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Thread: Capacitor Wiring

  1. #1
    Agfoxflyer's Avatar
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    Default Capacitor Wiring

    This might be a dumb question, but I have asked the "Experts" at my home airport and got different answers. I believe that the Chevrons point to the positive side. But some say no negative. Any comments


    IMG_1878.jpg
    David E.
    Woodstock, Georgia
    N97DE S5 TD Flying

    N97KE RV-9A Sold
    N96KE RV10 Sold
    Rans S21 Helping Brother Build (Selling)
    Vans RV-14A (On Order)

  2. #2
    Senior Member Dave S's Avatar
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    Default Re: Capacitor Wiring

    agfox,

    This is one of those things you need to sure of in your own head....a person ends up buying more parts if it is connected the wrong way.

    Here is one reference on the subject of capacitor polarity ID.

    http://denethor.wlu.ca/common/capacitor_polarity.pdf

    Not saying I am an electrical engineer...however after studying the subject during my build I found that capacitors are generally marked (confusingly) in two ways. The logical one uses a "+" by the terminal which is supposed to be connected to the positive side of the system. The illogical one identifies the negative terminal which is suposed to be connected to negative side of the system with either an arrow or a series of chevrons pointing to the negative terminal up the side of the capacitor.

    FWIW - I connected the terminal with the chevrons pointing to it to the negative side of the system - been running flawlessly for 300 hours - no smoke or fires.

    To make it really confusing - some capacitors can be hooked up either way - the one used on Rotax Charging system is an electrolytic capacitor which has ony one right way.

    It's a variable marking system designed to confuse a person - so it's not a dumb question - it's a smart question - be sure you have it correct - one way it will work, the other way you will end up burning up some expensive parts.

    Sincerely,
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
    Senior Member Av8r_Sed's Avatar
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    Default Re: Capacitor Wiring

    As Dave surmised, polarity bar (Chevron stripe) is negative. Tie it to ground and you should be good to go.
    -- Paul S
    Model III SN910
    582 IVO Med

  4. #4
    Agfoxflyer's Avatar
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    Default Re: Capacitor Wiring

    Thanks Guys. Don't ask me how I know but if you connect wrong you get a loud bang, smoke, and oil dripping out of the thing.
    David E.
    Woodstock, Georgia
    N97DE S5 TD Flying

    N97KE RV-9A Sold
    N96KE RV10 Sold
    Rans S21 Helping Brother Build (Selling)
    Vans RV-14A (On Order)

  5. #5
    Senior Member t j's Avatar
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    Default Re: Capacitor Wiring

    Quote Originally Posted by Agfoxflyer View Post
    Thanks Guys. Don't ask me how I know but if you connect wrong you get a loud bang, smoke, and oil dripping out of the thing.
    ...and it stinks like crazy too.
    Tom Jones
    Classic 4 builder

  6. #6
    Agfoxflyer's Avatar
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    Default Re: Capacitor Wiring

    Wired it up. Flipped switches. No pop, smoke, oil, or smell. Good to go!
    David E.
    Woodstock, Georgia
    N97DE S5 TD Flying

    N97KE RV-9A Sold
    N96KE RV10 Sold
    Rans S21 Helping Brother Build (Selling)
    Vans RV-14A (On Order)

  7. #7
    Senior Member TJay's Avatar
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    Default Re: Capacitor Wiring

    What are they used for on a Kitfox?

  8. #8
    Senior Member Av8r_Sed's Avatar
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    Default Re: Capacitor Wiring

    In our charging systems, the stator produces AC output which goes to the regulator/rectifier. The ouput of that is DC plus an AC voltage on top of it. A capacitor is often used to filter out higher frequency AC ripple on the rectified DC supply. It helps keep the electronics happy and audio quiet.
    -- Paul S
    Model III SN910
    582 IVO Med

  9. #9
    Senior Member TJay's Avatar
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    Default Re: Capacitor Wiring

    Quote Originally Posted by Av8r_Sed View Post
    In our charging systems, the stator produces AC output which goes to the regulator/rectifier. The ouput of that is DC plus an AC voltage on top of it. A capacitor is often used to filter out higher frequency AC ripple on the rectified DC supply. It helps keep the electronics happy and audio quiet.
    Thanks, I was thinking to myself, there really cant be much on a kitfox that pulls enough power on start up that you to need the extra stored power of a capacitor but if it acts as a filter too that makes more sense.

  10. #10
    Senior Member TJay's Avatar
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    Default Re: Capacitor Wiring

    So how do you wire these things up, Do you run the hot wire to the positive side then continue from the positive side to the electronics buss? And ground side to ground, or does power go in one side and come out the other?

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