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BASIC DUAL POWER SUPPLY

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Mon Apr 30, 2007 3:55 pm Post subject: BASIC DUAL POWER SUPPLY

Hi Gilles,  

Thanks for the insight on the use of a supplementary battery . Is your alternate battery in the charging loop or switched to charge? Can you explain circuit details how you amended Z16 as I need to treat this as a true option?  

   

At the same time it is hard for me to let go of the idea that the self excited alternator is a ready alternate independent power source for the ebus.   

(I hear your caution about the reliability of the Jabiru regulator and may need to source another anyhow as it remains to be seen if the Jab regulator will excite work in Z25)  

I have redrawn the circuit in a more simple arrangement which is now close to the original plans issued for my Quickie but enhanced with the self excitation feature of Z25, the OVM and with the added dual supply circuit feature.  

The DPST master switch has been working OK for 20 years but will benefit from the OVM which I think is essential for protection of the ebus.  

   

But have I shown it in the right place for this protection?  

   

The original plans depend on the master switch to isolate battery from alternator from bus . There are no alternator or battery disconnect relays.  

I see an advantage in using those relays to limit heavy current wiring in the cockpit but I already have the wiring and an amp meter with internal shunt.  

Is there another advantage in the use of these relays ?  

   

Thanks for your patience as I am obviously at the bottom of the learning curve.  

Regards  

Peter      

   

At the same time [img]cid:image001.jpg(at)01C78BD5.D4FC06D0[/img]

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nuckollsr(at)cox.net
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Posted: Tue May 01, 2007 6:10 am Post subject: BASIC DUAL POWER SUPPLY

At 09:49 AM 5/1/2007 +1000, you wrote:



 	  Quote: 	
		  Hi Gilles,



Thanks for the insight on the use of a supplementary battery . Is your 

alternate battery in the charging loop or switched to charge? Can you 

explain circuit details how you amended Z16 as I need to treat this as a 

true option?



At the same time it is hard for me to let go of the idea that the self 

excited alternator is a ready alternate independent power source for the ebus.



(I hear your caution about the reliability of the Jabiru regulator and may 

need to source another anyhow as it remains to be seen if the Jab 

regulator will excite work in Z25)



I have redrawn the circuit in a more simple arrangement which is now close 

to the original plans issued for my Quickie but enhanced with the self 

excitation feature of Z25, the OVM and with the added dual supply circuit 

feature.



The DPST master switch has been working OK for 20 years but will benefit 

from the OVM which I think is essential for protection of the ebus.



But have I shown it in the right place for this protection?



The original plans depend on the master switch to isolate battery from 

alternator from bus . There are no alternator or battery disconnect relays.



I see an advantage in using those relays to limit heavy current wiring in 

the cockpit but I already have the wiring and an amp meter with internal shunt.



Is there another advantage in the use of these relays ?



Thanks for your patience as I am obviously at the bottom of the learning 

curve.


	


    The OVM-14 is a device intended to open a breaker or

    other fast acting fault protection. It can easily handle

    300 amps . . . for milliseconds. Departures in wiring from

    those depicted in the 'Connection should be carefully

    considered so as not to violate the device's limits or

    design goals.



    I'm still mystified as to what's driving your design

    study here. Every architecture depicted in the 'Connection

    offers a minimum of two and sometimes three or four

    power sources for devices you'd like to always have

    running. Certainly you're free to re-invent any

    wheels you wish in the fabrication of your project but

    may I suggest that perhaps we should identify deficiencies

    in architectures that have been field tested in perhaps

    thousands of airplanes and address those deficiencies

    while minimizing the risks for unintended consequences?

    The architecture you've shown is guaranteed to generate

    smoke as a result of an ov trip.



    If we don't exercise due diligence in such an exercise,

    I'd be reluctant accept any suggestion that your

    final design was the product of any "assistance" you

    got from the 'Connection or members of this List.



    I got a nastygram from a builder a couple of years

    ago who suffered a lot of unexpected and unhappy events

    with his system and wrote to hammer me for having

    led him astray. After he finally gave up a sketch

    of his architecture, it was obvious that whatever

    benefit he received from the book was not applied

    to his airplane. I sent his drawing back along with

    a check for $33 and a note requesting that he refrain

    from telling anyone that I had anything to do with

    his project for it was obvious that I did not.



    I wonder sometimes at Greg Richter's claim: "I've

    seen so much truly atrocious work, much of it per Bob's

    book". If someone acquired the book and then set

    fire to their airplane, it's exceedingly doubtful

    that they benefited from ownership of the book. In

    such cases, I'm justified in "disowning" them as

    customers.



    There's a better way to get where you want to

    go with this system my friend but so far we've

    yet to set the train up on the rails that lead

    to success.



    Bob . . .

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Tue May 01, 2007 2:33 pm Post subject: BASIC DUAL POWER SUPPLY

Bob,

I did not mean to strike a raw nerve reflecting on your work and I apologise

if my ideas or questions are received that way. It is not intended, I just

like to know how and why.   

