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Power Mosfets

Tonyf

Hi, I’m new to the forum I’m an electronics engineer and I hope I can contribute to the forum in the future.

at the moment I have a question about mosfets which I know little about.


I have an inverter using 104R5NT Mosfets.

The inverter uses 16 of these Mosfets and 4 of these have exploded. The Inverter still works.

im struggling to find replacements for these Mosfets.

Im wondering whether I could replace the broken ones with a similar, but not the same Mosfet or indeed whether I should replace all of the Mosfets.

Has anyone had a similar problem or better knowledge of mosfets?

Tony

  • Hi Tony,

    It's hard to be sure without knowing how the circuit used them, but I can't imagine they are matched parts, they seem like low-cost MOSFETs. It could be good to just replace what is blown, and see if that works.

    However, it would also be good to (mentally) explore why they got damaged if you have not already done so, e.g. is the load wrong for the use-case that the device is designed for, or is an unusual load being attached while the inverter is running (worth checking the user manual if that is inadvisable or not), or is it running in temperature extremes, and so on. It might not be possible to be sure of the cause of course.

  • I've had problems with large MOSFETs not being able to handle large inrush current, which is typical of inverters. My solution at the time was to use FETs with much higher current ratings. I'm not sure if lower on-resistance is better, since the on-resistance can help limit in-rush current. But with higher resistance, they will get hotter. You might want to measure the FET temperature to see if the heatsinks are adequate.