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Alt field ckt breaker tripping

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jpkarnes

Joined: 03 Jul 2011
Posts: 19

Posted: Mon Aug 12, 2013 3:26 pm Post subject: Alt field ckt breaker tripping

My 5 amp alternator field circuit breaker is tripping after the engine runs for about a minute.  I removed the alternator and had it evaluated (at) the local auto parts store and it checked out OK.  What other causes other than an overvoltage condition could cause this to happen?  The alternator is a Mitsubishi internally regulated variety.  The system is fashioned on the "general aviation" schematic in the Aeroelectric appendix.  I just completed an upgrade to include a secondary ignition setup with a switch to select the primary/secondary ignition.  The engine is an EA-81 Stratus Subaru engine on a Zenith 601 HDS.



 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Aug 12, 2013 7:33 pm Post subject: Alt field ckt breaker tripping

At 06:25 PM 8/12/2013, you wrote:



 	  Quote: 	
		  My 5 amp alternator field circuit breaker is tripping after the 

engine runs for about a minute.  I removed the alternator and had it 

evaluated (at) the local auto parts store and it checked out OK.  What 

other causes other than an overvoltage condition could cause this to 

happen?  The alternator is a Mitsubishi internally regulated 

variety.  The system is fashioned on the "general aviation" 

schematic in the Aeroelectric appendix.  I just completed an upgrade 

to include a secondary ignition setup with a switch to select the 

primary/secondary ignition.  The engine is an EA-81 Stratus Subaru 

engine on a Zenith 601 HDS.


	


    Has the airplane flown? Has the system operated as

    expected in the past but shows a new symptom?

    Most alternators with built in regulators are not

    strictly compatible with the crowbar ov module

    sold by B&C and myself.



    The 5A field breaker needs to have ABSOLUTE control

    over field excitation voltage. This generally

    accomplished by some modification of the alternator's

    internal wiring . . . like a PlanePower, or modified

    for external regulation like B&C.



    This does not explain the symptoms you're seeing.

    I didn't fine your email address in my sales records

    which suggests you got the OVM from B&C.



    If you like, you can send me the OVM and I'll make

    sure it's calibrated correctly. This is the first

    step toward understanding root cause for the trips.

    How old is your battery and what size?



   Bob . . .

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user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Tue Aug 13, 2013 5:32 am Post subject: Re: Alt field ckt breaker tripping

 	  Quote: 	
		  My 5 amp alternator field circuit breaker is tripping after the engine runs for about a minute. I removed the alternator and had it evaluated (at) the local auto parts store and it checked out OK. What other causes other than an overvoltage condition could cause this to happen? 	


1. A wire shorting to ground could trip the breaker.

2. The overvoltage module might be set for the wrong voltage, thus tripping the circuit breaker at normal voltages.

3. There could be high resistance in the alternator field circuit.  This makes the voltage regulator see a lower voltage than exists on the main bus.  The voltage regulator then puts out higher current in order to increase the alternator output voltage.

4. The voltage regulator could be defective.

5. The circuit breaker could be getting warm from a bad connection.

6. The circuit breaker could be defective.



Number 3 above is the most likely cause of the problem.  Every switch and terminal connection is suspect.  A combination of borderline connections can add up their resistances to cause a lower voltage at the regulator.

Joe

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_________________
Joe Gores

mrspudandcompany(at)veriz
Guest

Posted: Tue Aug 13, 2013 6:58 am Post subject: Alt field ckt breaker tripping

 	  Quote: 	
		  > My 5 amp alternator field circuit breaker is tripping after the engine 

> runs for about a minute. I removed the alternator and had it evaluated (at) 

> the local auto parts store and it checked out OK. What other causes other 

> than an overvoltage condition could cause this to happen?



 1. A wire shorting to ground could trip the breaker.

 2. The overvoltage module might be set for the wrong voltage, thus 

 tripping the circuit breaker at normal voltages.

 3. There could be high resistance in the alternator field circuit.  This 

 makes the voltage regulator see a lower voltage than exists on the main 

 bus.  The voltage regulator then puts out higher current in order to 

 increase the alternator output voltage.

 4. The voltage regulator could be defective.

 5. The circuit breaker could be getting warm from a bad connection.

 6. The circuit breaker could be defective.



 Number 3 above is the most likely cause of the problem.  Every switch and 

 terminal connection is suspect.  A combination of borderline connections 

 can add up their resistances to cause a lower voltage at the regulator.


	




        This line was in the original post:



       " The alternator is a Mitsubishi internally regulated

        variety."



        This may have a substantial effect on the operation,

        as per Bob's previous posting.



