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Rotax Voltage Regulator

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Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sat Aug 18, 2007 1:44 pm Post subject: Rotax Voltage Regulator

All,

         It looks like my Rotax 582 three phase voltage regulator's 

dying. (It will occasionally go over voltage. I can re-set it and get 

it to work, but it's happening more often now.)

         Does anyone have a recommended replacement? I've mounted it 

in the engine compartment to minimize electrical noise in the cockpit 

and I suspect things are a little hot for the stock Rotax unit. Has 

anyone tried any of the Harley replacements? Any after-market units? 

Or should I just increase the cooling to the Rotax unit?



Thanks,

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sat Aug 18, 2007 3:53 pm Post subject: Re: Rotax Voltage Regulator

Guy,

Are you sure its not the battery geeting aged. regulators dont usually deteriorate in the way you describe, but a poor internal resistance battery may bring on the symptom.



Ralph

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_________________
Ralph - CH701 / 2200a

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sat Aug 18, 2007 5:35 pm Post subject: Rotax Voltage Regulator

At 04:53 PM 8/18/2007, you wrote:

 	  Quote: 	
		  Are you sure its not the battery geeting aged. regulators dont 

usually deteriorate in the way you describe, but a poor internal 

resistance battery may bring on the symptom.


	


I'm intrigued, since this battery has been nearly dead twice and 

resurrected with a BatteryMinder. I read Bob's section on regulator 

failures and it seems like the over-voltage condition should be 

permanent, and not intermittent. (It seems like it doesn't work when 

cold, then with my switching it in and out it finally starts to 

regulate the voltage. Once it's working it never quits. And if I 

re-start it seems to work fine.) I'll dig into Bob's book to try to 

find an easy way to check internal resistance.



Thanks,

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

nuckollsr(at)cox.net
Guest

Posted: Sat Aug 18, 2007 9:31 pm Post subject: Rotax Voltage Regulator

At 06:26 PM 8/18/2007 -0700, you wrote:

 	  Quote: 	

At 04:53 PM 8/18/2007, you wrote:

>Are you sure its not the battery geeting aged. regulators dont usually 

>deteriorate in the way you describe, but a poor internal resistance 

>battery may bring on the symptom.

I'm intrigued, since this battery has been nearly dead twice and 

resurrected with a BatteryMinder. I read Bob's section on regulator 

failures and it seems like the over-voltage condition should be permanent, 

and not intermittent. (It seems like it doesn't work when cold, then with 

my switching it in and out it finally starts to regulate the voltage. Once 

it's working it never quits. And if I re-start it seems to work fine.) 

I'll dig into Bob's book to try to find an easy way to check internal 

resistance.

Thanks,

Guy Buchanan

   Intermittent voltage excursions both upward and downward

   are manifestations of ageing components and/or internal

   connections that have become less than the best we know

   how to do.

   I believe John Deere (and others) offer a 3-phase

   rectifier/regulator for their 25-40 amp PM alternators.

   I searched the web hoping to find some maintenance

   data or at least some part numbers. No joy.

   Anyone out there have some experience with the larger

   3-phase PM alternator products.

   I've got to visit a customer Monday on the west side

   of town near a John Deere dealership. I'll see if there's

   a helpful individual there who can give me more data

   on the larger PM alternator systems.

   Now, this is an excellent DIY project. We've explored

   the inner workings of the various PM alternator rectifier/

   regulators. I've taken an exemplar single phase R/R

   schematic and added the SCR and diode to accommodate

   a 3 phase alternator. It's posted at:

http://www.aeroelectric.com/Pictures/Schematics/3-Phase_PM_Rectifier_Regulator.gif

   This is a case where the electronics are pretty

   much a no-brainer but the task to be mounted and

   solved is getting the heat out. Average voltage drop

   in one of these regulators is 2.2 volts. So if you're

   dragging 30A from a really husky alternator, the

   R/R needs to get rid of 66W of heat.

   This is where attention is paid to the diodes and

   SCRs to use beefy devices with low thermal resistances

   and then mount them in an enclosure suited for conducting

   that much heat out of the box.  Problems with longevity

   of the PM R/R have roots more in cooling than in the

   absolute ratings of the components.

   For this design, I might even consider putting the

   hot parts on a finned heat sink and blowing air through

   the assembly. There's a wealth of 12V DC brushless

   fans out there to consider. I think I'd also add

   some form of temperature sensing to at least light

   a warning light and allow the pilot to consider a

   temporary load reduction.

   Just some food for thought. As soon as the support

   tools and materials for our hardwood floor project

   are out of the garage, I'll get started on the alternator

   drive stand . . . should be able to run some experimental

   regulator/alternator combinations on the bench this fall.

   Bob . . .

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Hoffmann.RS(at)T-Online.d
Guest

Posted: Sun Aug 19, 2007 12:31 pm Post subject: Rotax Voltage Regulator

Rotax rectifier / regulators (and the other  motorcycle types too) are not unproblematic. As Gilles found out by direct  experiment at nominal power the maximum temperature for the 912 / 914 series R/R  is minus 59° Celsius:<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office" /> 

http://contrails.free.fr/elec_ducati.php   

This is somewhere in the vicinity of the liquid  CO2, please forgive me that I cannot transfer it to Fahrenheit units by heart  (.  

I used a standard 3” vent from a computer power  unit mounted upon the cooling fins to make the system reliable, as Bob mentioned  too. Nevertheless the power output of the 2 phase Rotax alternator is marginal.   

A friend experienced a trip of the main circuit  breaker when operating the flaps at idle. Imagine what would have happened with  an electrical dependent 914 engine. His Dynon and his GPS went black too (which  is not an issue at the home airport). I am aware that he might beef up his 7Ah  battery a little bit, too (  

Increased use of glass panel instruments with  reasonable brightness, strobes etc. would ask for a state-of-the-art generator  system for the future. It is not very elegant to use a reduction gear and then  mount a generator driven by a belt from the prop axis to increase rpms again. It  is more elegant to mount a second generator the crankshaft itself rotating at  some 5000rpm at the back of the 912/914, which has been done:   

http://contrails.free.fr/elec_second_alternateur.php 

If You can live with one sole generator  providing sufficient power, the standard Rotax system should be modified.   

With the existing standard 2phase coil system I  can imagine that a more modern regulator could work not at the frequency  determined by engine rotation, but at a higher frequency as a real switching  regulator with a corresponding higher efficiency; maybe some inductivity would  have to be added. 

I would however prefer another way of solving  the problem. As the rpm is high enough, why not integrate a common 3phase  generator into the original site of the Rotax coils? One wound have to redesign  the (presumably 9) stator coils for the given dimensions and add a rotor with  coil. Add a standard regulator and You are done: greater power mainly because of  better efficiency, no high frequency switching problems, standard technology and  reliability, no belt to break, no hump in streamlined cowlings… Would be just a  standard generator put into the Rotax. 

By the way: You could even get rid of any  sliprings without any electric change at all. Honda has done that on their  CB500f motorcycles even some years ago: 

http://www.autoschrauber.de/content/000058/image/limakomplett.jpg 

The only disadvantage is the introduction of an  air gap. When reliability is an issue, that could be a good trade-off for  aircraft use anyway: almost no moving parts J. 

As Bob already stated, it would be an excellent  DIY – project - not without future potential. 

  

Richard

   [quote][b]

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