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hotwheels

Joined: 01 Jun 2007
Posts: 240

Posted: Sat Feb 09, 2008 9:14 pm Post subject: Know Your Charging System article

I recently ran across this article regarding aircraft alternator operation and charging systems.



http://www.nflite.com/ChargingSystem.html



If you scroll down past the general explanations, there is a section titled "Don't overload the system!". 



The short story is that the author recommends starting the engine with ALT field off so as to not overload the charging system and/or put undue strain on the diode rectifier. Is there anything to this theory? 



Regards,

Jay

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Sun Feb 10, 2008 4:54 am Post subject: Know Your Charging System article

This ARTICLE is for Externally Regulated Alternators!

   

  Jay great article and I agree with it 100%, but it's for 

EXTERNALLY REGULATED AIRCRAFT ALTERNATORS

ONLY. JUST A FYI.

   

    The part about no OVER LOADING applies to all 

  alternators, but the part about SWITCH throwing is 

  not good for all alternators.



   

  Their suggestion is to:

   

  1) Leave the alternator switch OFF BEFORE starting 

the engine.

   

  2) Turn the alternator switch ON AFTER the engine is 

running.

   

  This CAN AND HAS DAMAGED Internal-Voltage Regulated 

Alternators (I-VR).

   

  I-VR ALTERNATORS LIKE A NIPPONDENSO, which 

are popular with the, kit-plane, home-building, 

amateur/experimental community are a totally different 

deal. This is  the problem, people try to apply old 

time E-VR ideas to I-VR and get in trouble. It's a 

whole new ball game.

   

  I-VR alternators are designed to be ON before engine 

start. They have a soft start function in their "brain" or IC 

chip controller.

   

  I-VR alternators are made to STAY ON during engine 

shut down. Again it knows when to knock off work.

   

  Some say it does not matter, but I have seen a 

correlation between I-VR failures and pilots that do the 

switch throwing procedure while the engine is turning. 

   

  It's real simple, ALT ON with master BEFORE start, 

  ALT OFF with master AFTER shut down. 

   

  Look at an auto-repair manual for cars; you will see 

how the KEY operation works in regards to the 

alternator. Over riding the AUTO function of the IC 

controller inside a  I-VR is not necessary or desirable.

   

  Cheers George

   

   

  >Subject: Know Your Charging System article

 	  Quote: 	
		  From: "jayb" <jaybrinkmeyer(at)yahoo.com (jaybrinkmeyer(at)yahoo.com)>

   
	


  >I recently ran across this article regarding aircraft 

 	  Quote: 	
		  alternator operation >and charging systems.

   
	


  http://www.nflite.com/ChargingSystem.html

   

  >If you scroll down past the general >explanations, 

 	  Quote: 	
		  there is a section titled "Don't overload the system!". 

  >The short story is that the author recommends starting 
	


 	  Quote: 	
		  the engine with ALT field off so as to not overload the 

charging system and/or put undue strain on the diode 

rectifier. Is there anything to this theory? 

   
	


   >Regards, Jay



        Be a better friend, newshound, and   [quote][b]

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Sun Feb 10, 2008 5:09 am Post subject: Know Your Charging System article

PS: This statment in the article is faults:

   

  >The ignition switch (in a car) is also cutting off 

  >power to the voltage regulator (which shuts down 

  >the alternator) while the engine is being started.

   

  That is 100% un-true.

   

    To be clear , the power to the IGN lead 

  of I-VR alternators comes on and off with 

  the car's IGNITION. The fact the alternator 

  manufactures label it IGN should be 

  a clue! (you think ha-ha)



   

  This is where people get externally regulated 

  alternators and generator mixed up with modern 

  internally regulate  alternators, which have a 

  controller or IC "brain" to automatically handle 

  the alternators functions. Now I can't say for 

  sure ALL brands work this way, but most 

  modern (since early mid 1980's) NipponDenso 

  alternators work this way. How other brands 

  or knock-off clones of ND alternators work 

  is to be determined (with some simple test 

  and observations.)

