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Shoot-through 3 phase bridge? gate drive waveform
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ghoetic:

--- Quote from: duak on June 11, 2020, 02:45:11 am ---Ghoetic, have you considered the change that Yansi and I have suggested? (page 23 of the IRS2334 data sheet I referred to above.)
Infineon/IRF suggests Rvs not be greater than 5 ohms, I suppose to not affect gate drive.

Also, when I was looking for something else I found this on parasitic turning on: https://www.controleng.com/articles/tutorial-mitigating-parasitic-turn-on-effect-in-igbt-output-drives-to-improve-drive-performance/

Jon, I also worked with power FETs, but it was years ago.  I developed a 3 phase MOSFET servo amp in the mid to late 80s with a switching rate of 100 kHz.  MOSFETs at that time had bog slow body diodes so I had to isolate it with a Schottky rectifier and then add a fast recovery diode to handle the freewheeling current.  Fortunately Unitrode made a 50 ns, 50 A part but it was only available in a stud mount package.  I recall that the forward recovery time was doggone fast (<< 100 ns) and more of a function of the loop area and inductance.  If I remember my device physics correctly, an increased forward voltage simply causes the diode's depletion zone to close and conduct quicker.  Within a few years, similar parts were available in TO-247 style packages and a good bit of the series inductance went away.

I haven't designed with IGBTs.  I understand that they do not have body diodes as do MOSFETs, however they have other parasitic devices like a thyristor.  I wonder if the IGBTs that have anti-parallel diodes add another die to the package or do some sort of trick with a diode connected transistor hence the higher forward voltage drop?  Maybe it's just a smaller die that is optimized for speed and has a higher VF.

BTW, I tore down a 20 year old Mitsubishi VFD that had popped its IPM.  I wanted to see if I could convert it to generate a variable frequency PWM pulse train to drive an external H bridge for a single phase lab test source for the lab.  The potting compound was clear and I could clearly see the damaged IGBTs and that it had separate freewheeling diode dice.

Cheers,

--- End quote ---

Would need a greater load test before i make more charges.

As i posted above, i am up and running now with a motor https://youtu.be/SNKqk37RwU8
👍😊
nuno:
Locking the motor's rotor is a great load test. Your controller should survive that.
The "double pulse" test is an easy (usually non-destructive) test you can make to evaluate the "quality" of your power stage.
Especially with the shorter switching times you really need a good test setup (ground clips directly over the power devices pins, beware of where the GNDs of the several equipments are connected) to look at the waveforms around the power devices.
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