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Rotax-B & C over voltage protection

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 09, 2009 6:35 pm Post subject: Rotax-B & C over voltage protection

At 05:38 PM 8/9/2009, you wrote:

 	  Quote: 	
		  



I’m building a Rotax 912uls powered Kolb. The 

used engine I purchased has the stock Rotax 

charging system as well as a B & C SD-20/ LR3C 

backup system. I would like to insure I have 

proper over voltage protection on both systems. 

I see the LR3C claims to have over voltage 

‘crowbar’ protection but I see no listing of 

what voltage it considers too high. Anyone know 

where to find that info? Also, as I understand 

it there is no form of over voltage protection 

on the Rotax system. I assume this is where 

Bob’s OVM-14 comes in and I’ll be happy to 

add one. What voltage does the OVM-14 consider too high? Thanks,


	


   Industry "rule of thumb" for OV protection in 14v systems

   is 16.2 to 16.5 volts. This is the voltage setpoint I

   designed into all of B&C's ov protection systems whether

   built in or external. It's also the trip voltage setpoint

   range for our OV protection products.

        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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icrashrc

Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In

Posted: Mon Aug 10, 2009 11:35 pm Post subject: Re: Rotax-B & C over voltage protection

Bob,



Thanks, I'll get one of your over voltage modules on order. Any idea if the Rotax charging system output voltage is adjustable?



Scott

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Aug 11, 2009 7:21 am Post subject: Rotax-B & C over voltage protection

At 02:35 AM 8/11/2009, you wrote:

 	  Quote: 	
		  



Bob,



Thanks, I'll get one of your over voltage modules on order. Any idea 

if the Rotax charging system output voltage is adjustable?


	


   I don't believe it is. I'd like to find the time

   someday to craft a really modern rectifier/regulator

   that contains built in OV protection and adjustable

   regulation set point. I've got too many irons in

   the fire . . .

        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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rparigor(at)SUFFOLK.LIB.N
Guest

Posted: Tue Aug 11, 2009 8:44 pm Post subject: Rotax-B & C over voltage protection

Hi Bobs"Any idea f the Rotax charging system output voltage is adjustable?'"I don't believe it is."I  mentioned this in the past (Bob I think you said it has a good chance of doing as advertised), I read a post in the Europa newsgroup how one can increase setpoint on Ducati regulator (others as well). I plan to do this as Ducati factory setpoint is lower than I would like for PC545 Odyssey.Below is the post from Europa newsgroup, havn't tried it yet though.Ron Parigoris[quote]  	  Quote: 	
		  "I also have that Ducati-thing on the other

alternator. Guess I have to

  	  Quote: 	
		  put a diode in series with its sense lead to

crank up the voltage

somewhat."

	
 Good idea to increase setpoint if you can. Where

exactly would you put

diode in circuit? What value diode?

	
 Most regulators have multiple 12 Volt connection

points. So does the

Ducati regulator. One of these 12 Volt points (the one labeled 'C') has

the sole purpose of measuring the voltage. You can connect this directly

to the adjacent connector (B, or R, which carries the actual output) as

is often done, so it measures its own output, but a more correct way is

to connect it directly to the battery, so that any voltage drop over the

feeder cable is corrected. Suppose you want to have a voltage over the

battery of 13.7 Volts, and the cables have a loss of 0.5 Volt, then

connected in this way the regulator will crank up the voltage until it

sees 13.7 Volts at the battery, i.e. it will output 14.2 Volts to

correct the voltage drop over the main cable. Ok, I guess almost nobody

does this as most people don't know about it. BTW, The regulator for the

SD20S alternator has a similar option.

You can however do more with this if you are creative. A standard diode,

like a 1N400x, has a forward voltage drop of about 0.6 / 0.7 Volts. So,

if you put this diode in series with the wire connected to the C, the

regulator will see 0.7 Volts less than the actual voltage. It will

therefor output more to correct for this condition. With other words,

the output will increase with 0.7 Volts.

