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Rotax w/ Perihelion OVM

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rv8iator

Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR

Posted: Sun Mar 15, 2009 11:44 am Post subject: Rotax w/ Perihelion OVM

 	  Quote: 	
		   

Hello All... 

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />  

Attached is a PDF of Z-16 with the incorporation of Perihelion OVM into the electrical system for a Rotax powered KitFox. I am new to the Rotax.   

  

I purchased this to provide over voltage protection for the electrics powered by the built-in alternator on the Rotax.  I am not entirely clear on the operation of the Rotax alternator nor is the Rotax manual.  It contains only a schematic, no â€œtheory of operationâ€.  It has what appear to be two B leads.  Per Bobâ€™s schematic breaking one B lead shuts down the alternator. Per Rotax the output is 20A(at)5,000 RPM.  Thus a 20A relay would be suitable if each B lead produces 10A max.  Since Rotax calls the voltage regulator a rectifier/regulator I am assuming each B lead is single phase AC but I am not clear as to how breaking one B lead would shut down the alternator. 

  

My intent then is to switch the relay per Bobâ€™s Z-16 schematic using your OVM as opposed to the crowbar method. 

  

A couple of questions:  Why both a fusable link and 5A CB in series on the master sw/OV disconnect relay?  How does breaking one line from the 'dynamo' shut it down, or does it?  Per this schematic power is required from the battery to close the OV disconnect relay and bring the 'dynamo' on-line.  Thus with a dead battery there is no way to bring the 'dynamo' on-line? 

  

Thanks for your helpâ€¦ 

  

Chris Stone 

RV-8 wiring 

Kitfox-7 wiring

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_________________
C. Stone (RV8iator)

nuckolls.bob(at)aeroelect
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Posted: Sun Mar 15, 2009 12:20 pm Post subject: Rotax w/ Perihelion OVM

 	  Quote: 	
		    I purchased this to provide over voltage protection for the electrics powered by the built-in alternator on the Rotax.  I am not entirely clear on the operation of the Rotax alternator nor is the Rotax manual.  It contains only a schematic, no theory of operation.  It has what appear to be two B leads.  Per Bob's schematic breaking one B lead shuts down the alternator. Per Rotax the output is 20A(at)5,000 RPM.  Thus a 20A relay would be suitable if each B lead produces 10A max.  Since Rotax calls the voltage regulator a rectifier/regulator I am assuming each B lead is single phase AC but I am not clear as to how breaking one B lead would shut down the alternator. 	
 

   You have two wires coming out of a wall socket to

   power some device, but the ON-OFF switch needs to

   open or close only one leg of the wall-power to

   control the device. Those are not "B" (battery)

   leads coming off the engine. They are as you've

   guessed, two leads with single phase, AC power on them.



   The B-leads are the "R" and "B+" wires that

   come off the rectifier/regulator.



   Breaking one of the green ac power input leads

   is the same as the single switch on your desk

   lamp. The PM alternator continues to develop

   voltage but it has no place to go.



 

  	  Quote: 	
		    A couple of questions:  Why both a fusable link and 5A CB in series on the master sw/OV disconnect relay? 	
 

   This is to accommodate some legacy design rules adopted

   from certified aircraft . . . since the power to operate

   the relay is so small, and since you've elimnated the

   need for a pilot accessible circuit breaker, I'll suggest

   you eliminate both the fusible link and the 5A breaker.

   Power your alternator control circuit directly from a

   3A fuse on your main bus.



  	  Quote: 	
		      How does breaking one line from the 'dynamo' shut it down, or does it?  Per this schematic power is required from the battery to close the OV disconnect relay and bring the 'dynamo' on-line.  Thus with a dead battery there is no way to bring the 'dynamo' on-line? 	
 

   Right. But given what we know about the internals

   of the rectifier regulator, it doesn't matter. It's

   not self-exciting. I suspect we could do a "band-aid"

   not unlike that which was developed for the SD-8 and

   shown in the latest z-figures . . . but the proof-of-

   concept study has not been accomplished for that

   product.  If you have a dead battery, the prudent

   action is to recharge it from some ground based source

   before you start the engine to go flying.



   Except for elimination of the fusible link and CB,

   what you've proposed should work as advertised.



 

 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------



     [quote][b]

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rv8iator

Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR

Posted: Mon Mar 16, 2009 5:05 am Post subject: Rotax w/ Perihelion OVM

Thanks Bob... et al.



This list is a wonderful resource.  Saves me unknown hours researching!



Chris



do not archive



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_________________
C. Stone (RV8iator)

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