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Question about an Aux Alternator

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melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Wed Sep 26, 2007 12:55 pm Post subject: Question about an Aux Alternator

Hi all:



This is my first post to this list. Do I get a prize?



I have a couple of questions regarding how to go about wiring up my alternator and my Aux Alt. I want to simplify the Nuckolls "all electric airplane" since 1) I'm building a VFR airplane and 2) the only reason I'm even considering an Aux Alt is that it already is installed in the used engine I bought. Specifically, I would like to eliminate the LR-3 Alternator Controller.



Issue 1: It it ok to leave both the aux alt and the main alt in the ON position during flight? I would think that the outputs act much like batteries in parallel so there shouldn't be an issue right?



Issue 2: Is it permissible to wire the output of both alternators to a single shunt? I would like my ammeter to read the output of both alternators as a system. I would check the output of each alternator during start up by turning off each and checking the ammeter. If the main alternator goes off line in flight, I will have an idiot light come on. My ammeter will still show output but with the light on, I'll know that power is coming from the Aux and not the main.



Issue 3: As far as determining the exact wiring diagram to use, can I just treat each system as a separate system? In other words, can I use, for instance, the Aux Alt side of the electric airplane figure in the Nuckolls book and pair it with a simplified main alt layout?



Thanks



Kelly Johnson

RV-9A in progress

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 26, 2007 2:38 pm Post subject: Question about an Aux Alternator

At 01:55 PM 9/26/2007 -0700, you wrote:



 	  Quote: 	
		  



Hi all:



This is my first post to this list. Do I get a prize?



I have a couple of questions regarding how to go about wiring up my 

alternator and my Aux Alt. I want to simplify the Nuckolls "all electric 

airplane"


	


   Keep in mind that these drawings have been distilled down

   over the past 10-20 years to minimize parts count, installation

   and operating complexity while maintaining a favorable failure

   mode effects analysis.

 	  Quote: 	
		  since 1) I'm building a VFR airplane and 2) the only reason I'm even 

considering an Aux Alt is that it already is installed in the used engine 

I bought.


	


    Which alternator is installed?



 	  Quote: 	
		    Specifically, I would like to eliminate the LR-3 Alternator Controller.


	


   For which alternator?

 	  Quote: 	
		  Issue 1: It it ok to leave both the aux alt and the main alt in the ON 

position during flight? I would think that the outputs act much like 

batteries in parallel so there shouldn't be an issue right?


	


   How will you be notified if one of the alternators

   fails?



 	  Quote: 	
		  Issue 2: Is it permissible to wire the output of both alternators to a 

single shunt? I would like my ammeter to read the output of both 

alternators as a system. I would check the output of each alternator 

during start up by turning off each and checking the ammeter. If the main 

alternator goes off line in flight, I will have an idiot light come on.


	


   If you have both alternators on line all the time AND

   the aux alternator is being controlled by an SB-1 regulator,

   then normal operating modes call for both alternators to

   be on all the time but the aux alternator is set for about 1

   volt lower. Hence, while the main alternator is working, the

   aux alternator relaxes and the SB-1's annunciator light is dark.



   If the main alternator fails, but bus votlage sags and the

   aux alternator picks up the loads. If the load exceeds 20A

   the annunciator flashes until you shed loads to some value

   below 20A wereupon the light stop flashing. This is Figure

   Z-12 but with the SB-1 regulator not being substitutable.



 	  Quote: 	
		    My ammeter will still show output but with the light on, I'll know that 

 power is coming from the Aux and not the main.


	


   Why worry about the ammeter at all? You have some

   more rudimentary architecture and operating protocols

   to figure out. The elegant solution doesn't even call

   for an ammeter.



 	  Quote: 	
		  Issue 3: As far as determining the exact wiring diagram to use, can I just 

treat each system as a separate system? In other words, can I use, for 

instance, the Aux Alt side of the electric airplane figure in the Nuckolls 

book and pair it with a simplified main alt layout?


	


   Now I'm totally lost. You began with a discussion of the

   "all electric" (on a budget) which would be Z-13/8 but mentioned

   and LR-3 regulator which suggests an SD-20. Don't know what

   your vision is for the separation between systems.



