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Alternator excitation - suggested wiring?

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mikefapex

Joined: 05 Jul 2007
Posts: 70
Location: Colorado

Posted: Thu May 14, 2009 8:12 am Post subject: Alternator excitation - suggested wiring?

I have a question about wiring my alternator. My question is primarily about the excitation/ignition-on connection. I've found lots of articles about alternators, and info on this list. But most other articles talk about internally regulated versions. So far I can't quite get my head about the excitation question.  I can surely experiment with the connections, and plan to do so this weekend. I'm just hoping to get a better understanding before diving in too deep with a running engine and spinning prop.



My alternator has three connections, one for field, one for 12v excitation, and the B lead. I have the B&C LR3C regulator, overall electrical is a Z19. The alternator was built by a local high performance shop, after talking through the needs of my aircraft. Good bearings and grease, precise tolerances, etc. All those things Bob talks about in his book. The instructions that came with it say:



"Alternator has isolated field wires. Either one can be the IGNITION ON 12 volt supply wire. The other  to the FIELD CONNECTION on the regulator. The regulator case must be grounded. "



So what I was planning to do is run a small wire from the B lead on the alternator to one of the alternator's connections, making it the IGNITION ON connection. Then connect the other tab to the Field connection on the regulator. That way when I turn on the Master Switch to middle position (batt) it sends 12 volts to the IGNITION ON connection.  The hope being that is supplies the alternator with that 12 volt IGNITION ON voltage.



I already know that turning the Master Switch to BATT position (or Alt) sends power all the way to the B lead.



What I am not sure about is: do I need to keep that excitation/Ignition on voltage running all the time the engine is running (would it hurt anything if I did)?  Or should it be shut off after the engine is started and alternator is producing power?



My Master Switch is exactly as in the Z19, so it controls the on/off of the regulator already.



It is this question of excitation that I am unclear about. Lots of articles talked about the need for an ignition on light as a mandatory component in making some alternators actually operate.



Thanks in advance,



Mike

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mikefapex

Joined: 05 Jul 2007
Posts: 70
Location: Colorado

Posted: Fri May 15, 2009 6:13 am Post subject: Re: Alternator excitation - suggested wiring?

Bob,



Thanks very much for that detailed explanation. That will help me plan this weekends activities.  



Mike

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mikef(at)apexconsultingse
Guest

Posted: Sun May 17, 2009 6:35 pm Post subject: Alternator excitation - suggested wiring?

Bob,



Thanks again for the information on regulators (pull up/pull down), and the way to wire it up. Sure feels good to have the system really working.� This list is great!



Mike



 On Sun, May 17, 2009 at 8:04 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

 

 --> AeroElectric-List message posted by: "mikef" <mikefapex(at)gmail.com (mikefapex(at)gmail.com)>

 

 

 Bob,

 

 

 I wanted to update you. After getting a new alternator plug that has the connections I needed, I experimented and rewired the field and ground leads per your suggestions.

 

 

 WhaLa, alternator started outputting about 15 volts. Too high, but a few turns of the LR3C regulator screw has it now outputing 14.2 volts. And if I move the Master Switch to BATT position the alternator stops producing voltage. Like Hannibal Smith always said: 'I love it when a plan comes together'.

  

 

 I have a Z19 system, and here are the measured voltages from various instruments/locations:

 

 Digital meter directly on the main battery: 14.23 v

 Digital meter on the Z23 field wire to cockpit: 1.90 v

 Digital panel Voltmeter on Ebus: 14.10 v

 EM2 engine monitor connected to main bus: 14.44 v

 

 

 Is that Z23/field voltage what you might expect?

 



  � Yes, depending on RPM and system loads, the

  � field excitation to the alternator can be quite

  � low. At low RPM and high loads, this reading

  � will climb until it reaches at or slightly

  � below bus voltage . . . this is were the alternator

  � is maxed out. A very low reading says the alternator

  � is carrying present loads without breaking a

  � sweat.

 

 

  � � � Bob . . .

 

  � � � ----------------------------------------)

  � � � ( . . . �a long habit of not thinking � )

  � � � ( a thing wrong, gives it a superficial )

  � � � ( appearance of being right . . . � � � )

  � � � ( � � � � � � � � � � � � � � � � � � � )

  � � � ( � � � � � � � � �-Thomas Paine 1776- �)

  � � � ----------------------------------------



 

 

 

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-- 

Mike



================================

Mike Fontenot

Apex Consulting & Services LLC

Lakewood, Colorado

303 / 731-6645

mikef AT apexconsultingservices DOT com

 =======

  [quote][b]

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