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Schematic for twin PM alternators
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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jan 19, 2016 5:27 am Post subject: Schematic for twin PM alternators

At 10:04 PM 1/18/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net



 Hi Joe;

 Being internally regulated, each alternator has it's own regulator.  I think I will probably wire so that only one is in use at a time.

 Cheers! 	


    Oops! So the design goals do not include

    simultaneous exploitation of both alternators?

    How do you plan to use this airplane and

    how would the twin alternator installation

    fit into your failure analysis?



 

 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jan 19, 2016 8:05 am Post subject: Schematic for twin PM alternators

At 07:25 AM 1/19/2016, you wrote:

  	  Quote: 	
		  At 10:04 PM 1/18/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net



 Hi Joe;

 Being internally regulated, each alternator has it's own regulator.  I think I will probably wire so that only one is in use at a time.

 Cheers! 	


    Oops! So the design goals do not include

    simultaneous exploitation of both alternators?

    How do you plan to use this airplane and

    how would the twin alternator installation

    fit into your failure analysis? 	




 To: ashleysc(at)broadstripe.net

 Subject: Re: Re: Schematic for twin PM alternators



 At 09:42 PM 1/18/2016, you wrote:

  	  Quote: 	
		  Hi Bob;

 1.  OK.  Amounts to the same thing.

 2.  Actually I removed the axially driven externally regulated permanent magnet alternator provided by the engine builder to allow reinstalling a harmonic balancer, which he did not feel was necessary.  The two belt driven 12V, 20 amp permanent magnet internally regulated alternators are being provided by me.  Seems odd that no one has done this, but as a retired electro-mechanical engineer, I will work something out when the time comes. 	




    Twin belt driven alternators on an engine

    is an exceedingly rare configuration . . . in

    fact . . . I'm not aware of anyone having

    opted for this arrangement. Doesn't mean it

    hasn't happened . . .



    If your goal is to achieve 40A of engine

    driven capacity, why two separate 20A machines

    with no known capability for sharing loads

    when driving a common bus? Why not a little

    40A ND alternator with a track record?



    I've been pondering the twin-stators on the

    VW variant. It just may be that the two windings

    ARE driven by the same set of magnets, are

    the same number of turns and enjoy the same

    magnetic efficiency for gathering forces from

    the moving magnets for conversion to electron

    flow.



    If that IS the case, I would think that the

    Revmaster installation would recommend parallel

    connection of the two windings along with a

    suggested rectifier-regulator good for 40A.



    Herein lies the uncertainties. THAT much output

    from a single phase R-R is hard, every machine of

    that power output I'm  aware of is a

    three phase output with the best R-R designs

    going to synchronous field effect rectification

    to reduce losses.  A legacy R-R design is a rather

    inefficient device that begs good thermal management

    of dissipated energy. The larger the output,

    the more energy dissipated . . . and NOT available

    to run your electro-whizzies.



    We know that the track record for Ducatti R-R

    supplied with Rotax 912/914 engines has a spotty

    track-record . . . and that's only an 18A rated

    alternator.



    There are many, much more robust products

    for upgrading the 18A Rotax system. Those

    same regulators might be considered for the

    dual-coil Revmaster system.



    I don't have any way to drive two PM alternators

    simultaneously to explore the effectiveness of

    PARALLELING two alternator-rectifier-regulators

    to the same bus. I'm not saying it WILL NOT work

    very nicely . . . I'm just saying I have no practical

    way to say, "been there, done than, works good,

    lasts a long time".



    So you are the pioneering integrator here. When

    you run the engine the first time, it would be

    useful/interesting to instrument your new,

    twin alternator configuration, apply various loads

    to the system and see how well they share duties

    for grunting a 40A load.



    If they parallel to within 10-20% of each other,

    odds are that your chosen configuration will

    meet your design goals for a 40A, PM system.



    The ball is in your court . . .



 

 

   Bob . . .

N509RV(at)eckenroth.com
Guest

Posted: Tue Jan 19, 2016 12:24 pm Post subject: Schematic for twin PM alternators

I did what I probably should have done at the beginning and made a list of amperage draw items.  The total will allow for the use of one alternator with the other kept in reserve.  So Joe's schematic will work for me.  Now I have to become comfortable with the ramifications.



When the reserve generator is not working due to no power at the IGW terminal what is happening.  Is everything dormant associated with that generator or is the generator still cranking away creating heat in the regulator.How about when the crowbar trips.  The IGW is still energized.  What happens to the regulator/generator.

There are two switches that determine which generator is functional.  Can those be combined.