The diode will not carry any significant current, any rating will

suffice. You could put multiple diodes in series if you want to have a

multiple of 0.7 Volts. A Skottky diode has a forward drop of about 0.2

Volts. You can also use a resistor divider to increase the output with

any value, but keep in mind that a resistor also divides the voltage

fluctuations while a diode is absolute, so using a resistor divider is

somewhat less stable. Another trick is to use a temperature sensitive

resistor, so the regulator will adjust the voltage according to the

temperature, something that is highly appreciated by the battery.

--

Frans Veldman

[b]

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icrashrc

Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In

Posted: Wed Aug 12, 2009 2:07 am Post subject: Re: Rotax-B & C over voltage protection

If you build it they will come.



 	  nuckolls.bob(at)aeroelect wrote: 	
		  At 02:35 AM 8/11/2009, you wrote:

 	  Quote: 	
		  



Bob,



Thanks, I'll get one of your over voltage modules on order. Any idea 

if the Rotax charging system output voltage is adjustable?



	


   I don't believe it is. I'd like to find the time

   someday to craft a really modern rectifier/regulator

   that contains built in OV protection and adjustable

   regulation set point. I've got too many irons in

   the fire . . .

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
Scott

www.ill-EagleAviation.com

do not archive

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 12, 2009 12:57 pm Post subject: Rotax-B & C over voltage protection

At 11:41 PM 8/11/2009, you wrote:

  	  Quote: 	
		  Hi Bobs



 "Any idea f the Rotax charging system output voltage is adjustable?'



 "I don't believe it is."



 I  mentioned this in the past (Bob I think you said it has a good chance of doing as advertised), I read a post in the Europa newsgroup how one can increase setpoint on Ducati regulator (others as well). I plan to do this as Ducati factory setpoint is lower than I would like for PC545 Odyssey.



 Below is the post from Europa newsgroup, havn't tried it yet though. 	  Quote: 	
		    A standard diode,

  like a 1N400x, has a forward voltage drop of about 0.6 / 0.7

Volts. So,

  if you put this diode in series with the wire connected to the C,

the

  regulator will see 0.7 Volts less than the actual voltage. It

will

  therefor output more to correct for this condition. With other

words,

  the output will increase with 0.7 Volts.

	
	




    That's a pretty standard work-around for boosting

    the setpoint on an unadjustable regulator. This must

    be applied with caution on some regulators. For example,

    if the diode were used to jack up the voltage on an

    regulator wound-field alternator, where field supply

    and voltage sense wires share the path. Adding external

    components in shared lines can contribute to or cause

    regulation instability.



    When it is known that the sense line current is low

    (100 ma or less) then adding diodes or even series

    resistors to adjust the setpoint upward is often quite

    successful.



 

 

        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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icrashrc

Joined: 16 Mar 2006
Posts: 247
Location: Mishawaka, In

Posted: Thu Jul 01, 2010 12:02 pm Post subject: Re: Rotax-B & C over voltage protection

Bob,



I finally got around to taking the OVM-14 you sent out of the package. I just want to double check that this is a hearty enough unit to drop the 30 amp breaker called for in the Rotax 912 schematics. There doesn't seem to be a separate field breaker called for. Do i maybe have to install it elsewhere? Thanks,



Scott

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 01, 2010 8:03 pm Post subject: Rotax-B & C over voltage protection

At 03:02 PM 7/1/2010, you wrote:

 	  Quote: 	
		  



Bob,



I finally got around to taking the OVM-14 you sent out of the 

package. I just want to double check that this is a hearty enough 

unit to drop the 30 amp breaker called for in the Rotax 912 

schematics. There doesn't seem to be a separate field breaker called 

for. Do i maybe have to install it elsewhere? Thanks,


	


    In no set of instructions is the OVM expected to open

    any breaker over 5A.

    Since the 912 schematics don't address ov protection

    of any type, you're stuck with installing as shown

    in . . .



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

   Bob . . .

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