        Roger 

--



Do you have a slow PC? Try a Free scan http://www.spamfighter.com/SLOW-PCfighter?cid=sigen

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jpkarnes

Joined: 03 Jul 2011
Posts: 19

Posted: Tue Aug 13, 2013 9:42 am Post subject: Alt field ckt breaker tripping

Hi all, 

  

The engine and its electrical system has flown for over 100 hours.  The battery is a brand new 12V 18AH gel battery.  The plane has not flown for over a year while some modifications/upgrades have been undertaken.  The only difference is the installation of a secondary ignition system ala Paul Messenger's dual dizzy setup.   I really doubt that there is a short to ground that is causing this problem.  Do you recommend installing an external voltage regulator and if so, which one?  Clearing this latest hurdle is the only thing keeping me from getting airborne again. ) 

  

John Karnes 

Suquamish, WA

 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 14, 2013 8:23 am Post subject: Alt field ckt breaker tripping

At 12:40 PM 8/13/2013, you wrote:



 	  Quote: 	
		  Hi all,



The engine and its electrical system has flown for over 100 

hours.  The battery is a brand new 12V 18AH gel battery.  The plane 

has not flown for over a year while some modifications/upgrades have 

been undertaken.  The only difference is the installation of a 

secondary ignition system ala Paul Messenger's dual dizzy setup.   I 

really doubt that there is a short to ground that is causing this 

problem.  Do you recommend installing an external voltage regulator 

and if so, which one?  Clearing this latest hurdle is the only thing 

keeping me from getting airborne again. )


	


   Okay, good data. We know this is a change from previously

   satisfactory operation. The battery is relatively new

   and not likely to be 'soggy' such that it contributes

   to system instability.



   A automotive shop has pronounced the alternator as

   righteous so it seems there is little probability

   of internal regulator failure. You can confirm by

   running the airplane with a voltmeter on the bus

   (preferably an analog meter with a needle) and

   see that the voltage is not only in the ballpark

   but not 'jumpy'. Of course, you need to disconnect

   the OV module.



   Once you have confidence in alternator performance

   then attention turns to the ov module. It may well

   be out of calibration. You can test it on the bench

   with an adjustable power supply. If a current limited

   supply, set for about 1A, if not, put an automotive tail

   light bulb in series with the ov module.



   Increase voltage very slowly until the voltage drops and/or

   light bulb lights. The module should trip at more than 16.0

   and less than 16.5 volts.



   I wouldn't worry about flying without it. Using the crowbar

   OV module on an internally regulated alternator offers

   a false sense of security. There are failures internal

   to the regulator that cannot be externally address

   except with techniques like . . .



http://tinyurl.com/7z6yzv9



   There are dozens of suitable regulators for external

   control of an alternator. The problem is that you need

   to open your alternator, ground one field brush, bring

   other brush to outside world.



   Let's get your airplane flying first and then talk

   about how you're going to address over-voltage

   events.

   Bob . . .

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jpkarnes

Joined: 03 Jul 2011
Posts: 19

Posted: Wed Aug 14, 2013 8:27 am Post subject: Alt field ckt breaker tripping

    The 5A field breaker needs to have ABSOLUTE control 

    over field excitation voltage. This generally 

    accomplished by some modification of the alternator's 

    internal wiring . . . like a PlanePower, or modified 

    for external regulation like B&C. 



How do I achieve the state you describe above "ABSOLUTE control over field excitation voltage."



    This does not explain the symptoms you're seeing. 

    I didn't fine your email address in my sales records 

    which suggests you got the OVM from B&C. 



I think I purchased the OVM from you; it was probably over 10 years ago...



    If you like, you can send me the OVM and I'll make 

    sure it's calibrated correctly. This is the first 

    step toward understanding root cause for the trips. 

    How old is your battery and what size? 



Battery is 12V 18AH gel battery...



Thanks so much for your help!!



John K.

Zenith 601HDS with Stratus Subaru engine

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jpkarnes

Joined: 03 Jul 2011
Posts: 19

Posted: Wed Aug 14, 2013 10:56 am Post subject: Alt field ckt breaker tripping

Bob, you made my day.  The engine has never run better and I have adhered to just about every recommendation you gave in your manual.  I am an electrical neophyte and your input has been invaluable.  I owe you a debt of gratitude!! 

  

John K. 

Suquamish, WA 

Zenith 601HDS w/Stratus Subaru/Ram heads

 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 14, 2013 3:08 pm Post subject: Alt field ckt breaker tripping

At 01:55 PM 8/14/2013, you wrote:



 	  Quote: 	
		  Bob, you made my day.  The engine has never run better and I have 

adhered to just about every recommendation you gave in your 

manual.  I am an electrical neophyte and your input has been 

invaluable.  I owe you a debt of gratitude!!



  '


	


   Pleased to be of service. Fly comfortably . . .



   Bob . . .

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