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L-40 Alternator Output

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markn(at)fuse.net
Guest

Posted: Tue May 30, 2006 1:51 pm Post subject: L-40 Alternator Output

I am using B&C's L-40 alternator and have just completed the 40 hour Phase 1

flight testing. Now that I am considering night flight, I have begun testing

my lighting system.



I noticed that turning all electrical equipment (Nav, landing, panel lights,

pitot heat and radios) puts a draw of about -15 amps on the ammeter at 1500

RPM. I did a load analysis earlier and I calculated full system load is 34

amps.



Is this just a simple case of alternator overload or could there be

something else?  I put in the alt field test point as The Aeroelectric

Connection suggests. At full load, the field voltage is changing between 11

and 12 volts. I would conclude from this that the alternator is putting out

everything it has but I'm still at a deficit.



Is this alternator really able to put out the full 40 amps as advertised, or

am I just drawing more power than calculated?



Any suggestions on a 60-80 amp automotive alternator with external

regulation?



Mark Neubauer

(513) 583-1222

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mstewart(at)iss.net
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Posted: Tue May 30, 2006 2:31 pm Post subject: L-40 Alternator Output

Mark hows your system voltage while at a cruise rpm?

Mike

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markacarey(at)msn.com
Guest

Posted: Tue May 30, 2006 6:49 pm Post subject: L-40 Alternator Output

 	  Quote: 	
		  From what I understand there is a considerable variation with RPM.  For 

instance the 20 AMP B&C only puts out 12 amps at 2000 but it generates 18 at 
	


2500.  My approach is to install the 40 as a primary and use the 20 in place 

of the vacuum pump for night approaches if needed (or rely on the battery 

for a short time).  The pitot is a big draw that is likely a rare need at 

night.

[quote]From: "Stewart, Michael (ISS Atlanta)" <mstewart(at)iss.net>

Reply-To: aeroelectric-list(at)matronics.com

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

Subject: RE: L-40 Alternator Output

Date: Tue, 30 May 2006 18:05:40 -0400




<mstewart(at)iss.net>



Mark hows your system voltage while at a cruise rpm?

Mike

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nuckollsr(at)cox.net
Guest

Posted: Wed May 31, 2006 5:19 am Post subject: L-40 Alternator Output

At 07:44 PM 5/30/2006 -0700, you wrote:



 	  Quote: 	
		  



 >From what I understand there is a considerable variation with RPM.  For

instance the 20 AMP B&C only puts out 12 amps at 2000 but it generates 18 at

2500.  My approach is to install the 40 as a primary and use the 20 in place

of the vacuum pump for night approaches if needed (or rely on the battery

for a short time).  The pitot is a big draw that is likely a rare need at

night.


	


    The stated RPM vs. OUTPUT values are for alternator RPM, not

    engine RPM. If you're mounted on a Lycoming with about 4:1

    pulley ratio, you should be able to get full output from

    any alternator at anything higher than taxi RPM on engine.



    You need to conduct some data measurements per Note 8 of:



http://aeroelectric.com/articles/Rev11/AppZ_R11G.pdf



    And get back to us. In particular, we need to know the field

    voltage and bus voltage when you're experiencing the "insufficient

    output" condition noted in your first posting. The need for

    knowing field voltage as a diagnostic tool was the reason

    for crafting Z-23 in the Z-figures.



    Bob . . .

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