Matronics Email Lists :: View topic - Z8 Ground Power test switch

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Z8 Ground Power test switch
Goto page 1, 2 Next

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Tue Oct 05, 2010 11:30 am Post subject: Z8 Ground Power test switch

In the attached, Ground Power switch is a 3 position (On)-Maintain-On DPDT with indicator lamps. I want to use the (On) switch as a test for power to the GP jack to know when GP is connected to the plane before throwing the switch to the battery.



I was going to just wire the switch from the positive of the GPJ to the (On) through the switch lamp to ground.



Question: If I do that, do I still have OV protection from the 9024 module? It seems that the test circuit is another parallel circuit like the contactor coil circuit and that OVP is preserved.



Thanks,

John

Z8 w-SB ALT-GPJ conceptual .pdf

Description:

Download

Filename:

Z8 w-SB ALT-GPJ conceptual .pdf

Filesize:

439.52 KB

Downloaded:

451 Time(s)

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Wed Oct 06, 2010 7:02 am Post subject: Re: Z8 Ground Power test switch

 	  Quote: 	
		  do I still have OV protection from the 9024 module? 	


No, you do not.  The bottom half of the switch needs to be in series with the circuit breaker, not in parallel.  Also, only one diode is needed.

Joe

_________________
Joe Gores

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Thu Oct 07, 2010 9:47 am Post subject: Re: Z8 Ground Power test switch

Joe,



In the attached, how would you wire the switch so that the contactor coil is not energized when using the momentary half of the switch and yet preserving OV protection for both halves?

GPJ-test switch tentative.pdf

Description:

Download

Filename:

GPJ-test switch tentative.pdf

Filesize:

26.27 KB

Downloaded:

468 Time(s)

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Thu Oct 07, 2010 1:58 pm Post subject: Re: Z8 Ground Power test switch

John,

That is hard to answer without knowing exactly how the switch operates and what you are trying to accomplish.  

If you provide more details about your goals and a data sheet for the switch, then I can confirm or modify my suggestions.

Joe

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Thu Oct 07, 2010 7:09 pm Post subject: Re: Z8 Ground Power test switch

John,

Disregard my previous suggestion.  I deleted my bad advice.  I am going away for a couple of days and will think about your circuit. Meanwhile, explain exactly how you want the circuit to work.

Joe

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Fri Oct 08, 2010 6:29 am Post subject: Re: Z8 Ground Power test switch

John,

How about this circuit?

http://lh4.ggpht.com/_9Rmupq9lpCs/TK8pD8j5DCI/AAAAAAAAAFA/CwjWt8-Vr8o/s640/Gnd%20Pwr001.jpg

Move the switch up between the diode and the contactor coil.  The OV protection will always pop the breaker regardless of switch position.  The switch will enable the contactor coil or the lamp.  The other half of the switch can control the aux alternator as in your original circuit.

Joe

_________________
Joe Gores

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Fri Oct 08, 2010 12:38 pm Post subject: Re: Z8 Ground Power test switch

Joe,



That's great!

I incorporated it in the attached.



I'm still a bit unclear about why the diode is located where it is, but as long as it's correct, I'll read up on that later.



Thanks a bunch,

John

Z8 w-SB ALT-GPJ conceptual rev a .pdf

Description:

Download

Filename:

Z8 w-SB ALT-GPJ conceptual rev a .pdf

Filesize:

510.99 KB

Downloaded:

467 Time(s)

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Fri Oct 08, 2010 12:46 pm Post subject: Re: Z8 Ground Power test switch

Positive Ground Power correction and drawing cleanup

Z8 w-SB ALT-GPJ conceptual rev a .pdf

Description:

Download

Filename:

Z8 w-SB ALT-GPJ conceptual rev a .pdf

Filesize:

464.71 KB

Downloaded:

475 Time(s)

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Fri Oct 08, 2010 3:28 pm Post subject: Z8 Ground Power test switch

Jon;



You're showing a jumper between the starter push button and the starter

warning light. This means that as soon as you engage the starter with the

push button it will latch itself on via this jumper. Probably not  a good

idea.



