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Ducati regulator question

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Fri Jul 16, 2010 7:31 am Post subject: Ducati regulator question

I am building an RV-12.  Because I am registering as E-LSA, I must build it EXACTLY according to plans using the pre-assembled wiring harness and control board, essentially a plug and play system.  The schematic may be viewed here:

http://www.vansaircraft.com/pdf/revisions/RV-12/User_Manuals/MM-R1.pdf on page 173 of the 185 page of the Adobe document.

My question concerns the 22awg wire that connects the main bus to the "C" terminal of the Ducati voltage regulator.  First of all, there is no fuse protection for this 3-foot wire that passes through the firewall.  One half of the master switch is in series with this wire.  I thought the "C" terminal was for voltage sensing.  It seems that it is being used as an ON-OFF control for the regulator on the RV-12.  If terminal "C" really is a voltage-sense input, then it would seem that if the master switch were shut off while the engine was running, that the regulator would see a low input (0 volts) and put out a higher voltage, resulting in an over-voltage situation.  Another concern is the 22,000µf 25vdc capacitor on the control board which is on the cabin side of the firewall.  If the regulator fails and can not be shut off, an over-voltage situation could smoke the capacitor with no way to shut the power off to it.  So here are my questions:

Does terminal "C" of the Ducati regulator act as an ON-OFF control?

If the regulator fails and allows over-voltage, will opening input to terminal "C" shut off the regulator output?

Thanks,

Joe

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Joe Gores

jloram

Joined: 07 Nov 2009
Posts: 54
Location: United States

Posted: Fri Jul 16, 2010 10:38 am Post subject: Ducati regulator question

begin SPECULATION

While it may have a "sense" function, it is probably the power source for

the internal electronics. 

Without the source, the internal electronics won't startup, and the

regulator will remain dormant.

end SPECULATION



This configuration, with a motorcycle regulator, was used on the early

Jabiru engines and in that application powering the regulator without having

the engine running would burn out the regulator and the alternator.



-john- 



[quote] --

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 16, 2010 4:56 pm Post subject: Ducati regulator question

At 01:35 PM 7/16/2010, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "John Loram" <johnl(at)loram.org>



 begin SPECULATION

 While it may have a "sense" function, it is probably the power source for

 the internal electronics. 

 Without the source, the internal electronics won't startup, and the

 regulator will remain dormant.

 end SPECULATION 	


    Seems reasonable. Here's a schematic someone sent me of

    what was believed to be at least one version of a Ducati

    PM alternator rectifier/regulators. It's typical of

    many other diagrams I've seen:



  http://aeroelectric.com/Pictures/Regulators/regul_912.jpg



    The "C" lead is indeed a voltage sense lead. Further,

    it powers the regulation + SCR control circuits.  



 

  	  Quote: 	
		  This configuration, with a motorcycle regulator, was used on the early

 Jabiru engines and in that application powering the regulator without having

 the engine running would burn out the regulator and the alternator.



 	


    While this lead exercises ON/OFF control of the R/R, it's

    not in a position to do serious harm if left powered

    while the engine is not running. It's worst risk is

    that over a long period of time, it might run a battery

    down with what amounts to perhaps tens of milliamps

    of steady current draw.



  	  Quote: 	
		  > I am building an RV-12.  Because I am registering as E-LSA, I 

 > must build it EXACTLY according to plans using the 

 > pre-assembled wiring harness and control board, essentially a 

 > plug and play system.  The schematic may be viewed here:

 > http://tinyurl.com/2d4b9j8 

 > on page 173 of the 185 page of the Adobe document.

 > My question concerns the 22awg wire that connects the main 

 > bus to the "C" terminal of the Ducati voltage regulator.  

 > First of all, there is no fuse protection for this 3-foot 

 > wire that passes through the firewall. 	


    Yes . . . this is not in agreement with legacy esign

    goals for aircraft . . .



  	  Quote: 	
		  > One half of the 

 > master switch is in series with this wire.  I thought the "C" 

 > terminal was for voltage sensing.  It seems that it is being 

 > used as an ON-OFF control for the regulator on the RV-12.  If 

 > terminal "C" really is a voltage-sense input, then it would 

 > seem that if the master switch were shut off while the engine 

 > was running, that the regulator would see a low input (0 

 > volts) and put out a higher voltage, resulting in an 

 > over-voltage situation. 	


    You'd be correct if this were not ALSO a power supply

    wire for the R/R . . .



 

  	  Quote: 	
		   Another concern is the 22,000µf 

 > 25vdc capacitor on the control board which is on the cabin 

 > side of the firewall.  If the regulator fails and can not be 

 > shut off, an over-voltage situation could smoke the capacitor 

 > with no way to shut the power off to it. 	


    Also correct . . . 



 

  	  Quote: 	
		  > here are my questions:

 > Does terminal "C" of the Ducati regulator act as an ON-OFF control? 	


    Yes



  	  Quote: 	
		  > If the regulator fails and allows over-voltage, will opening 

 > input to terminal "C" shut off the regulator output? 	


    Very probably. Further, given that the output capability

    for the Rotax (and all PM) alternator is relatively low,

    the voltage is not going to climb precipitously . . .

    If you had an ACTIVE NOTIFICATION of high voltage, this

    would probably suffice to offer timely crew notification.



    Alternatively, you could add active OV protection like that

    illustrated in 



  http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z16M.pdf

 

    I would further suggest, active notification of low voltage

    is a good thing too.



    Finally, a 3A fuse in series with the "C" lead would be in

    conformity with legacy design goals.

 

   Bob . . .    [quote][b]

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Sat Jul 17, 2010 4:19 am Post subject: Re: Ducati regulator question

Bob & John,

Thanks for replying.  You answered my questions.  Now I have a better understanding of the Ducati regulator.

Joe

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