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912S External Alternator Question

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CDE2fly(at)aol.com
Guest

Posted: Sat May 30, 2009 11:05 am Post subject: 912S External Alternator Question

Just completed the first start on a 912S and all went well except the Rotax  external 40 amp alternator is not providing any power (I have the internal  alternator from the engine switched off while checking the external  alternator).  I currently just run a wire from the output stud on the  alternator to the power buss.  I'm thinking that I also need to run a wire  from the faston connection on the rear of the alternator to the postive battery  post.  I believe this is how the alternator senses low voltage in the  battery and allows the regulator to send power to the alternator out put  stud.  Can any one confirm?

  

 Thanks!

  

 Chris

 Kitfox 7 (99% Complete)

 Rotax 912S

 A Good Credit Score is0x1201367186/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=62%26bcd=MaystepsfooterNO62>See yours in just 2 easy steps!

  [quote][b]

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lcfitt(at)sbcglobal.net
Guest

Posted: Sun May 31, 2009 8:54 am Post subject: 912S External Alternator Question

Chris,



I am definitely not an expert on alternators, but it is my understanding 

that if you simply switch the internal "alternator" turned off without some 

load across the output leads of the regulator, you can fry the regulator. 

If it is swithched off between the coils and the regulator - no problem.



Others with more understanding will no doubt chime in, but a true alternator 

needs voltage from the battery to energise the field winding, otherwise all 

you have is a bunch of wires spinning.



Lowell



---

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CDE2fly(at)aol.com
Guest

Posted: Sun May 31, 2009 6:44 pm Post subject: 912S External Alternator Question

Thanks for the advice Lowell.  I'll rearrange things to send the  internal amp power to the switch first then to the regulator.  I think  you're right about the alternator needing voltage the battery.  I'll check  with Lockwood tomorrow and 

  

  In a message dated 5/31/2009 12:54:57 P.M. Eastern Daylight Time,  lcfitt(at)sbcglobal.net writes:

  	  Quote: 	
		  -->    Kitfox-List message posted by: "Lowell Fitt"    <lcfitt(at)sbcglobal.net>



Chris,



I am definitely not an    expert on alternators, but it is my understanding 

that if you simply    switch the internal "alternator" turned off without some 

load across the    output leads of the regulator, you can fry the regulator. 

If it is    swithched off between the coils and the regulator - no problem.



Others    with more understanding will no doubt chime in, but a true alternator    

needs voltage from the battery to energise the field winding, otherwise    all 

you have is a bunch of wires spinning.



Lowell



-----    Original Message ----- 

From: <CDE2fly(at)aol.com>

To:    <kitfox-list(at)matronics.com>

Sent: Saturday, May 30, 2009 11:59    AM

Subject: 912S External Alternator Question

 	  Quote: 	
		      Just completed the first start on a 912S and all went well except the 

    Rotax

 external 40 amp alternator is not providing any power (I have    the internal

 alternator from the engine switched off while checking    the external

 alternator).  I currently just run a wire from the    output stud on the 

 alternator

 to the power buss.  I'm    thinking that I also need to run a wire  from the

 faston    connection on the rear of the alternator to the postive battery 

    post.

 I believe this is how the alternator senses low voltage in    the  battery

 and allows the regulator to send power to the    alternator out put  stud. 

 Can

 any one    confirm?



 Thanks!



 Chris

 Kitfox 7 (99%    Complete)

 Rotax 912S

 **************A Good Credit Score is 700    or Above. See yours in just 2 

 easy

 steps!

    MaystepsfooterNO62)

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 An Excellent Credit Score is 750. See Yours in Just 2 Easy Steps!

  [quote][b]

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Jun 01, 2009 7:49 am Post subject: 912S External Alternator Question

That all depends on whether you alternator has field coils or a permanent magnet.  The one with the field coils the voltage regulator adjusts the power going to the field coils thus adjusting the voltage of the alternator output.  The permanent magnet alternator tries to produce as much power as it possibly can.  The –power produced is then sent to a circuit which directly regulates or stabilizes the power produced.   

   

Generally the field coil alternators produce DC because the rectifier plates are built into the  alternator itself.  The permanent magnet types I’ve seen do not have the rectifier plates built in.  Rectification   ( changing from AC to DC) is done after voltage stabilization.  

   

Noel  

       

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of CDE2fly(at)aol.com

 Sent: 01 June 2009 12:02 AM

 To: kitfox-list(at)matronics.com

 Subject: Re: 912S External Alternator Question  

  

  

     

Thanks for the advice Lowell.  I'll rearrange things to send the internal amp power to the switch first then to the regulator.  I think you're right about the alternator needing voltage the battery.  I'll check with Lockwood tomorrow and   

    

   

      

In a message dated 5/31/2009 12:54:57 P.M. Eastern Daylight Time, lcfitt(at)sbcglobal.net writes:  

  [quote]  

--> Kitfox-List message posted by: "Lowell Fitt" <lcfitt(at)sbcglobal.net>

 

 Chris,

 

 I am definitely not an expert on alternators, but it is my understanding 

 that if you simply switch the internal "alternator" turned off without some 

 load across the output leads of the regulator, you can fry the regulator. 

 If it is swithched off between the coils and the regulator - no problem.

 

 Others with more understanding will no doubt chime in, but a true alternator 

 needs voltage from the battery to energise the field winding, otherwise all 

 you have is a bunch of wires spinning.

 

 Lowell

 

 ---

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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