   Let's begin with a list of the hardware you have in hand

   or expect to use. What kind of alternators, what kind of

   regulators? Now, pick one of the z-figures that comes

   close to what you think you'd like to craft and lets go

   from there.



   Bob . . .

melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Wed Sep 26, 2007 3:07 pm Post subject: Re: Question about an Aux Alternator

Hi Bob:



The main alternator will be a Plane Power 60 A. The Aux Alt is one of those SD-8s. The regulator supplied with it I presume is one that was purchased with the alternator. I'm not a home at the moment so I can't check the specific model number, but I will.



I would like to eliminate the controller for either alternator. I'm hoping that the built in OV protection in the Plane Power will be sufficient for that one. I'm hoping to use the idiot light function in that alternator as well for only that alternator. There is no need to have a light for the aux alt in my case.



My thought about knowing if there is a failed alternator in flight is as follows:



1-If the Aux alt fails, I will not know nor do I care. I'm flying VFR and the Aux Alt is only there because it came with the engine. I can, however, check each alts function on the ground before every take off by 1) watching the idiot light go out which tells me the main alt is functioning and 2) by shutting down the main alt and then enabling the Aux. If the ammeter shows a current, I have a good alternator. Right?



2-If the main alt fails, the idiot light comes on but the ammeter will not show a discharge if 1) the aux alt has enough current to keep up with the load and 2) I can in fact wire both alts to the same shunt. 



As far as you being totally lost, that makes two of us! I'm trying to understand all this. 



From what I gather from the All Electric Airplane is that the intention is to have a seamless switch from the main alt to the aux. Maybe I'm wrong here. For my situation, I don't necessarily need seamless. I'm perfectly fine with having to throw a switch to activate the back up.



I will look again at the various examples in the book, will pick one, and go from there.



The reason for leaving out the LR-3 controller is once again the fact that had the engine not come with an aux alt, I wouldn't even be using one. If it's going to cost me hundreds of dollars to make it function, I'll take it out and put a plate over the hole.



Thanks!



Kelly

melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Wed Sep 26, 2007 4:55 pm Post subject: Re: Question about an Aux Alternator

Hi again Bob:



I do in fact have a B&C regulator.



Let's use Figure Z-13 as the baseline. Two changes I would like to make:



1-Wire both alternators to a single shunt.



2-Eliminate the LR-3.



KJ

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 26, 2007 5:22 pm Post subject: Question about an Aux Alternator

At 05:55 PM 9/26/2007 -0700, you wrote:



 	  Quote: 	
		  



Hi again Bob:



I do in fact have a B&C regulator.



Let's use Figure Z-13 as the baseline. Two changes I would like to make:



1-Wire both alternators to a single shunt.



2-Eliminate the LR-3.



KJ


	


     Which aux alternator do you have? If an SD-8 why not

     wire exactly like Z-13/8 and forget the shunts completely

     or put a shunt in the main alternator only. When you're operating

     from the SD-8, your loads are KNOWN and PREDICTABLE. There's

     good reasons for wiring as shown. See description for Z-13

     on page 3 of



http://aeroelectric.com/articles/Rev11/AppZ_R11K.pdf



     You can use any other combination of voltage regulator,



http://www.aeroelectric.com/Pictures/Regulators/Ford_SS_Reg.jpg



     ov protection



http://www.aeroelectric.com/Pictures/Products/OVM-14_C.jpg



     and low voltage warning



http://www.aeroelectric.com/Pictures/Products/9005_OBS/9005.jpg



     to replace an LR3 . . . but if you already have

     one, why do you want to replace it?



     Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 26, 2007 5:53 pm Post subject: Question about an Aux Alternator

At 04:07 PM 9/26/2007 -0700, you wrote:



 	  Quote: 	
		  



Hi Bob:



The main alternator will be a Plane Power 60 A. The Aux Alt is one of 

those SD-8s. The regulator supplied with it I presume is one that was 

purchased with the alternator. I'm not a home at the moment so I can't 

check the specific model number, but I will.


	


    Aha! I've responded to what may have been an earlier post

    of yours. Disregard. Okay, a PP/60 and SD-8. You don't

    need the LR-3 and in fact it's not even useable with this

    combination. You still need active notification of low voltage.

