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Load Monitoring

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al38kit

Joined: 13 Jul 2009
Posts: 21

Posted: Sat Aug 01, 2009 3:28 pm Post subject: Load Monitoring

I'm considering using two alternators, the 20 Amp B&C, and the 60 AMP Plane Power.  I'm also considering using two PP regulators, as it appears that they will load share as a percent of output...I'm going to use a JPI 930 that has the ability to monitor two locations with 50mv shunts...they sell 100 AMP units at $75 a pop...I thought that to be a little much for a shunt...



I think I read that you were using 50mv shunts in your load meter set up and that they were matched or calibrated or something...



Do you think that using two of them on the load meter of the JPI would be a good idea...and how much are they?



Any other comments welcome, especially on the PP regulators and the load sharing feature.



PS...I found the Tyco EV200 relays for $50, delivered...so I bought them.



Thanks,



Al Kittleson

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Aug 01, 2009 5:06 pm Post subject: Load Monitoring

At 06:28 PM 8/1/2009, you wrote:

 	  Quote: 	
		  



I'm considering using two alternators, the 20 Amp B&C, and the 60 

AMP Plane Power.  I'm also considering using two PP regulators, as 

it appears that they will load share as a percent of output...I'm 

going to use a JPI 930 that has the ability to monitor two locations 

with 50mv shunts...they sell 100 AMP units at $75 a pop...I thought 

that to be a little much for a shunt...



I think I read that you were using 50mv shunts in your load meter 

set up and that they were matched or calibrated or something...



Do you think that using two of them on the load meter of the JPI 

would be a good idea...and how much are they?



Any other comments welcome, especially on the PP regulators and the 

load sharing feature.



PS...I found the Tyco EV200 relays for $50, delivered...so I bought them.



Thanks,



Al Kittleson


	


   Please don't do this. The elegant application of

   the two alternators is EITHER as shown in

   Z-11 or INDEPENDENT W/cross-feed as shown in

   Z-14.



   What are your load requirements that you think you'll

   ever need the combined output of both alternators to

   drive a single bus?

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

al38kit

Joined: 13 Jul 2009
Posts: 21

Posted: Sat Aug 01, 2009 6:03 pm Post subject: Re: Load Monitoring

Sorry to not word the question better regarding the shunts.



I was generally thinking of a design along the lines of Z-14...my thought was to run with the crossfeed tie closed in normal operation and use both alternators to feed the tied busses...



If that is a bad idea, then I'll run split busses.



My monitor should function the same way, regardless of whether the buss tie is open or closed...that is where the question regarding the shunts enters the picture. 



Thanks,



Al

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 02, 2009 6:22 am Post subject: Load Monitoring

At 09:03 PM 8/1/2009, you wrote:

 	  Quote: 	
		  



Sorry to not word the question better regarding the shunts.



I was generally thinking of a design along the lines of Z-14...my 

thought was to run with the crossfeed tie closed in normal operation 

and use both alternators to feed the tied busses...



If that is a bad idea, then I'll run split busses.


	


   The cross-tie is used only when one alternator has

   failed and there's a useful mode of operation where

   one alternator can feed equipment on both sides.

   The cross-tie contactor is closed only for engine

   cranking and single-alternator operations.



 	  Quote: 	
		  My monitor should function the same way, regardless of whether the 

buss tie is open or closed...that is where the question regarding 

the shunts enters the picture.


	


   If you've done your homework (load analysis) then

   the amount of power required of either alternator is

   known before-hand for all flight conditions. In

   other words, your plan-A, plan-B . . . plan-x execution

   should not depend on reading an ammeter. But if your

   electrical system monitoring device(s) come with

   hall effect sensors, then they can go on the alternator

   b-leads. For the most part, current displays are most

   useful on the ground as trouble shooting assists.



   Run each alternator with its own, stand alone regulator

   and ov protection . . . and if your glass panels do not

   include active notification of low voltage, then that

   feature should be part of your instrumentation planing

   for both sides.



   What airplane are you building where you think you

   can get a good return on investment for Z-14?

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

al38kit

Joined: 13 Jul 2009
Posts: 21

Posted: Sun Aug 02, 2009 7:35 am Post subject: Re: Load Monitoring

Bob,



I think we have a numbers of things that have come up regarding my original question...which was inquiring about the 50mv shunts and their price, which was the question du jour.



But to answer your question, I'm working on a rebuild of an Express (four place, low wing composite...family mobile, X-C plane)...It has an IO-520, three blade prop.  I already have the 60-70 amp alternator belt driven alternator and the B&C gear driven unit.  



As I don't plan to put in a vacuum system, the Z-14 design appears to be a good choice.



Is there something about the Plane Power regulator that you don't like?



I'm open to ideas, but using a regulator that was designed to load share seems like a good idea, but if it isn't, it's easy to go with the open tie buss design.



