm assuming those are your primary. You likely don't have DC blocking on your primary GDT drive circuit. Without DC blocking high DC currents will flow in the primary causing it to heat up.
Goodchild, Thu Apr 21 2016, 01:37PM
I noted that only the striped conductors are melted, I'm assuming those are your primary. You likely don't have DC blocking on your primary GDT drive circuit. Without DC blocking high DC currents will flow in the primary causing it to heat up.
Re: GDT Meltdown
orac12, Thu Apr 21 2016, 08:04PM
Correct, the striped wires are the primary. Using the UD2.7c board, which has DC blocking caps on board.
orac12, Thu Apr 21 2016, 08:04PM
Correct, the striped wires are the primary. Using the UD2.7c board, which has DC blocking caps on board.
Re: GDT Meltdown
orac12, Fri Apr 22 2016, 11:42PM
Wound another one, don't seem to have any problems. Maybe I had it clamped up too tight and squashed some windings together / shorted them out.
orac12, Fri Apr 22 2016, 11:42PM
Wound another one, don't seem to have any problems. Maybe I had it clamped up too tight and squashed some windings together / shorted them out.
Re: GDT Meltdown
Justin, Sat Apr 23 2016, 03:24AM
Did you use a different core material by chance?
Justin, Sat Apr 23 2016, 03:24AM
orac12 wrote ...
Wound another one, don't seem to have any problems. Maybe I had it clamped up too tight and squashed some windings together / shorted them out.
Wound another one, don't seem to have any problems. Maybe I had it clamped up too tight and squashed some windings together / shorted them out.
Did you use a different core material by chance?
Re: GDT Meltdown
orac12, Sat Apr 23 2016, 03:52AM
Same core
orac12, Sat Apr 23 2016, 03:52AM
Same core
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