 	  Quote: 	
		  I would like to eliminate the controller for either alternator. I'm hoping 

that the built in OV protection in the Plane Power will be sufficient for 

that one.


	


   yes



 	  Quote: 	
		    I'm hoping to use the idiot light function in that alternator as well 

 for only that alternator.


	


   no . . . the inadequacy of the built in alternator

   failure warning has been discussed at length here on the

   List. I recommend separate, independent notification of

   low voltage.



 	  Quote: 	
		    There is no need to have a light for the aux alt in my case.


	


   Nor is one shown on Z-13 . . .

 	  Quote: 	
		  My thought about knowing if there is a failed alternator in flight is as 

follows:



1-If the Aux alt fails, I will not know nor do I care. I'm flying VFR and 

the Aux Alt is only there because it came with the engine. I can, however, 

check each alts function on the ground before every take off by 1) 

watching the idiot light go out which tells me the main alt is functioning 

and 2) by shutting down the main alt and then enabling the Aux. If the 

ammeter shows a current, I have a good alternator. Right?



2-If the main alt fails, the idiot light comes on but the ammeter will not 

show a discharge if 1) the aux alt has enough current to keep up with the 

load and 2) I can in fact wire both alts to the same shunt.



As far as you being totally lost, that makes two of us! I'm trying to 

understand all this.


	


   There are good reasons why Z-13 is crafted the way it is for

   both active notification of low voltage and orderly step down

   to 8A e-bus loads in case of main alternator failure. The independent

   shunts offer ability to pre-flight each alternator independently of

   the other.



 	  Quote: 	
		   >From what I gather from the All Electric Airplane is that the intention 

 is to have a seamless switch from the main alt to the aux. Maybe I'm 

 wrong here. For my situation, I don't necessarily need seamless. I'm 

 perfectly fine with having to throw a switch to activate the back up.


	


    Don't know what you consider "seamless".  The multi-layered

    architecture provides means by which all equipment is pre-flight

    testable, offers adequate notification of certain failures in flight

    and places enough separation between layers that no single failure

    of plan-A (or plan-B) precipitates down into the their respective

    subordinate plans.



 	  Quote: 	
		  I will look again at the various examples in the book, will pick one, and 

go from there.



The reason for leaving out the LR-3 controller is once again the fact that 

had the engine not come with an aux alt, I wouldn't even be using one. If 

it's going to cost me hundreds of dollars to make it function, I'll take 

it out and put a plate over the hole.


	


   I'm not sure what this means. The SD-20 aux alternator is usually

   shipped with an SB-1 regulator. If the LR-3 came with your engine,

   it was probably intended for use with some alternator other than

   the SD-20. If you already have an SD-8, then do you have the rectifier

   regulator that goes with it? See:



http://www.aeroelectric.com/Pictures/Alternators/sd8.jpg



   The PlanePower will have its own regulator and ov protection

   so the only thing you are missing is independent notification

   of low voltage. Obviously you can wire your airplane any

   way you wish but the Z-figures as published represent my best

   recommendations for their respective applications. If I were

   building an airplane today, it would have Z-13/8 in it.



   Bob . . .

mprather(at)spro.net
Guest

Posted: Wed Sep 26, 2007 6:07 pm Post subject: Question about an Aux Alternator

Run both alternator b-leads through one hall effect sensor - (requires a

controller circuit or different kind of ammeter)?

Regards,



Matt-



 	  Quote: 	
		   

 <nuckolls.bob(at)cox.net>



 At 05:55 PM 9/26/2007 -0700, you wrote:



>

> <aeroncaflyer(at)gmail.com>

>

>Hi again Bob:

>

>I do in fact have a B&C regulator.

>

>Let's use Figure Z-13 as the baseline. Two changes I would like to make:

>

>1-Wire both alternators to a single shunt.

>

>2-Eliminate the LR-3.

>

>KJ



      Which aux alternator do you have? If an SD-8 why not

      wire exactly like Z-13/8 and forget the shunts completely

      or put a shunt in the main alternator only. When you're operating

      from the SD-8, your loads are KNOWN and PREDICTABLE. There's

      good reasons for wiring as shown. See description for Z-13

      on page 3 of



 http://aeroelectric.com/articles/Rev11/AppZ_R11K.pdf



      You can use any other combination of voltage regulator,



 http://www.aeroelectric.com/Pictures/Regulators/Ford_SS_Reg.jpg



      ov protection



 http://www.aeroelectric.com/Pictures/Products/OVM-14_C.jpg



      and low voltage warning



 http://www.aeroelectric.com/Pictures/Products/9005_OBS/9005.jpg



      to replace an LR3 . . . but if you already have

      one, why do you want to replace it?



      Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Wed Sep 26, 2007 6:19 pm Post subject: Question about an Aux Alternator

At 08:02 PM 9/26/2007 -0600, you wrote:



 	  Quote: 	
		  



Run both alternator b-leads through one hall effect sensor - (requires a

controller circuit or different kind of ammeter)?


	


    That works! I have a number of readers who have done

    just that. Of course, the hall effect ammeter needs to

    run from the e-bus so that it is ALWAYS active under

    any operating condition.



    Bob . . .

andrewbutler(at)ireland.c
Guest

Posted: Thu Sep 27, 2007 4:07 am Post subject: Question about an Aux Alternator

Hi Bob,



Do you supply the AEC9005? I don't see it on your website



Can this module be used to monitor the voltage on the Endurace bus powered by an SD-8 during main alt out? I know that the load is supposed to be predictible, but lets say I wanted to use the AEC9005 to check the SD-8 during pre-flight checks?



Andrew.

 

 [quote]---

nuckolls.bob(at)cox.net
Guest

Posted: Thu Sep 27, 2007 4:51 am Post subject: Question about an Aux Alternator

At 12:04 PM 9/27/2007 +0000, you wrote:



 	  Quote: 	
		  Hi Bob,



Do you supply the AEC9005? I don't see it on your website


	


    It's slated to be replaced by the AEC9011 later this year

    and there are other suppliers of similar products.

 	  Quote: 	
		  Can this module be used to monitor the voltage on the Endurace bus powered 

by an SD-8 during main alt out?


	


    Yes, in fact I have some builders who have used the lv warning

    system to do selective load shedding (clumsy but it works). Keep

    turning things off until the lv warning light stays out. It's

    far better to have plan-b loads pre-selected and part of your

    alternator-out ops checklist.



 	  Quote: 	
		    I know that the load is supposed to be predictible, but lets say I wanted to

  use the AEC9005 to check the SD-8 during pre-flight checks?


	


    Yes, but the "test" may be time-dependent . . . and it

    presupposes that total loads on the system do not exceed

    the SD-8 output capability at pre-flight run-up speeds.

    Far better that you sense the output current and simply

    observe that the SD-8 picks up a load irrespective of

    bus voltage and system loads. Does your system have any

    other voltmeter functions in it? For example, with minimum

    loads on system, when you turn the main alternator off

    and the SD-8 on, any rise in bus voltage no matter

    how slight is a good indication that the SD-8 is alive

    and well.



    Bob . . .



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

        ( "Problems are the price of progress. )

        ( Don't bring me anything but trouble. )

        ( Good news weakens me."               )

        (              -Charles F. Kettering-  )

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

melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Thu Sep 27, 2007 7:35 am Post subject: Re: Question about an Aux Alternator

I do indeed have the rectifier regulator...at least what I have looks like the one in the picture Bob linked. There is no number on it.



I don't physically have the LR-3. I was referring to it in regards to the Z-13. 



Regarding the hall effect sensor comment. I'm running a Dynon FlightDEK-D180 as my main instrument. It has the ability to read current and voltage. In its manual, it states that for current, I have the option to use the GRT CS-01 hall effects sensor. So running both B leads through this sensor will do what I'm looking to do and that is to read the current of both alternators combined. The reason for this is that I don't want to have a separate ammeter for the aux alternator. I want it all to go through the Dynon. I suppose I could have some sort of selector switch set up to determine which alternator the Dynon is displaying as well right?



I don't think I ever got an answer on this one: Is it not a good idea to run both alternators to a single shunt?



Bob has commented that the SD-8 has known qualities and suggested that a case can be made for not using an ammeter for it. I personally want the ability to look at the output in flight. If a light comes on I'd like to have a warm fuzzy that the SD-8 is indeed putting out.



OK, to sum it up, this is what I understand:



1-Yes, the LR-3 can be replaced in the Z-13 diagram by the Plane Power alternator because its built in OV protection circuit is adequate.