Thanks for all the help

Paul

On Tue, Jan 19, 2016 at 11:02 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 07:25 AM 1/19/2016, you wrote:

  	  Quote: 	
		  At 10:04 PM 1/18/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)



 Hi Joe;

 Being internally regulated, each alternator has it's own regulator.  I think I will probably wire so that only one is in use at a time.

 Cheers! 	


    Oops! So the design goals do not include

    simultaneous exploitation of both alternators?

    How do you plan to use this airplane and

    how would the twin alternator installation

    fit into your failure analysis? 	




 To: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)

 Subject: Re: Re: Schematic for twin PM alternators



 At 09:42 PM 1/18/2016, you wrote:

  	  Quote: 	
		  Hi Bob;

 1.  OK.  Amounts to the same thing.

 2.  Actually I removed the axially driven externally regulated permanent magnet alternator provided by the engine builder to allow reinstalling a harmonic balancer, which he did not feel was necessary.  The two belt driven 12V, 20 amp permanent magnet internally regulated alternators are being provided by me.  Seems odd that no one has done this, but as a retired electro-mechanical engineer, I will work something out when the time comes. 	




    Twin belt driven alternators on an engine

    is an exceedingly rare configuration . . . in

    fact . . . I'm not aware of anyone having

    opted for this arrangement. Doesn't mean it

    hasn't happened . . .



    If your goal is to achieve 40A of engine

    driven capacity, why two separate 20A machines

    with no known capability for sharing loads

    when driving a common bus? Why not a little

    40A ND alternator with a track record?



    I've been pondering the twin-stators on the

    VW variant. It just may be that the two windings

    ARE driven by the same set of magnets, are

    the same number of turns and enjoy the same

    magnetic efficiency for gathering forces from

    the moving magnets for conversion to electron

    flow.



    If that IS the case, I would think that the

    Revmaster installation would recommend parallel

    connection of the two windings along with a

    suggested rectifier-regulator good for 40A.



    Herein lies the uncertainties. THAT much output

    from a single phase R-R is hard, every machine of

    that power output I'm  aware of is a

    three phase output with the best R-R designs

    going to synchronous field effect rectification

    to reduce losses.  A legacy R-R design is a rather

    inefficient device that begs good thermal management

    of dissipated energy. The larger the output,

    the more energy dissipated . . . and NOT available

    to run your electro-whizzies.



    We know that the track record for Ducatti R-R

    supplied with Rotax 912/914 engines has a spotty

    track-record . . . and that's only an 18A rated

    alternator.



    There are many, much more robust products

    for upgrading the 18A Rotax system. Those

    same regulators might be considered for the

    dual-coil Revmaster system.



    I don't have any way to drive two PM alternators

    simultaneously to explore the effectiveness of

    PARALLELING two alternator-rectifier-regulators

    to the same bus. I'm not saying it WILL NOT work

    very nicely . . . I'm just saying I have no practical

    way to say, "been there, done than, works good,

    lasts a long time".



    So you are the pioneering integrator here. When

    you run the engine the first time, it would be

    useful/interesting to instrument your new,

    twin alternator configuration, apply various loads

    to the system and see how well they share duties

    for grunting a 40A load.



    If they parallel to within 10-20% of each other,

    odds are that your chosen configuration will

    meet your design goals for a 40A, PM system.



    The ball is in your court . . .



 

 

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Jan 19, 2016 5:04 pm Post subject: Re: Schematic for twin PM alternators

Paul,

I posted two schematics.  Which one are you referring to, the first or second?

Here is a link to the second one:

http://forums.matronics.com/download.php?id=42255

My comments below will reference the second one.

The 3 Pole, Single Throw, (3PST) switch is the master switch.  It controls the battery master contactor and also both rectifiers/regulators Ignition terminals.  When the master switch is turned on, the battery contactor is energized and both regulators are turned on.  In case of smoke in the cockpit, I think that it is a good idea for the master switch to be able to shut off all electrical power from not only the battery but also from the alternators.  The separate alternator switch selects which one of the two alternators to use, or both off.  I suppose that all switch functions could be combined into one switch at the risk of putting all eggs into one basket.  It is questionable if that one switch would reduce pilot workload or make the system any more intuitive.

If there is no power going to a regulator Ignition terminal, then that regulator is shut off.  Its dynamo is still generating AC voltage whenever the engine is running, but no current flows when the regulator disabled and very little heat is made.  Heat goes up with the load on the aircraft electrical system.