I've flown a lot of big airplanes where tying the busses together is ops normal.  I've had some thought of trying this too.  If it is, or turns out to be a bad idea, all I need to do is open the tie buss relay.



I'll do all the normal buss load analysis and thought that an easy way to monitor loads would be to use your shunt, along with the JPI monitor.  This monitor has user settable alarms for current and voltage.   



What are your thoughts on the shunts in this application?  I don't have any hall effect ammeters right now and as the JPI has two shunt type ammeters available, I thought it would be a good idea to use them...



What about the Plane Power regulators?  From talking to the owner of the company, they work in tandem by turning each alternator "ON" for the same period of time.  He claims that dissimilar sized alternators can easily be used in this type of setup.  It's normally used in twin engine aircraft, with one buss.



I'm not attempting to be a heretic, just exploring other options...I have almost all the parts that I have scrounged second hand (Including the JPI monitor)...



How about "them shunts"...?



Cheers,



Al

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 02, 2009 8:44 am Post subject: Load Monitoring

At 10:35 AM 8/2/2009, you wrote:

 	  Quote: 	
		  



Bob,



I think we have a numbers of things that have come up regarding my 

original question...which was inquiring about the 50mv shunts and 

their price, which was the question du jour.


	


   oops . . . yeah. If your system uses 50mv shunts both

   I and B&C have them in stock in various sizes. I can

   cut larger shunts down to smaller applications as

   well. I think we both get $25.00/ea for them.

 	  Quote: 	
		  But to answer your question, I'm working on a rebuild of an Express 

(four place, low wing composite...family mobile, X-C plane)...It has 

an IO-520, three blade prop.  I already have the 60-70 amp 

alternator belt driven alternator and the B&C gear driven unit.


	


   Oh yeah, I recall that now.

 	  Quote: 	
		  As I don't plan to put in a vacuum system, the Z-14 design appears 

to be a good choice.


	


   Agreed

 	  Quote: 	
		  Is there something about the Plane Power regulator that you don't like?


	


   Not a thing. I'm sure their product performs as advertised. But

   it's not clear that they are true load sharing devices driven

   by DIRECT MEASUREMENT of output from all power generating

   devices. For example, the Hawkers have two engine driven

   generators and one APU driven generator. ALL three can be

   tied to the one bus at the same time. Each generator will

   be loaded to it's proportionate share of the load based on

   individual capability (the APU generator is smaller than

   the other two). This isn't rocket science but it's not

   trivial either.



 	  Quote: 	
		  I'm open to ideas, but using a regulator that was designed to load 

share seems like a good idea, but if it isn't, it's easy to go with 

the open tie buss design.


	


   That's the original design goal for Z-14 for a variety

   of reasons . . . not the least of which is the hassle/

   expense of true load-sharing regulators. I've designed

   and proposed two different load sharing regulators over

   the years. All worked as advertised but were markedly

   more expensive than the stand-alone, single alternator

   regulators. We never went to production with them in

   spite of the fact that the Cessna and Beech light

   twins really needed them. Today, I could do a uP based

   regulator for a small fraction of the cost and much

   better performance . . . neat stuff that software!



   The really cool thing about the old carbon pile

   regulator for generators is their ease of paralleling

   using the relatively high voltage drop in generator's

   compensation windings as a crude shunt. See:



http://aeroelectric.com/Pictures/Schematics/Parallel_Aircraft_Generators.jpg



   a simple addition of a few turns of wire in the

   regulator wired to cross-tied compensation windings

   did a pretty good job of paralleling the generators

   with a minimum parts count. Alternators are a whole

   other problem . . .

 	  Quote: 	
		  I've flown a lot of big airplanes where tying the busses together is 

ops normal.  I've had some thought of trying this too.  If it is, or 

turns out to be a bad idea, all I need to do is open the tie buss relay.


	


   Yup, wiring the 2-50 switch as illustrated gives you

   auto-tie for cranking and leaves the bus-tie contactor

   open unless selected by moving to the opposite position.

 	  Quote: 	
		  I'll do all the normal buss load analysis and thought that an easy 

way to monitor loads would be to use your shunt, along with the JPI 

monitor.  This monitor has user settable alarms for current and voltage.


	




   Very well. We can get the proper shunts into your

   possession through several venues.

 	  Quote: 	
		  What are your thoughts on the shunts in this application?  I don't 

have any hall effect ammeters right now and as the JPI has two shunt 

type ammeters available, I thought it would be a good idea to use them...


	


   If they're already in place, then putting them

   to useful service is not a bad idea. The shunts

   don't weigh much either.

 	  Quote: 	
		  What about the Plane Power regulators?  From talking to the owner of 

the company, they work in tandem by turning each alternator "ON" for 

the same period of time.  He claims that dissimilar sized 

alternators can easily be used in this type of setup.  It's normally 

used in twin engine aircraft, with one buss.