2-Bob says that the Plane Power alternator warning light output is not recommended and that a separate warning system per Bob's book should be used.



3-Normal operation would be to run both alternators simultaneously because the rectifier regulator for the aux is set for 1 volt lower and will relax during normal operation. 



Do I understand this correctly?

frank.hinde(at)hp.com
Guest

Posted: Thu Sep 27, 2007 7:57 am Post subject: Question about an Aux Alternator

I bought 2 shunts and a mini double pole (on-on) switch from radio

shack. Th panel is labelled "alt1/2" and the output of the switch wired

to the Dynon.



I can simply select which alt I wish to measure that way.



Frank

RV7a 



--

mprather(at)spro.net
Guest

Posted: Thu Sep 27, 2007 8:40 am Post subject: Question about an Aux Alternator

A shunt is used to measure current in a wire by inserting a known, small

resistance in that wire.  A meter is wired across this known resistance. 

The reading on the meter is calibrated to show current based on how much

voltage is dropped across the shunt.  Man shunts are at full scale with a

50mV drop.



In order to run to a single shunt on both alternators, the output of the

alternators would need to be hard wired together.  Certain fail modes on

one alternator might lead to the other alternator not being able to

generate any output.  Additionally, having both alternators wired together

may make regulation a challenge.



If you'd like to use shunt vice hall effect, I propose that you use two

shunts and then add a switch so that you can select which is driving your

instrumentation.

Regards,



Matt-

 	  Quote: 	
		   

 <aeroncaflyer(at)gmail.com>



 I do indeed have the rectifier regulator...at least what I have looks like

 the one in the picture Bob linked. There is no number on it.



 I don't physically have the LR-3. I was referring to it in regards to the

 Z-13.



 Regarding the hall effect sensor comment. I'm running a Dynon

 FlightDEK-D180 as my main instrument. It has the ability to read current

 and voltage. In its manual, it states that for current, I have the option

 to use the GRT CS-01 hall effects sensor. So running both B leads through

 this sensor will do what I'm looking to do and that is to read the current

 of both alternators combined. The reason for this is that I don't want to

 have a separate ammeter for the aux alternator. I want it all to go

 through the Dynon. I suppose I could have some sort of selector switch set

 up to determine which alternator the Dynon is displaying as well right?



 I don't think I ever got an answer on this one: Is it not a good idea to

 run both alternators to a single shunt?



 Bob has commented that the SD-8 has known qualities and suggested that a

 case can be made for not using an ammeter for it. I personally want the

 ability to look at the output in flight. If a light comes on I'd like to

 have a warm fuzzy that the SD-8 is indeed putting out.



 OK, to sum it up, this is what I understand:



 1-Yes, the LR-3 can be replaced in the Z-13 diagram by the Plane Power

 alternator because its built in OV protection circuit is adequate.



 2-Bob says that the Plane Power alternator warning light output is not

 recommended and that a separate warning system per Bob's book should be

 used.



 3-Normal operation would be to run both alternators simultaneously because

 the rectifier regulator for the aux is set for 1 volt lower and will relax

 during normal operation.



 Do I understand this correctly?





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=136778#136778

melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Thu Sep 27, 2007 8:50 am Post subject: Re: Question about an Aux Alternator

Thanks! The switch is a great idea but how about this?



I'm really more interested in what is going in and out of the battery. I want to know if it is charging or discharging. If it's charging, I don't necessarily care where the juice is coming from. My idiot lights will tell me if my main alt is inop anyway.



So, what if I eliminate the two shunts as depicted in Figure Z-13 and put one in the appropriate line leading eventually to the battery but not in the starter circuit? That should do what I'm looking for right?

frank.hinde(at)hp.com
Guest

Posted: Thu Sep 27, 2007 9:20 am Post subject: Question about an Aux Alternator

Sure that will work, I believe that's one of the ways Dynon suggests you

wire up the shut anyway.



It is debatable whether you even need an ammeter at all..I.e if you set

your low voltage alarm for 12v and use the Dynon audible output then you

know when you have a low battery voltage and therefore a malfunctioning

alternator.