   

  Again externally regulated and internally 

  regulated are APPLES and ORANGES, 

  at least when it comes to its "spool up" 

  or powering-up and shut down. 

   

  Cheers George



   [quote][b]

nuckolls.bob(at)cox.net
Guest

Posted: Mon Feb 11, 2008 7:43 pm Post subject: Know Your Charging System article

At 09:14 PM 2/9/2008 -0800, you wrote:



 	  Quote: 	
		  



I recently ran across this article regarding aircraft alternator operation 

and charging systems.



http://www.nflite.com/ChargingSystem.html



If you scroll down past the general explanations, there is a section 

titled "Don't overload the system!".



The short story is that the author recommends starting the engine with ALT 

field off so as to not overload the charging system and/or put undue 

strain on the diode rectifier. Is there anything to this theory?



Regards,

Jay


	


   Yeah, that idea surfaces from time to time. It's

   been promulgated by a lot of folks who don't

   understand the physics of alternator performance.



   I've reviewed the article and posted some comments

   at:



http://www.aeroelectric.com/_temp/Know_Your_Charging_System.pdf





        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Tue Feb 12, 2008 6:56 am Post subject: Know Your Charging System article

Bob Thanks for your typical detailed review of the  

article. You make several good points, but I would like  

to comment on "overload" v. longevity. You seem to  

justify your opinion on certification of alternators (type  

cert. planes), which is not relevant to alternator 

service longevity.

 

Certification is fine, but no guarantee of longevity. For  

example, Lycoming allows Cyl Head Temp (CHT) up to   

500F, red line, but on the side, Lycoming tells pilots if  

you want your engine to last, better keep CHT under  

400F. Lyc doesn't make 2,000 hr TBO (at) 500F or even 

  435F CHT. Lyc cert testing includes full pwr test, but 

  not for a full 2,000 hrs (I think its 20 hours). Bottom 

  line, a cert test is not the way to operate your engine.

  

Same with alternators, it may pass a FAA certification   

test, but that is no guarantee of longevity, at least  

past the test period.

 

I'm one that does subscribe to the unscientific myth that  

running an alternator at full rated load will reduce its life. 

More correctly stated running your alternator HOT all 

the time reduces life. A Gent on this list, retired from the  

automotive electrical engineering field, held the same  

opinion, re-rating aside.

 

In a plane, the alternator is subject to external heat,  

such as exhaust pipes. At high attitude the thin air  

reduces cooling. The more power an alternator is 

trying make, the hotter it runs. Combine all these 

factors, YOU CAN COOK the alternator.

 

Clearly cooling is a big factor. If you have "forced  

cooling" than yes you can run right up to rated power.  

The issue is heat. That's why ND's have TWO fans.

 

HEAT has negative affects on  semiconductors, brushes, 

bearings and the voltage regulator (if on-board). 

It's just common sense. Too much heat = bad.

  

Last, in the electronics industry, its well known there's a 

direct correlation between semi-conductor life (like the 

diodes in the rectifier) and temp. Chance of failure goes 

up,  time between failures goes down, statistically 

with higher temps. I agree modern semiconductors are 

amazingly robust devices, and they are better than past 

components and will be better in the future.

   

  I don't agree with the author's premise that alternators 

in cars should last as long as ones in planes, all thing 

being equal. In airplanes alternators tend to have less 

cooling and more vibrations than in an auto application. 

Also in the auto industry 80, 90, 100, 120 amp 

alternators are now common for passenger cars, not 

because they need all that  power. It's because they are 

de-rated and need to make power when the engine is 

idling at low RPM and to KEEP THEM COOL.

   

  To get more life from alternators increase cooling, 

  shield for head, reduce vibration and oversize the 

  alternator relative to max load (aka de-rating). 

    

  

 	  Quote: 	
		  From: "Robert L. Nuckolls, III" nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net) 

Subject: Re: Know Your Charging System article 

 

> I recently ran across this article regarding aircraft  

> alternator operation and charging systems.  

