I wasn't there. If your design involves large bus capacitors, there's still a "chance" to damage the IGBTs with floating gate inputs, despite of current limiting. At worst case, the full capacitor energy can have discharged to a desaturated IGBT. Also ESD induced gate overvoltage can permanently damage the device.Increasing gradually the loading current, the current limiter of our dc supply limited the current and we had to stop to
increase the limit. After this, the switch remained at this state, and the dc bus is short-circuited.
Thank you for your replies!
@Tahmid
The evaluation board from the manufacturer I suppose that provides this resistor. However, I tried the resistor
when the IGBTs were not supplied with control and power input, and the IGBTs still remain short-circuited.
I presume, that you have the gates shorted to emitter by a resistor (or a wire) now. Otherwise, the measurement would be meaningless.Ok I measured the resistances...
I already told, how you can easily manage to destroy the IGBTs, even with current limited supply:I believe that we took all the means of protection. Rated characteristics are 1000V, 200A and the experiment was of about
200V and 10A (current limiter). Have you any idea what caused the problem?
I presume, that you have the gates shorted to emitter by a resistor (or a wire) now. Otherwise, the measurement would be meaningless.
I already told, how you can easily manage to destroy the IGBTs, even with current limited supply:
- By operating the IGBTs in linear (desaturated) region, either by floating gates or incorrect gate drive
This is right but how to protect the other IGBTs for this situation?- In addition, it's possible by drawing excessive overcurrents from bus capcitors by switching to an output or bridge short
As you reported about floating gate operation, I have no difficulties to imagine, how.
An IGBT or IGBT module with floating gate input may be easily damaged from ESD events and also possibly go to low resistance without connecting a gate driver. If connecting a power supply with sufficient current capability, the IGBTs can be permanently damaged.
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