Author Topic: Help with mosfet replacement in UPS  (Read 494 times)

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Offline benzi

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  • Country: pl
Help with mosfet replacement in UPS
« on: April 20, 2020, 12:19:07 pm »
Hello!
I'll be upfront and admit I'm probably just a noob.

During maintenance I did an oopsie and I've blown up mosfets in UPS APC SUA1500RMI2U. Upon visual inspection boards seem fine except blown mosfet I've identified as Fairchild Semiconductors HRF3205.
Now, going with assumption of me being an idiot and improperly powering on the UPS or not noticing I've shorted something being the failure mode I'd like to ask about replacement part.

Looking at similar parameters and local availability I've found IRF3205PBF being quite similar to HRF3205, however with some discrepancies. Here's comparison link to Digikey for your convenience https://www.digikey.com/short/zp01vp
My questions are:
- Are differences in Gate Charge (146nC @ 10V vs 170nC @ 10V ) and Input Capacitance (3247pF @ 25V vs 4000pF @ 25V) going to cause problems in long term operations?
- I presume higher drain current is not an issue, is that right?
- Is there something in datasheet staring at me and saying that this is bad idea?
 

Offline keymaster

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  • Country: gr
Re: Help with mosfet replacement in UPS
« Reply #1 on: April 20, 2020, 03:02:39 pm »
the IRF3205PBF  is better (not by much ).
the differences in  Gate Charge and Input Capacitance , makes it , easier to drive the mosfet.
the drain current is the limit , so no problem there either .

there is always the possibility that the controller of the mosfet is dead too.
look also for short diodes .
 
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Offline MarcosL

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Re: Help with mosfet replacement in UPS
« Reply #2 on: February 19, 2021, 07:30:36 am »
I am in the exact same situation, my ups also blew an HRF3205. Did your fix work? Did you have any other problems if/when you swapped the part out?

Also, my UPS (BE500U) failed due to repeated on-off cycles from blackouts. All that was plugged in was a consumer grande Asus router.
 

Offline MarcosL

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  • Posts: 2
  • Country: us
Re: Help with mosfet replacement in UPS
« Reply #3 on: April 21, 2021, 02:08:59 am »
Wanted to give an update that just replacing the MOSFET did not work. I am sure other stuff had failed as well but it was not worth fixing at that point.
 


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