Bob McC



[quote] --

_________________
Bob McC
Falco #908
(just starting)

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Fri Oct 08, 2010 3:44 pm Post subject: Z8 Ground Power test switch

Jon;



I thought I remembered earlier in this thread that the lamp and diode in

your ground power connector wiring was to warn of reverse polarity?? You

have in the drawings just submitted, however, connected the external power

supply (battery) directly across your auxiliary alternator. Should this be

reversed polarity the alternator will be seen as a direct short and most

probably its internal rectifiers will instantly fry long before the 40 amp

ANL can protect it. To provide reverse polarity protection the external

battery should not be connected to anything aboard the aircraft unless the

polarity is proven to be correct first.

The diode location you're querying causes the lamp to light only if the

ground power is correct polarity and only allows you to close the contactor

if the polarity is correct, but please note the issue above.



Bob McC



[quote] --

_________________
Bob McC
Falco #908
(just starting)

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Fri Oct 08, 2010 9:16 pm Post subject: Re: Z8 Ground Power test switch

Bob,



Thanks for looking this over.



The starter jumper was an errant line that was left over after moving some things around. I removed it and connected the warning lamp circuit to the 'I' terminal of the contactor that receives bus voltage when the contactor is closed.



 	  Quote: 	
		  The diode location you're querying causes the lamp to light only if the

ground power is correct polarity and only allows you to close the contactor

if the polarity is correct, but please note the issue above. 	




So wouldn't that provide the needed protection for the alternator? The way I see it is that, if GP polarity is reversed, it only becomes a problem if the Stby Alt switch is closed. 

I confess that I'm at the ragged end of understanding the circuit and the problems that you foresee. Do you see a solution?



John

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sat Oct 09, 2010 7:02 am Post subject: Z8 Ground Power test switch

Jon;  

   

No.  

   

The problem of frying the alternator isn't caused by closing the contactor, (which rightly won't close via the grnd power switch if the polarity is reversed, or as you suggest via the stby alt switch from the main battery regardless of external battery) it's caused by the fact that the external battery is directly connected across the aux alternator as soon as the plug is inserted into the ground power jack. This is a non-issue with the polarity correct, but it is great cause for concern if the polarity is reversed. This becomes an even greater issue (potentially explosive) should the external power be reversed AND the stby alt switch turned on, because you then have both batteries connected in series and shorted. (24Volts dead short, potentially thousands of amps depending on the type of batteries involved) Providing two separate pathways to activate the contactor raises many of these issues because while you’ve protected one pathway, the other pathway (unprotected) can still activate the circuit.  

   

If you follow the electrical pathways represented by the wires in your latest drawing from your ground power plug, you will find both the plug and alternator grounded of course and thus connected, but you will also find the central pin of the plug connected to the ground power contactor, then via the 40A ANL thru the shunt directly to the alternator. Therefore any external battery is directly connected across the aux alternator regardless of the state of the stby alt switch, grnd power switch, or contactor.   

   

One solution is to connect the 40A ANL to the opposite side of the contactor, but this then raises other issues with being able to isolate the aux alternator when desired etc. and you still have two independent ways to activate the contactor in spite of potential reverse polarity/incorrect voltage etc. The most obvious, simple, safest solution is separate contactors for ground power and the aux alternator, then all of these issues disappear, and the overvoltage/reverse polarity circuit as suggested by Joe works perfectly, but if I remember back far enough this is what this whole exercise was to avoid in the first place.   

   

So, no, sorry, without keeping it simple, I don’t have a satisfactory solution.  

   

As Bob Nuckolls has always advocated, manipulation of any switch, at any time, in any combination or configuration, should never have the potential to create smoke, flames, or any other expensive deleterious consequence, which is why he tries to educate us all to follow the basic simple ideas without adding complexities with their potential associated problems.  

