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Registered Member #9879
Joined: Tue Jan 29 2013, 05:00AM
Location: New Zealand
Posts: 37
Any 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.
Registered Member #58522
Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50
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.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
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.
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GDT Meltdown