Ken has explained the OVM-trip-relay sensitivity to answer that question

which should help to keep the smoke down to a minimum.

I am working with old architecture and a PM alternator in an attempt to make

a safe dual power source. The rest of what I need to know seems to be

covered in Z16.I am open to any other suggestions.

Thanks

Peter



--

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nuckollsr(at)cox.net
Guest

Posted: Wed May 02, 2007 5:15 am Post subject: BASIC DUAL POWER SUPPLY

At 08:30 AM 5/2/2007 +1000, you wrote:



 	  Quote: 	
		  

<peterjfharris(at)bigpond.com>



Bob,

I did not mean to strike a raw nerve reflecting on your work and I apologise

if my ideas or questions are received that way. It is not intended, I just

like to know how and why.


	


   I didn't intend to come off that way. It was just a hypothetical

   musing as to how a lot of what looks and sniffs like stuff in

   the 'Connection is not work that we can properly . . . nor would

   we claim as members of the society for the filtering and assembly

   of simple ideas (SFASI).



   You have nothing to apologize for. I was simply hashing over

   a point about making changes to a successful recipe without

   making a due-diligence evaluation of what "improvement" is being

   sought and attempting to deduce all the unintended consequences

   for having made changes. My comments were not directed at

   anyone, particularly you sir. It was just a manifestation of some

   degree of frustration with all the $time$ expended on a somewhat

   random stirring of ideas with out benefit of SFASI. I'm seeing a

   LOT of that where I work these days and no doubt most of my

   frustration comes from that source.



   I was chartered to investigate the simple ideas behind

   a situation that has cost us somewhere around a half million

   dollars off the bottom line due to an ill conceived idea going

   to production about 6 years ago. Now that the pressure to "fix"

   it has reached the tipping point, there are others whining about

   the $100,000 it's going to take to correct the problem and still

   others eager to apply their policy-and-procedure driven charters

   to levy piles of senseless paper work onto the task. So the

   cash drain goes on, folks on the line continue to curse the

   engineers and we hat-dance around the paper pile for another

   6 months or so. This ladies and gentlemen smells strongly of

   stupidity . . . for which there is no cure. My time there may

   be more limited than I had originally planned.



   Many folks have interpreted my position as being a severe case

   of "not invented here" syndrome. They don't understand the time

   and thought processes needed to evaluate a variation on one of

   the Z-figures . . . especially when only one feature is being

   discussed out of context as it were.



   This is why I've suggested that we always start with one of

   the Z-figures, compare its capabilities with your mission and

   hardware and consider incremental changes necessary to cover

   some new or overlooked feature. Each of the Z-figures evolved

   out of exactly these kinds of discussions over the past 20

   years. It may be that we'll discover the need for a new Z-figure

   after we discuss your needs in more detail.



 	  Quote: 	
		  Ken has explained the OVM-trip-relay sensitivity to answer that question

which should help to keep the smoke down to a minimum.

I am working with old architecture and a PM alternator in an attempt to make

a safe dual power source. The rest of what I need to know seems to be

covered in Z16.I am open to any other suggestions.


	


   I went to my archives and found 38 posts on this thread over

   the last 20 days or so. I don't have time to sift through them

   all for pertinent points so please indulge my ignorance and

   update me on the pertinent points. As I recall . . .



   Which "old" architecture? I understand you have a Jabiru engine

   with a PM alternator. The 3300? I seem to recall that you were

   having trouble with getting the charging system to work. Is that

   resolved? There were several thread topics . . . one about

   regulator choices and the other about dual power supply. I

   note from the Jabiru manual that they're offering a 3-phase

   alternator but the wiring diagrams still show the 2-phase vesion.

   A schematic of the regulator shows it to be of the same general

   philosophy as the Ducati regulator supplied with Rotax engines

   and the regulator supplied with the B&C SD-8. These are not

   inherently self exciting . . . meaning that the regulator will

   not come alive until a battery is connected. However, once in

   operation, the system should produce power after the battery

   is disconnected. The PM alternators don't "stall" in the same

   sense as wound field automotive alternators. In fact, the

   risk to a PM system is stalling the regulator, not the

   alternator. But given that these regulators come alive at

   exceedingly small battery voltages (less than 1 volt) it's

   unlikely (but not impossible) to stall your system by severe

   transient overload if the battery is not on line. This

   raises questions about what kind of accessory in your proposed

   system is capable of "severe" overload?  I suspect only that

   starter would do this so as long as you don't hit the starter

   button sans battery, I perceive no concerns for keeping the

   alternator up and running once it is started.



   What are you system requirements or design goals not met

   by let us say, Figure Z-16? Do you believe your proposed

   system has features with power reliability requirements

   not met by Z-16? Let's discuss it and see first if there

   IS a problem to be solved and then go after it.



   Bob . . .

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