I don't honestly remember when I had to use my ammeter, even when I did

an operational check of my SD8...I just knew the batt voltage alarm went

off when I hit the transmit button...



Cheers



Frank



--

nuckolls.bob(at)cox.net
Guest

Posted: Thu Sep 27, 2007 1:43 pm Post subject: Question about an Aux Alternator

 	  Quote: 	
		  

I don't physically have the LR-3. I was referring to it in regards to the 

Z-13.


	


   The Z-figures are to suggest ARCHITECTURE only, there are a host

   of alternator, regulator, ov-protection, lv-warning combinations

   that will happilly integrate into the Z-13 archtecture.



 	  Quote: 	
		  Regarding the hall effect sensor comment. I'm running a Dynon 

FlightDEK-D180 as my main instrument. It has the ability to read current 

and voltage. In its manual, it states that for current, I have the option 

to use the GRT CS-01 hall effects sensor. So running both B leads through 

this sensor will do what I'm looking to do and that is to read the current 

of both alternators combined. The reason for this is that I don't want to 

have a separate ammeter for the aux alternator. I want it all to go 

through the Dynon. I suppose I could have some sort of selector switch set 

up to determine which alternator the Dynon is displaying as well right?


	


   If you have a voltage reading on the display, then you

   can live quite happily with no shunts whatsoever.

 	  Quote: 	
		  I don't think I ever got an answer on this one: Is it not a good idea to 

run both alternators to a single shunt?


	


   Only if your willing to abandon the features depicted

   in the Z-figures. There are reasons why they'll crafted

   as shown. You can certainly depart in any manner you choose

   and you will no doubt achieve some level of functionality.

   But it's up to you to decide if that's what you want.



   I get dozens of emails every month extolling the virtus

   of one z-figure or another followed by a narrative of all

   the things the writer wants to change and wants me to

   somehow bless the changes.



   I don't have the time to take on another consulting

   task and it's doubtful that the writer would want to

   pay my outrageous fees. Further, he's at risk that

   I would still recommend that he stay with one of

   the z-figures and then bill him for the advice.



   So please understand that I'm not trying to be a hard-ass

   on some sort of not-invented-here syndrome. I'm only

   pointing out that what you see is what you get and the

   price is certainly right. If your personal requirements

   depart from the recommendations, that's fine with me

   but please don't expect me to spend a lot of time either

   supporting or trying to dissuade you from making the

   changes.



   Bob . . .

nuckolls.bob(at)cox.net
Guest

Posted: Sat Sep 29, 2007 8:04 pm Post subject: Question about an Aux Alternator

At 08:35 AM 9/27/2007 -0700, you wrote:



 	  Quote: 	
		  



I do indeed have the rectifier regulator...at least what I have looks like 

the one in the picture Bob linked. There is no number on it.



I don't physically have the LR-3. I was referring to it in regards to the 

Z-13.


	


  Okay, if you use a generic, externally regulated alternator

  the you need the equivalent of the LR-3 in the three components

  I illustrated.

 	  Quote: 	
		  



Regarding the hall effect sensor comment. I'm running a Dynon 

FlightDEK-D180 as my main instrument. It has the ability to read current 

and voltage. In its manual, it states that for current, I have the option 

to use the GRT CS-01 hall effects sensor. So running both B leads through 

this sensor will do what I'm looking to do and that is to read the current 

of both alternators combined. The reason for this is that I don't want to 

have a separate ammeter for the aux alternator. I want it all to go 

through the Dynon. I suppose I could have some sort of selector switch set 

up to determine which alternator the Dynon is displaying as well right?



I don't think I ever got an answer on this one: Is it not a good idea to 

run both alternators to a single shunt?


	


   To do so departs from the architecture described in Z-13.

   But you could use a single hall effect sensor for both

   alternator feeds. The hall effect measures current in each

   wire independently and does not disturb the recommended

   architecture.



 	  Quote: 	
		  Bob has commented that the SD-8 has known qualities and suggested that a 

case can be made for not using an ammeter for it. I personally want the 

ability to look at the output in flight. If a light comes on I'd like to 

have a warm fuzzy that the SD-8 is indeed putting out.


	


   If the SD-8 is working, the lv warn light goes out.