   

Bob McC  

   

> -----Original Message-----  

> From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-  

> server(at)matronics.com] On Behalf Of jonlaury  

> Sent: Saturday, October 09, 2010 1:17 AM  

> To: aeroelectric-list(at)matronics.com  

> Subject: Re: Z8 Ground Power test switch  

>   

> --> AeroElectric-List message posted by: "jonlaury" <jonlaury(at)impulse.net>  

>   

> Bob,  

>   

> Thanks for looking this over.  

>   

> The starter jumper was an errant line that was left over after moving some things  

> around. I removed it and connected the warning lamp circuit to the 'I' terminal of the  

> contactor that receives bus voltage when the contactor is closed.  

>   

>   

> > The diode location you're querying causes the lamp to light only if the  

> > ground power is correct polarity and only allows you to close the contactor  

> > if the polarity is correct, but please note the issue above.  

>   

>   

> So wouldn't that provide the needed protection for the alternator? The way I see it is  

> that, if GP polarity is reversed, it only becomes a problem if the Stby Alt switch is  

> closed.  

> I confess that I'm at the ragged end of understanding the circuit and the problems  

> that you foresee. Do you see a solution?  

>   

> John  

>   

>   

>   

>   

> Read this topic online here:  

>   

> http://forums.matronics.com/viewtopic.php?p=315186#315186  

>   

>   

>   

>   

>   

>   

>   

> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>          - The AeroElectric-List Email Forum -  

  

  

  

  

>  

[b]> style='mso-spacerun:yes'>   --> http://www.matronics.com/Navigator?AeroElectric-List  

>  

[b]> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>               - MATRONICS WEB FORUMS -  

  

>  

[b]> style='mso-spacerun:yes'>   --> http://forums.matronics.com  

>  

[b]> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>             - List Contribution Web Site -  

> style='mso-spacerun:yes'>  Thank you for your generous support!  

> style='mso-spacerun:yes'>                              -Matt Dralle, List Admin.  

> style='mso-spacerun:yes'>   --> http://www.matronics.com/contribution  

> _-  

> ===  

> =======  

>   

>   

   

      [quote][b]

_________________
Bob McC
Falco #908
(just starting)

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sat Oct 09, 2010 7:31 am Post subject: Z8 Ground Power test switch

Jon;



Maybe I've misunderstood your misunderstanding of the reverse polarity

concern. 



When a battery of correct polarity is directly connected to an alternator,

as it is normally in all of our cars and trucks and as it is in the ground

power battery circuit in your electrical drawing, then the rectifier diodes

in the alternator represent an almost infinite resistance to current flow

from the battery to ground through the alternator windings. (an open

circuit) However if the battery is connected in reverse polarity, then the

rectifier diodes represent almost zero resistance to current flow to ground

from the battery through the alternator windings. (A short circuit) This

high current flow supplied by the battery in a "shorted" state will

potentially fry/melt/burn out, the diodes which are not capable of safely

conducting this much current, they are only designed to carry alternator

rated output plus some safety margin. One must remember that a diode is a

one way valve for electricity, conducting in one directing and not in the

other. In normal alternator operation when the voltage generated in the

alternator exceeds the battery voltage sufficiently then current flows from

the alternator into the battery. When the battery voltage exceeds the

voltage generated within the alternator then no current flows.



Reverse the battery polarity and the currents reverse. Alternator represents

a dead short to the battery, not an open circuit as it does with correct

polarity. (The winding resistance does limit current to some extent, but the

battery still sees essentially a short circuit if reversed.)



Does that help??



Bob McC 



[quote] --

_________________
Bob McC
Falco #908
(just starting)

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Sat Oct 09, 2010 8:29 am Post subject: Re: Z8 Ground Power test switch

Bob McC,



 	  Quote: 	
		  Does that help?? 	




Immensely. And I'm extremely appreciative of your efforts to explain the problem in detail to my electrically pedestrian mind. But I need to study my drawing vis a vis your tutorial to fully understand the hazard that you've identified. At some point, Bob N thought that the shared contactor would work and the diode location was jockeyed around for reverse polarity/OV protection and I didn't fully understand then what the issues were. I think I may have complicated the circuit since then, so I need to retrace steps.