 If the over-voltage breaker trips or if the selector switch is shut off, then the alternator relay is de-energized and the alternator power output is shut off.  

That situation is no different than if the pilot shuts off each individual electrical load one device at a time.  The dynamo-regulator can not tell the difference between all individual switches being shut off or one relay shutting everything off.

 The MIA881279 rectifier/regulator is the replacement part number for the John Deere AM101406 that some have used to replace the Rotax R/R.

 Unlike Bob's architecture, my schematic is unproven.  So I welcome any comments or suggestions to prevent steering Paul in the wrong direction.

_________________
Joe Gores

ashleysc(at)broadstripe.n
Guest

Posted: Tue Jan 19, 2016 6:53 pm Post subject: Schematic for twin PM alternators

Hi Bob;



 I would parallel them if there is no hazard.  Otherwise I will run them separately.  This is a daytime, VFR aircraft, that I hope to take some long cross countries in.  It would have two alternators and one battery.  The idea would be not to have to truncate a trip due to one failure.

 Cheers!   Stu.

 



   From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

To: aeroelectric-list(at)matronics.com

Sent: Tuesday, January 19, 2016 5:25:04 AM

Subject: Re: Re: Schematic for twin PM alternators

 



At 10:04 PM 1/18/2016, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: ashleysc(at)broadstripe.net

 



Hi Joe;

Being internally regulated, each alternator has it's own regulator.  I think I will probably wire so that only one is in use at a time.

Cheers! 	


   Oops! So the design goals do not include

   simultaneous exploitation of both alternators?

   How do you plan to use this airplane and

   how would the twin alternator installation

   fit into your failure analysis?

 

 

  Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Wed Jan 20, 2016 1:10 pm Post subject: Re: Schematic for twin PM alternators

I revised my schematic and attached it.

The relays now switch the AC.  All electrical power can be shut off on the engine side of the firewall.

The DC output from each regulator is fused separately so that a fault in one will not disable the other one.

Revmaster5a.pdf

Description:

Download

Filename:

Revmaster5a.pdf

Filesize:

68.22 KB

Downloaded:

363 Time(s)

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Wed Jan 20, 2016 1:49 pm Post subject: Schematic for twin PM alternators

On Wed, Jan 20, 2016 at 3:10 PM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 I revised my schematic and attached it.

 The relays now switch the AC.  All electrical power can be shut off on the engine side of the firewall.

 The DC output from each regulator is fused separately so that a fault in one will not disable the other one.

 

 --------

 Joe Gores

 

	




I wish I had the time/aptitude to knock out nice drawings like that. I'm still scribbling in notebooks.



Some thoughts.

The path from buss through the  alt breaker, SPDT switch contains multiple single points of failure that can take out both alternators.

The alternators, as drawn in the original 'cartoon' installation drawing seems to show one leg of each alternator connected to ground. If that's the case, interrupting the 'wrong' leg might not shut that alt down, if there's an internal short to ground.

Behavior of the IGN terminal is not known, and even if it does control the alt, there's no guarantee that a failure mode won't keep the alt active.

Assuming that the IGN terminal can control the alt, the ganged master is a single point of failure for the alts (though if it goes, the alts may not matter.  ).

With B leads tied to the buss, a failure to ground in either charging system might try to draw power from the buss (battery & other alt).

Some of the above may not be important if it's a purely VFR plane with no electrical dependence, & nav can be handled with eyeballs &/or portable nav/gps units. But it shouldn't be too difficult to make the system truly redundant. (Independent OV modules, separate switches, contactors interrupting the B leads, etc)

What do you think?

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Wed Jan 20, 2016 5:21 pm Post subject: Re: Schematic for twin PM alternators

 	  Quote: 	
		  I wish I had the time/aptitude to knock out nice drawings like that. 	


It helps to be retired.

You are right about the multiple single points of failure in the relay coil circuit.  To eliminate the danger, the circuit would have to be duplicated; 2 breakers, 2 capacitors, and two switches.  The builder would have to weigh the danger of a single part failing against the disadvantage of adding more parts.

I did not see any documents that indicated the AC winding was grounded.  That would be easy to check with an ohmmeter.

I assume [I know that is dangerous  ] that the MIA881279 regulator terminals have the same functions as the Rotax regulator.  See this thread:

http://www.matronics.com/forums/viewtopic.php?p=305164&sid=53455a09f9026927ea6c15eb6d6e198f

 	  Quote: 	
		  there's no guarantee that a failure mode won't keep the alt active. 	


A regulator can not have an output if there is no AC input.  The relays only allow one AC dynamo to be connected at a time.