 	  Quote: 	
		  OK, to sum it up, this is what I understand:



1-Yes, the LR-3 can be replaced in the Z-13 diagram by the Plane Power 

alternator because its built in OV protection circuit is adequate.


	


   Not quite. The LR-3 is designed for use in conjunction

   with an externally regulated alternator, NOT a PlanePower

   product which has its own, built in regulation and ov

   protection.

 	  Quote: 	
		  2-Bob says that the Plane Power alternator warning light output is not 

recommended and that a separate warning system per Bob's book should be used.


	


   That's the recommendation.

 	  Quote: 	
		  3-Normal operation would be to run both alternators simultaneously because 

the rectifier regulator for the aux is set for 1 volt lower and will relax 

during normal operation.


	


   No, Figure Z-13 is a two layer system set up to back up the

   main alternator driving the main bus with an SD-8 alternator

   driving an e-bus.

 	  Quote: 	
		  Do I understand this correctly?


	


   The autoswitch feature I described is UNIQUE to Z-12 with

   an SD-20 alternator and SB-1 regulator driving the main

   bus and set up like the STC used to put this system on

   a host of TC aircraft.



   With Z-13, you leave the SD-8 off until needed when

   it is determined that the main alternator is off line

   (lv light on). You drop to e-bus loads, open battery

   contactor, turn SD-8 on and continue to airport of

   intended destination. If the SD-8 is not overloaded,

   the lv warning light will go back out.



   Bob . . .

Paul Valovich

Joined: 11 Jan 2006
Posts: 75

Posted: Mon Oct 01, 2007 8:37 am Post subject: Question about an Aux Alternator

A different aux alt question:  

   

Rv-8A QB Z-13/8 with a continuous main bus load of 21 amps and an intermittent max load of 28 amps. I initially was going to use a B&C 60 amp alternator and an SD-8, but got to thinkin’ that a 40 amp alt would be sufficient. If the SD-8 is continuously on, wouldn’t it pick up any intermittent loads (up to 8 amps) above the main alternator max limit ?  

Paul Valovich  

N192NM Reserved (Again)  

      [quote][b]

nuckolls.bob(at)cox.net
Guest

Posted: Mon Oct 01, 2007 7:21 pm Post subject: Question about an Aux Alternator

At 12:36 PM 10/1/2007 -0400, you wrote:



 	  Quote: 	
		  A different aux alt question:



Rv-8A QB Z-13/8 with a continuous main bus load of 21 amps and an 

intermittent max load of 28 amps. I initially was going to use a B&C 60 

amp alternator and an SD-8, but got to thinkin that a 40 amp alt would be 

sufficient. If the SD-8 is continuously on, wouldn t it pick up any 

intermittent loads (up to 8 amps) above the main alternator max limit ?


	


   The 40A would be fine all by itself. This still gives you plenty

   of headroom to recharge a battery.



   The SD-8 generally should not be used to "boost" total

   output and in the case you've cited above, isn't

   necessary.



   Bob . . .



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

        ( "Problems are the price of progress. )

        ( Don't bring me anything but trouble. )

        ( Good news weakens me."               )

        (              -Charles F. Kettering-  )

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

melkel2000

Joined: 26 Sep 2007
Posts: 6

Posted: Tue Oct 02, 2007 6:50 am Post subject: Re: Question about an Aux Alternator

"With Z-13, you leave the SD-8 off until needed when 

it is determined that the main alternator is off line 

(lv light on). You drop to e-bus loads, open battery 

contactor, turn SD-8 on and continue to airport of 

intended destination. If the SD-8 is not overloaded, 

the lv warning light will go back out."



With regards to the SD-8 and the lv light, Z-13 has a single lv light on the diagram. The descripton for the PV/OV crows foot kit available from B and C states that "The PM/OV was designed to give over voltage protection to the permanet magnet alternator. The yellow light will annunciate if the alternator switch is left off, or the crowbar over voltage protection has been tripped. " 



So, will the single lv light depicted on Z-13 light if either the main alt or the SD-8 are off line?



If the SD-8 has its own unique lv light as described on the B and C site, does it light if the aux alt selection switch is OFF? Or, does it only light if the aux alt selector switch is ON AND the SD-8 is off line? If the first case is true, during normal operation, the aux lv light will alway remain lit which would not be an ideal situation.



Thanks



Kelly

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