	


   In that situation you MUST do something to

   distribute the loads. Making two IDENTICAL

   alternators, turning THE SAME SPEED approximately

   share loads by what I BELIEVE Plane Power does is

   indeed practical. But I that control philosophy

   wouldn't work with a 60/20 or 40/20 combination

   like Z-14 where the alternators are different from

   each other and turn different speeds.

 	  Quote: 	
		  I'm not attempting to be a heretic, just exploring other options...I 

have almost all the parts that I have scrounged second hand 

(Including the JPI monitor)...


	


   Understand and no fault perceived. Sounds

   like you've got a workable plan that needs

   at most a bit of tweaking.

 	  Quote: 	
		  How about "them shunts"...?


	


   Can fix you up. You can place an order by ordering

   a dual ammeter kit from the website and enter quantity

   of "0" but put values in for the shunts you need.

   Bob . . .

klehman(at)albedo.net
Guest

Posted: Sun Aug 02, 2009 9:05 am Post subject: Load Monitoring

With Z-14 normally running with isolated alternators, I have instant 

notification of either alternator failing due low voltage. With 

paralleled alternators I presume you would add something like low 

current warnings (independent of the regulator) to warn of a bad alternator.

Ken



 	  Quote: 	
		  > Is there something about the Plane Power regulator that you don't like?

 

   Not a thing. I'm sure their product performs as advertised. But

   it's not clear that they are true load sharing devices driven

   by DIRECT MEASUREMENT of output from all power generating

   devices. For example, the Hawkers have two engine driven

   generators and one APU driven generator. ALL three can be

   tied to the one bus at the same time. Each generator will

   be loaded to it's proportionate share of the load based on

   individual capability (the APU generator is smaller than

   the other two). This isn't rocket science but it's not

   trivial either.

 

> I'm open to ideas, but using a regulator that was designed to load 

> share seems like a good idea, but if it isn't, it's easy to go with 

> the open tie buss design.

al38kit

Joined: 13 Jul 2009
Posts: 21

Posted: Sun Aug 02, 2009 9:52 am Post subject: Re: Load Monitoring

Bob,



I really appreciate your insight into this stuff.  I'm not just "kicking the tires" but really plan some installation in the near future and I'm just getting stuff lined up...



Regarding the PP regulators, I'm sure Les said that alternators of dissimilar outputs would load share based upon their respective max values...If, for example, you used the 20/60 amp combo and required 40 amps, each alternator would be tasked with 50% of the load...but I'll check into it...I believe he said that it could be done by each regulator being fired up for the same amount of time...does that make sense to you?



I'm not sure why that would work, but I'm pretty sure that's what he said was the basis for the idea.  I believe both regulators are connected by a single wire that gives the feedback of them "knowing" how long to stay on.



Probably my final question on this topic:  If more current is needed from an alternator than it is able to make, what happens?



I expect that most of these alternators will produce more than the rated current.  At PP they told me that the 60 amp will easily put out more than 70.  I'm not advocating that anyone try it, and I expect there are a lot of bad things that would happen if one tried to do it for a long time.  Excess heat and premature failure are two things I can think of, or even catastrophic failure of the unit...what I'm wondering is...what would occur  if, say, the 60 amp unit failed and only the 20 amp unit stayed on line when the overall requirement was 50 amps.



Would the 20 amp unit continue to do it's job to the best of it's ability, with the battery(s) picking up the slack for as long as they could, or would something worse happen?



I'm wondering as this could be the situation IF the 60 amp unit failed and one continued with the 20.  I expect I could get by indefinitely on the 20 as long it's pitot heat and/or lights were needed...just wondering if when that occurred, what would happen.



I suspect that the alternator would do what it could and that the battery(s) would pick up the slack with the buss voltage going down from 13.8-14 to whatever voltage the batteries could supplement...like 12.2  something...



What do you think?



Sorry if this is an old question, but I'm new to the forum and didn't find anything with a search.



Thanks again,



Al

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 02, 2009 11:17 am Post subject: Load Monitoring

At 12:04 PM 8/2/2009, you wrote:

 	  Quote: 	
		  



With Z-14 normally running with isolated alternators, I have instant 

notification of either alternator failing due low voltage. With 

paralleled alternators I presume you would add something like low 

current warnings (independent of the regulator) to warn of a bad alternator.

Ken


	


   The B&C alternator controllers were designed such that

   LV warning is powered independently of the lead that

   powers the alternator. The idea was to maintain as much

   separation as possible between jelly-bean parts that

   "regulate" as those which "warn".



   Newer designs with micro-controllers often tempt the

   designer to roll it all up in one piece of silicon.