>  

> http://www.nflite.com/ChargingSystem.html  

>  

> If you scroll down past the general explanations,  

> there is a section titled "Don't overload the  system!".  

> The short story is that the author recommends  

> starting the engine with ALT  field off so as to not  

> overload the charging system and/or put undue  

> strain on the diode rectifier. Is there anything to this  

> theory? 

> 

> Regards, Jay  

  > 
	


   > Yeah, that idea surfaces from time to time. It's  

   > been promulgated by a lot of folks who don't  

   > understand the physics of alternator performance.  

   >  

   >I've reviewed the article and posted some comments at:  

  

http://www.aeroelectric.com/_temp/Know_Your_Charging_System.pdf

   



   [quote][b]

walter.fellows(at)gmail.c
Guest

Posted: Tue Feb 12, 2008 7:28 am Post subject: Know Your Charging System article

Bob

Thanks for taking the time to read and comment on this article. It helps with understanding the system. Have you written a description of the electrical system  that could be used with the drawings for a service manual (including troubleshooting)? I understand your point about a good technician not needing it but this is a less than perfect world and my experience is that many good mechanics are not not that good with electrical systems. It would also be helpful for the owner/builder to more efficiently diagnose problems.

On an unrelated matter, I notice that most of the type certified composite aircraft (columbia, cirrus and diamond) have external antennas. Do you know if this is a requirement for certification? Is there any reason that blind antennas cannot be just as effective as external antennas?

Best Regards

Walter Fellows

On Feb 11, 2008 7:39 PM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

[quote] --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

At 09:14 PM 2/9/2008 -0800, you wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "jayb" <jaybrinkmeyer(at)yahoo.com (jaybrinkmeyer(at)yahoo.com)>

 >

 	  Quote: 	
		  I recently ran across this article regarding aircraft alternator operation

and charging systems.

http://www.nflite.com/ChargingSystem.html

 >

 	  Quote: 	
		  If you scroll down past the general explanations, there is a section

titled "Don't overload the system!".

The short story is that the author recommends starting the engine with ALT

 >field off so as to not overload the charging system and/or put undue

 	  Quote: 	
		  strain on the diode rectifier. Is there anything to this theory?

Regards,

Jay

   Yeah, that idea surfaces from time to time. It's

    been promulgated by a lot of folks who don't

   understand the physics of alternator performance.

   I've reviewed the article and posted some comments

   at:

http://www.aeroelectric.com/_temp/Know_Your_Charging_System.pdf

        Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

  [quote][b]

rampil

Joined: 04 May 2007
Posts: 870

Posted: Tue Feb 12, 2008 8:55 am Post subject: Re: Know Your Charging System article

Walter,



Many certified composite AC have a conductive layer in the composite

to reduce (possibly) the impact of a lightning strike.  Might also reduce

P-static during IFR operatives



Conductive layer -> No RF passage



If you don't have a conductive layer, put your antennae inside and save

yourself a few knots.  The antennae will not know the difference for most

intents and purposes

As for A&Ps knowing avionics or even power circuits, you are right,

there is an incredibly strong inverse correlation between memorization 

of what size wrench to use on an AN-5 bolt and knowledge of how 

ground loops form and how to reduce their effect!



Not a perfect correlation, but pretty darn good 

I have met an exception or two out there

_________________
Ira N224XS

nuckolls.bob(at)cox.net
Guest

Posted: Tue Feb 12, 2008 9:11 am Post subject: Know Your Charging System article

At 06:52 AM 2/12/2008 -0800, you wrote:



 	  Quote: 	
		  Bob Thanks for your typical detailed review of the

article. You make several good points, but I would like

to comment on "overload" v. longevity. You seem to

justify your opinion on certification of alternators (type

cert. planes), which is not relevant to alternator

service longevity.


	


   No such thing. I'm saying that testing confirms

   compliance with published limits. It says nothing about

   the quality of the device. We DO a lot of testing

   in the certified world . . . but precious little in

   the OBAM world.