 	  Quote: 	
		  the ganged master is a single point of failure for the alts 	


Yes, but many airplanes have a master switch that is a single point of failure.

 	  Quote: 	
		  With B leads tied to the buss, a failure to ground in either charging system might try to draw power from the buss (battery & other alt). 	


True, but it would have to be a resistive fault.  A direct short to ground would blow the 25 amp fuse with battery current.

Yes, the circuit could be made more failure tolerant.  But is added complexity warranted for the aircraft mission?  This is a hobby for me.  I do not want to make it into a full time job.  

You bring up some interesting points.  If it were my plane intended for hard IFR, then I would spend more time honing the schematic.

_________________
Joe Gores

N509RV(at)eckenroth.com
Guest

Posted: Thu Jan 21, 2016 8:29 am Post subject: Schematic for twin PM alternators

I like the revised schematic in that it is breaking the AC feed from the dynamo and therefore eliminating any concern about what the regulator will do with the AC current when it is not engaged.  However, a failure in the charging circuit that causes the crowbar to trip the AC current will probably be in the regulator.  You will still have battery voltage back feeding the regulator through the B tab.  Can that create any problems.Is there a reason that the capacitor is in the position shown.  I would have thought it should be attached to the B output since it's purpose is to smooth out the voltage output.  

The Onex is a small aerobatic plane that will be flown VFR daytime only.  However it will be equipped so it can be flown at night and escape from any inadvertent VFR into IIFR situations. As such and with the backup generator and independent ignitiion I don't feel that a E bus is needed.

I welcome all input.

Paul 

On Wed, Jan 20, 2016 at 4:10 PM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

 

 I revised my schematic and attached it.

 The relays now switch the AC.  All electrical power can be shut off on the engine side of the firewall.

 The DC output from each regulator is fused separately so that a fault in one will not disable the other one.

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=452147#452147

 

 

 

 

 Attachments:

 

 http://forums.matronics.com//files/revmaster5a_214.pdf

 

 

 

 

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Thu Jan 21, 2016 3:24 pm Post subject: Re: Schematic for twin PM alternators

 	  Quote: 	
		  will still have battery voltage back feeding the 

regulator through the B tab 	


When I turn on the master switch on my RV-12 and before 

starting the Rotax, battery voltage is being back fed to the 

regulator B terminal.  Of course the regulator is in working 

condition.  Who knows what regulator failure modes there are 

besides low voltage.

 I do not think that it matters much where the capacitor is 

connected to the positive supply as long as it is connected 

whenever the alternator is working.  I think it is a good idea 

to use a fuse or circuit breaker to protect the electrical 

system against the capacitor shorting.

The E-Bus is the main feature of Bob's designs that improves 

upon legacy aircraft electrical systems.  It provides an 

alternate current path if the main path fails.  I recommend it.

 I have attached another schematic that incorporates some ideas 

suggested by others.  I am not necessarily recommending it.  

The design has an additional circuit breaker and an additional 

capacitor.  It is more complicated to wire, but from a pilot's 

perspective, there is still one alternator switch and one 

master switch.  If there is a concern about the master switch failing,

then install 2 of them next to each other wired in parallel.

Revmaster6a.pdf

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Filename:

Revmaster6a.pdf

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_________________
Joe Gores

Paul Eckenroth

Joined: 29 Jun 2010
Posts: 14

Posted: Tue Jan 26, 2016 7:42 am Post subject: Re: Schematic for twin PM alternators

Joe Gores was kind enough to produce a schematic (enclosed) that pretty much answers all my concerns about the twin alternators.  Since my amperage needs are less than 20 AMPs we will keep the two generators separate and treat them as primary and backup.  The crowbar will break both the AC from the generator and the B lead from the voltage regulator eliminating any problems from the regulator.

And then I read the post by GTH and the report he did for Contrails magazine regarding testing of the Rotax supplied regulator where they found that the regulator generated heat was proportional to the generated power.  With this in mind and with the fairly high rate of failure of the Rotax regulator presumably due to heat, would it be likely that tying the two Revmaster generator outputs together after the regulators would result in less power produced by each and therefore longer life for the regulators.  Possibly this could be done so there is flexibility to run individually as now planned or together.  Would there be a way to monitor the output of the individual generators if tied together at the battery, to see how equal they are.



So I would appreciate any comments and critiques regarding the schematic as it now stands and the alternate thought of combining them for less trauma to the regulators.



Thanks for any feedback

Paul

Revmaster7a (1).pdf

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