November 19, 20241 yr I have a 3kva must inverter with error code 09, I checked and found out all DC-DC mosfets blown, I replaced them and made sure all the components are okay. Now the problem is the inverter is not turning on with the mosfets replaced but if I remove them it turns on, If I measure the frequency voltage it's normal and balanced at 5.1v .Kindly assist where I am getting it wrong, thanks.
November 19, 20241 yr 2 hours ago, Binus said: all DC-DC mosfets blown, I replaced them and made sure all the components are okay. I assume you mean that you checked all the diodes, transistors, resistors, and zeners in the MOSFET driver circuit. Perhaps the SG3525 or its power supply, or near components? What about the small (TO-92) MOSFETs that seem to be for turning off the main MOSFET gate drive? 2 hours ago, Binus said: Now the problem is the inverter is not turning on with the mosfets replaced but if I remove them it turns on, That's weird. Have you checked the DC-DC IGBTs at the high voltage end? It sounds to me like maybe an upper and lower pair are turning on and shorting the DC bus. Maybe. 2 hours ago, Binus said: If I measure the frequency voltage it's normal and balanced at 5.1v . Sorry, I just can't understand that. What exactly are you measuring here? Power supply? Gate signals? The gate signals should be switching from around -5.6 V to +13ish volts, when the DC-DC converter is enabled. Respect for getting the transformer unsoldered without completely butchering the PCB, on the top side at least.
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