 	  Quote: 	
		  

Certification is fine, but no guarantee of longevity. For

example, Lycoming allows Cyl Head Temp (CHT) up to

500F, red line, but on the side, Lycoming tells pilots if

you want your engine to last, better keep CHT under

400F. Lyc doesn't make 2,000 hr TBO (at) 500F or even

435F CHT. Lyc cert testing includes full pwr test, but

not for a full 2,000 hrs (I think its 20 hours). Bottom

line, a cert test is not the way to operate your engine.



Same with alternators, it may pass a FAA certification

test, but that is no guarantee of longevity, at least

past the test period.



I'm one that does subscribe to the unscientific myth that

running an alternator at full rated load will reduce its life.

More correctly stated running your alternator HOT all

the time reduces life. A Gent on this list, retired from the

automotive electrical engineering field, held the same

opinion, re-rating aside.



In a plane, the alternator is subject to external heat,

such as exhaust pipes. At high attitude the thin air

reduces cooling. The more power an alternator is

trying make, the hotter it runs. Combine all these

factors, YOU CAN COOK the alternator.


	


   Never said you couldn't . . . All I've said

   is that the user of any product should have

   a reasonable expectation of satisfactory

   service life if the system integrator

   respects operating limits cited in the

   product's data sheets.



   Are you suggesting that alternators in general

   cannot be expected to deliver a satisfactory

   service life unless de-rated or otherwise

   papered in ways not cited by the manufacturer?

   Are you saying that alternators last longer in

   cars because the systems integrators have

   built some form of pampering or de-rating

   into their products?



 	  Quote: 	
		  

Clearly cooling is a big factor. If you have "forced

cooling" than yes you can run right up to rated power.

The issue is heat. That's why ND's have TWO fans.



HEAT has negative affects on semiconductors, brushes,

bearings and the voltage regulator (if on-board).

It's just common sense. Too much heat = bad.



Last, in the electronics industry, its well known there's a

direct correlation between semi-conductor life (like the

diodes in the rectifier) and temp. Chance of failure goes

up,  time between failures goes down, statistically

with higher temps. I agree modern semiconductors are

amazingly robust devices, and they are better than past

components and will be better in the future.



I don't agree with the author's premise that alternators

in cars should last as long as ones in planes, all thing

being equal. In airplanes alternators tend to have less

cooling and more vibrations than in an auto application.

Also in the auto industry 80, 90, 100, 120 amp

alternators are now common for passenger cars, not

because they need all that power. It's because they are

de-rated and need to make power when the engine is

idling at low RPM and to KEEP THEM COOL.


	


    "tend to have less cooling" . . . are you telling

    me that the system integrator purposefully ignored

    or accidently overlooked the manufacturer's operating

    limits? Or perhaps you believe published limits

    are bogus or inaccurate?



    What's KEEP THEM COOL mean? Do you have temperature

    limits to recommend? Where measured? How does one KNOW

    they are doing a good thing? Should I consider

    offering a new product: "Alternator Over-Temp

    Warning Module"?



 	  Quote: 	
		  

To get more life from alternators increase cooling,

shield for head, reduce vibration and oversize the

alternator relative to max load (aka de-rating).


	


     . . .or do good engineering to confirm your

    design is golden before you hand the keys

    to the customer. I don't see where we disagree.

    The end goal is the same whether you're building

    your airplane in the garage or on a factory floor.

    The tests are the same whether you're doing

    a FAR cert plan or a 40-hour fly off on your

    homebuilt.



    If one doesn't KNOW by means of purposeful

    MEASUREMENT that the system is golden,

    then yes, the alternative is subscription

    to any doctrine of faith or uncertainty one

    wishes. The author of the article was speaking

    about certified aircraft and offering a LOT of

    slightly organized, sometimes accurate

    information sprinkled with too many

    inferences and baseless deductions. In

    many cases, the deductions were demonstrably

    wrong.



    The bottom line is that one may choose to

    understand and act on that understanding

    or "go with the flow" of what ever advice

    passes by. The problem is navigating an

    ocean of advice.



