Friday, February 8, 2013

When FETs go bad

This has not been the winter for Inverters.  Yesterday I wanted to pump up the air compressor and blow out our small space heaters.  So I flipped on the appropriate breakers and switches and the compressor started to start, and then stopped.  I am guessing I had not payed attention to the water heater and block heater, both of which need to be turned off in order to allow enough power for the compressor 

Oh Weill  no worry.  That is what we have fuses for, right?   And yup - the control panel for the Heart 2.5kW inverter was dead - sounds like a blown master fuse.  Given it was late I put it off till this morning.

Well, when replacing the 300A class T fuse (the correct one one needs to use between a battery bank and large inverters) I had expected a little sparking - always is while the caps recharge, but this was a LOT of sparking.  So, before fully installing the new fuse I took off the cover of the inverter and . . .



Here is the FET driver board, with its rows of FETs (24 in this case).  Notice anything wrong?



How about this photo?  (See the cracked case)















Or, here or here....






Yup.  FETs are blown.   Sigh.  But that is OK as this happened before (in fact, it is how I got this inverter, free for the fixing).  And I carry spare FETs!



 Maybe this shows how overboard I am in the Spares department?  I carry spare FETs for our inverters...  Actually, they were left over from when I re-FETed the inverter the 1st time.  So, will just be a matter of getting out the soldering irons and working the magic.

Life will go on, inverters will be back on-line.  Great I am able to deal with this, but does also highlight the idea of KISS. . . .


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