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Thread: Alternator Field Switch

  1. #41
    59pacer's Avatar
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    Default Re: Alternator Field Switch

    With the engine stopped and the master and alternator switches on, how much current does the field circuit draw?

  2. #42
    CamTom12's Avatar
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    Default Re: Alternator Field Switch

    Quote Originally Posted by Gilbert Pierce View Post
    It depends on the alternator voltage regulator. Most automotive alternators with internal regulators have no over voltage protection (crowbar circuit). Alternators STCD for aircraft have over voltage protection. I am only familiar with the reset procedure on the Interav because I have one. Pulling the field circuit breaker on the Interav would reset the overvoltage circuit I believe.
    Ok. I've got a PlanePower 60A - I can't remember if it has overvoltage protection but I'm pretty sure it does. That's good to know, thanks!

  3. #43

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    Default Re: Alternator Field Switch

    Quote Originally Posted by 59pacer View Post
    With the engine stopped and the master and alternator switches on, how much current does the field circuit draw?
    I show a 3 amp draw with the alternator field switch on, and none with the field switch off.

  4. #44
    CamTom12's Avatar
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    Default Re: Alternator Field Switch

    Quote Originally Posted by SMO22 View Post
    I show a 3 amp draw with the alternator field switch on, and none with the field switch off.
    Mine agrees with you. First one is off, then on.




  5. #45

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    Default Re: Alternator Field Switch

    Good enough reason for me to keep the alt off while crranking it on coldays

  6. #46

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    Default Re: Alternator Field Switch

    My opinion is if having 3 amp to the regulator and the alternator drag affects starting it is time to check the wiring from the battery to the starter and the engine ground.
    Check the battery as well.


    Sent from my SM-N910V using Tapatalk

  7. #47

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    Default Re: Alternator Field Switch

    Probably not a big deal, but why waste energy?
    I chose to have a separate switch for the alternator so it is not an issue, the battery cranks to high heaven anyway, AGM 30ah 385cca a great battery.
    Last edited by SMO22; 02-10-2019 at 11:50 AM.

  8. #48
    CamTom12's Avatar
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    Default Re: Alternator Field Switch

    Yeah, Ive got enough cranking power I just leave the field CB on. I run an EarthX battery and a Skytec starter. Id almost bet I could taxi on the starter.

  9. #49

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    Default Re: Alternator Field Switch

    If it isn’t already that way, the aircraft could be wired to start with the master switch off. That way the only amps not going to the starter would be used to close the start solenoid.
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  10. #50
    Gilbert Pierce's Avatar
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    Default Re: Alternator Field Switch

    Quote Originally Posted by Jeff J View Post
    If it isn’t already that way, the aircraft could be wired to start with the master switch off. That way the only amps not going to the starter would be used to close the start solenoid.
    Mine is wired that way. It came from the factory that way.

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