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Voltage Runaway on Plane Power Alternator

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri May 08, 2009 6:17 am Post subject: Voltage Runaway on Plane Power Alternator

At 08:35 AM 5/8/2009, you wrote:

 	  Quote: 	
		  G'day Everyone,



I have a strange fault that has developed on my RV7, with Plane 

Power Internally regulated alternator.  I bought is as it has 

crowbar voltage protection built in.  The aircraft has 20 hours on 

it and up till recently the alternator worked fine.



The last two flights I have received Over Voltage alerts on takeoff 

from my EFIS and the 5A breaker has popped - so I guess the crowbar 

works as advertised and my avionics is all OK.  Resetting the 

breaker works fine once at pattern altitude and the prop is back to 

2500 RPM or so.  The unit then performs flawlessly for the rest of 

the flight.  I have not tried applying takeoff power at altitude, so 

I cannot be certain it is the high RPM causing it.



I called the guys at Plane Power and they suggested checking the 

field line and breaker which I will do tomorrow.  However, this is a 

pretty strange failure mode and I was wondering if anyone else on 

the list had any ideas.  I don't really want to risk cooking my 

radios etc.  There really is not much that can go wrong with the 

unit's wiring as it only has two wires connected to it.


	


   There is only one reason for an alternator to produce

   TOO MUCH voltage . . . serious fault in the regulator's

   ability to sense bus voltage -OR- some failure within

   the regulator's itty-bitty innards.



   It's unusual for an electronic failure on an integrated

   circuit to be intermittent/transient as you've described.

   But as you've observed, the ov protection system is ringing

   loud bells to let you know that the system needs some

   attention to details. It's unfortunate that you're so

   remote to the Plain Power facilities. If I were Plane

   Power, I'd want to get the unit back for inspection.



   I think it unlikely that "loose wiring" in the airplane

   would cause this, more likely that the problem is internal

   to the alternator. Work closely with Plane Power. They

   know more about their product than anybody else.

        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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frank.hinde(at)hp.com
Guest

Posted: Fri May 08, 2009 7:15 am Post subject: Voltage Runaway on Plane Power Alternator

Yes should be easy to check that you have the right field connections (make sure you cheeck of good crimps or soldered joints between the wires and the terminals connected to the alt..More than once I have pulled a wire clean out of a ring terminal bolted to the B post.



Make sure you have a good ground between the engine and -ve terminal to the battery...I assume your using the Plane power Cad plated brackets?...Because if you using painted brackets this can interrupt the ground between the alt case and the engine block..Ask me how I know...



But I agree with Bob, if you can't find a wiring fault I'd send it back to plane power.



Frank



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