Electronics > Projects, Designs, and Technical Stuff
Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]
magic:
Are both FETs still driven from two opposite windings of the same GDT? This oscillation waveform makes no sense to me :-//
Refrigerator:
--- Quote from: magic on August 17, 2019, 06:14:07 am ---Are both FETs still driven from two opposite windings of the same GDT? This oscillation waveform makes no sense to me :-//
--- End quote ---
The GDT has two isolated outputs, both of which are inverted.
Refrigerator:
I got it to make a few snotty welds before it died (i died a little inside too) but all is not lost.
Turns out the low side gate discharge transistor shorted out and prevented the low side MOSFETs from turning on.
Since i'm all out of suitable PNP transistors i redesigned the gate discharge to be handled with a NPN transistor.
I basically flipped the PNP circuit over and put an NPN transistor instead of the PNP transistor, confirmed that they both work identically with Ltspice.
Now all that is left to do is to make a new MOSFET board.
So far all the testing was done without gas, because i don't have any at the moment and also my current sensing circuit needs some tweaking.
tautech:
Get some gasless wire.
Refrigerator:
Previously i had a pair of SS8550 transistors, one per side.
The collector of the SS8550 shorted to the emitter but the base seems fine so i assume the collector current was too high.
The MOSFET board was made for one MOSFET per side but i added two more so i guess discharging both gates at once was a little too much to ask, even if the transistor is rated for 1.5A.
All MOSFETs had a 10Ω resistor on the gate.
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