   The legacy design goals for separation suggest this

   is not a good idea. So even if we were to develop

   a processor based regulator, the OV/LV protection

   and warning would still be electrically independent

   even if they shared the same enclosure.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Aug 03, 2009 6:58 am Post subject: Load Monitoring

At 12:53 PM 8/2/2009, you wrote:

 	  Quote: 	
		  



Bob,



I really appreciate your insight into this stuff.  I'm not just 

"kicking the tires" but really plane some installation in the near 

future and I'm just getting stuff lined up...


	


   Understand.

 	  Quote: 	
		  Regarding the PP regulators, I'm sure Les said that alternators of 

dissimilar outputs would load share based upon their respective max 

values...If, for example, you used the 20/60 amp combo and required 

40 amps, each alternator would be tasked with 50% of the load...but 

I'll check into it...I believe he said that it could be done by each 

regulator being fired up for the same amount of time...does that 

make sense to you?


	


   sort of . . . but given my limited knowledge of

   their design's inner workings, I'd be out of school

   to offer well considered opinion.



 	  Quote: 	
		  I'm not sure why that would work, but I'm pretty sure that's what he 

said was the basis for the idea.  I believe both regulators are 

connected by a single wire that gives the feedback of them "knowing" 

how long to stay on.


	


   This description suggests something of a synchronization

   signal that causes the duty-cycle regulators to do some

   sort of cooperative activity. But this is a kind of

   "feed forward" or "open loop" control philosophy that

   depends on or assumes certain things about the alternator

   characteristics and operation.



   The system may well have performed to design goals in

   PP's testing and field experience with what ever

   combinations of alternators were tried. My personal

   experience suggests that the universal, "feed back" design

   doesn't care about speeds, sizes or transfer functions.

   It does the tight-wire balancing act by monitoring

   actual alternator output as a proportion of total.



 	  Quote: 	
		  Probably my final question on this topic:  If more current is needed 

from an alternator than it is able to make, what happens?


	


   Field voltage is max'd out. The regulator is turned on

   hard. Now the alternator goes into a current limited

   mode based on its physics and depending on how gross

   the overload is, the bus voltage begins to sag.



 	  Quote: 	
		  I expect that most of these alternators will produce more than the 

rated current.  At PP they told me that the 60 amp will easily put 

out more than 70.  I'm not advocating that anyone try it, and I 

expect there are a lot of bad things that would happen if one tried 

to do it for a long time.  Excess heat and premature failure are two 

things I can think of, or even catastrophic failure of the 

unit...what I'm wondering is...what would occur  if, say, the 60 amp 

unit failed and only the 20 amp unit stayed on line when the overall 

requirement was 50 amps.


	


   You've touched on a small segment of the failure

   modes considered for crafting your design. Paralleling

   two alternators makes it difficult to tell when one

   has failed unless the system is ALSO fitted with

   gross imbalance detection and warning in addition to low

   voltage warning. Making the two systems independent

   of each other builds a solid partition between both

   flight operations and failure detection.



   If you had 50 amps being sucked from a 70A paralleled

   system, the smaller alternator would go into current

   limit and it's output sag until the battery picks up

   the difference. I.e. bus voltage drops below 13.0 volts

   and the battery joins the defence to keep the panel

   lit up until (1) you become aware of the condition

   and (2) react to it with a plan-b activity. But

   nothing "smokes". In fact, a properly installed

   alternator is essentially overload-proof. People

   who have burned alternators up didn't "overload" them

   with respect to their ratings . . . they "under-cooled"

   them such that ratings could not be met without

   over heating.



   There's been much past discussion here on the List

   about "de-rating" alternators to prevent bad-days

   in the cockpit. The ratings are what the ratings are.

   Continuous loading at or even past the nameplate ratings

   without electrical damage . . . as long as you get the

   heat out. We routinely TEST as-installed generators and

   alternators to this design philosophy in TC aircraft.



 	  Quote: 	
		  Would the 20 amp unit continue to do it's job to the best of it's 

ability, with the battery(s) picking up the slack for as long as 

they could, or would something worse happen?


	


 	  Quote: 	
		  I'm wondering as this could be the situation IF the 60 amp unit 

failed and one continued with the 20.  I expect I could get by 

indefinitely on the 20 as long it's pitot heat and/or lights were 

needed...just wondering if when that occurred, what would happen.



I suspect that the alternator would do what it could and that the 

battery(s) would pick up the slack with the buss voltage going down 

from 13.8-14 to whatever voltage the batteries could 

supplement...like 12.2  something...



What do you think?

   Yup, you've figured it out. Your well maintained battery
	


   steps in to hold the gremlins at bay until you can

   react to the warnings.



 	  Quote: 	
		  Sorry if this is an old question, but I'm new to the forum and 

didn't find anything with a search.


	


   No problem sir. Out of 1800 other folks who frequent this

   list, there's a bunch who haven't heard this before either.

   This is a classroom, not a one-shot reference library.



   Bob . . .

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