    Walking past the front of one of those

    so-called health and nutrition centers in

    a shopping mall, I've oft fantasized about

    walking into the store and saying, "Give me

    one of everything."



    No doubt the clerk would be surprised and

    possibly even curious as to why I would

    make such a request. I'd then offer, "Would

    you agree that all the products in this

    store are offered to be helpful and are

    free of hazard?"



    "Of course."



    "0kay, if one wishes to exploit the benefits

    offered, then the easy approach is to take

    one of everything."



    "But that would be too much . . . what malady

    or health issue are you wanting to address?"



    "Oh, I'm okay . . . or at least I feel okay

    right now, but since you can't practice

    medicine by offering cures, then 100% of

    the products in this store are considered

    a hedge against suffering some future malady."



    "Sure."



    "Okay, what's your advice for preventing

    if not mitigating any or all future

    suffering?"



    Here's where we discover that the store

    is stocked with thousands of competing

    ideas and advice where less than 1% of

    ingredients in all products would be

    truly useful to the target customer.



    In this case the target customer is ignorant

    of the mechanism by which any product

    offers benefit. The customer is concerned

    about lots of things. Every tenth add on TV

    and in magazines is for some kind of pill. Every

    devotee of the store's doctrine and dogma

    willing to extoll the virtues of a variety

    of offered products. Thousands of hopeful

    customers drag their various worries to

    the store hoping their faith in the church

    of bottle-driven health will be rewarded.



    The article is question is the technological

    equivalent of the 10,000 bottle health

    and nutrition store. It's my mission to

    filter the 99% noise and useless (but

    mostly harmless) data so that folks can

    exploit what's left over to advance their

    understanding and the utility of their project.



    Are you suggesting that the readers of this

    List de-rate their alternators and subscribe

    to every maintenance and operating procedure

    offered in every article written about their

    electrical system? Would you agree that

    some filtering of advice is called for? What

    filtering mechanism do you recommend?



    For myself, I find comfort in reliance

    upon experience of myself and my

    colleagues where understanding and

    observation of published limits confirmed

    with good measurement are the path to

    electrical system Nirvana. Service life

    then becomes a quality/performance issue

    that drives a search for manufacturers who

    excel at conducting business in an honorable way.



    Bob . . .

john_rv10(at)yahoo.com
Guest

Posted: Tue Feb 12, 2008 11:35 am Post subject: Know Your Charging System article

Bob's response 



--

nuckolls.bob(at)cox.net
Guest

Posted: Tue Feb 12, 2008 12:40 pm Post subject: Know Your Charging System article

At 07:23 AM 2/12/2008 -0800, you wrote:



 	  Quote: 	
		  Bob



Thanks for taking the time to read and comment on this article. It helps 

with understanding the system. Have you written a description of the 

electrical system  that could be used with the drawings for a service 

manual (including troubleshooting)? I understand your point about a good 

technician not needing it but this is a less than perfect world and my 

experience is that many good mechanics are not not that good with 

electrical systems. It would also be helpful for the owner/builder to more 

efficiently diagnose problems.


	


   See the website at



http://aeroelectric.com/



   where the AeroElectric Connection textbook

   is offered in addition to numerous writings

   downloadable from the website. In particular,

   check out Appendix Z from the text where

   you'll find numerous exemplar alternator

   installations and a troubleshooting procedure

   in the notes section. Note 8 as I recall.

 	  Quote: 	
		  On an unrelated matter, I notice that most of the type certified composite 

aircraft (columbia, cirrus and diamond) have external antennas. Do you 

know if this is a requirement for certification? Is there any reason that 

blind antennas cannot be just as effective as external antennas?


	


   It's a matter of degrees. ANYTHING one puts between

   the antenna and a signal source has an effect on

   performance. From the standpoint of producing an

   installation on a TSO'd system that yields predictable

   airplane to airplane performance, it's best that the

   antenna be mounted outside.



   That's not to say that some ambitious air-framer

   would be told not to cover the antenna up but

   it adds to the certification workload to prove

   that the degradation is acceptable. Hence,

   most folks don't do it.



   Bob . . .

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