Hi,
I'm reopening this topic.
I tested KOA HPC3 ceramic resistors and unfortunately they are dangerous to be used as a replacement of the thick film resistors proviously used in the device. When there is a short circuit in the device (inverter)
Ah, so it's incorrectly designed in general. It's not the resistor's fault at all. The design itself needs to be fixed.
It's sadly an all too common oversight, to employ a precharge circuit, and stop short of adding a voltage threshold and timeout to protect it. Common result, resistor stuck on into shorted load, pffst-bang, whole thing's cacked. Maybe just the resistor fails (fusible), maybe it melts and failure cascades.
A notable example I saw from a friend, a hi-fi audio amp used a wirewound resistor for this. When the outputs failed shorted, the precharge dutifully turned on and stayed on, glowing red hot for, probably some minutes. Now, this resistor was installed above the main PCB, so, it wasn't a pretty sight. Smoke must've been pouring out of the poor thing before the user noticed it wasn't working. I can only begin to imagine the smell... trying to clean that out is at least as bad as cigarette smell.
The board ended up serviceable, I think it was, no traces or components in the blackened area, but man... YUCK!
Tim