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Capacitors keep blowing

in 912 / 914 Technical Questions 9 years ago
I have got a couple of friends who are in France at the moment and two have blown a capacitor within a couple of hours of each other, both on different aircraft. They have been replaced with new 22,000uf capacitors and one has blown again within a few minutes.
Has anyone, Rob, got any suggestions on what might cause this.
I have told them to check all the connections on the charging circuit which they spent the day doing yesterday, but altough everything looks ok, they have still blown.

Mark

  • Re: Capacitors keep blowing

    by » 9 years ago

    Hi Mark,

    A loose connection or a reversed polarity would cause this.
    A capacitor not rated for the proper heat range too. I have seen some use a capacitor only rated for 85C, but should be 105C. The 22K is a minimum and you can use a higher rated capacitor. Many now use a 33K or higher. If you don't like the spade connector type capacitor then the larger ones have screw terminals which are sturdier and more secure.
    I would think if they are blowing at startup or within a very short time I would look for some kind of short in a wire. Maybe a pinched wire grounding to metal somewhere?

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Capacitors keep blowing

    by » 9 years ago

    Are they sure they ordered 22,000uf or did they get 2,200uf by mistake?
    The battery is finding its main ground through the capacitor? check the battery ground strap for corrosion and security.
      
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  • Re: Capacitors keep blowing

    by » 9 years ago

    Check the voltage across the cap, and check the capacitor's voltage rating. Caps typically explode when their voltage limit has been exceeded...
      
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  • Re: Capacitors keep blowing

    by » 9 years ago

    Thank you chaps. I have a few things to check if they make it back. They have blown 5 capacitors now between 2 planes.

    I will report back when I get to see the aircraft.

    Cheers Mark
      
    Report

  • Re: Capacitors keep blowing

    by » 9 years ago

    Hi Mark,

    When you say blown does that mean it just quit working, got fried (melted) or actually blew apart?

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report
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