  I want to understand this, but adding a contactor may be the most expedient way of getting down the runway.



Thanks,

John

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sat Oct 09, 2010 10:15 am Post subject: Z8 Ground Power test switch

John;   (Is it Jon or John??? Got Jon from your e-mail address. Sorry if I was wrong)  

   

Glad I'm able to shed some light.  

   

There are at least three distinct and separate hazards.   

   

One is the simple reverse polarity battery connected directly to an alternator. No switches or contactors involved, which will likely damage the alternator.  

   

Two is the ability to close the grnd power contactor (via the aux alt switch) with a reversed ground power battery connected, thus creating a short between the two batteries, in spite of the fact that you have reverse power protection preventing closing this same contactor using the ground power switch. One switch thus defeats the protection you have provided for the other.  

   

Three is the possibility of connecting a 24 volt ground power battery to your on board battery, (with unpleasant consequences) through the mechanism described in scenario two above, thus defeating the OV protection built into the ground power switch circuit by energizing the contactor via the unprotected aux alt switch. (Once again that second source defeating the well considered protection provided for the other source)  

   

You cannot take the functional reverse voltage/overvoltage protected circuitry offered by Joe and randomly add devices parallel to portions of it without totally changing how that circuit functions, or at least negating some or all of its features.  

   

Bob N may be correct in that one contactor may suffice, however by introducing multiple switches which mutually defeat the features of each other, you are creating scenarios which leave open the possibility of operator induced failures. The circuitry should take into account that multiple inappropriately positioned switches CANNOT be allowed to create a hazardous situation.  

   

As an aside to what you are trying to accomplish, no switching is required for your ground power present/correct polarity light. If you connect the light to the positive ground power connection as you’ve shown then simply ground the other side through a diode without the switch, then when correct polarity external power is present the lamp will be illuminated and you will know it’s safe to close the contactor. (It will be brighter if a higher than normal voltage is present, but your OV protection will prevent closing the contactor) If you switch on the aux alternator in flight this same light will also now illuminate through virtue of now being connected to the aircraft power buss indicating that aux alternator is energized. If you want to get even more detailed you could add a second light (large red??) parallel to the first connected to the ground power positive pin and grounded through a diode but whose polarity is reversed with respect to the one you’ve already shown. This would illuminate when reverse polarity is present on the ground power jack. Green light = correct polarity ground power present. Red light = reverse polarity ground power present. No lights = no power present.  

   

If you did this you would still need the diode as shown in the circuit switching the contactor in order to provide the reverse polarity protection which prevents you actually connecting the reversed battery.  

   

If you were to eliminate separate ground power and aux alt switches and instead use one three position switch with one position being ground power connected, one being off, and the third being aux alt on, you would make several of these issues go away. (All those caused by having two switches serving the same purpose.) Further if you obtained the ground for this switch from the fuse which you currently show providing ground for your grnd power switch then your OV protection would function with the aux alt as well as with the ground power. This would only leave the issue of a reverse ground power battery connected directly to the alternator to be resolved. That could be addressed by using a two pole contactor whose second set of contacts would be in series with your 40A ANL and whose first contacts would be as presently depicted.  

   

Bob McC  

   

   

> -----Original Message-----  

> From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-  

> server(at)matronics.com] On Behalf Of jonlaury  

> Sent: Saturday, October 09, 2010 12:30 PM  

> To: aeroelectric-list(at)matronics.com  

> Subject: Re: Z8 Ground Power test switch  

>   

> --> AeroElectric-List message posted by: "jonlaury" <jonlaury(at)impulse.net>  

>   

> Bob McC,  

>   

>   

> > Does that help??  

>   

>   

> Immensely. And I'm extremely appreciative of your efforts to explain the problem in  

> detail to my electrically pedestrian mind. But I need to study my drawing vis a vis  

> your tutorial to fully understand the hazard that you've identified. At some point, Bob  

> N thought that the shared contactor would work and the diode location was jockeyed  

> around for reverse polarity/OV protection and I didn't fully understand then what the  

> issues were. I think I may have complicated the circuit since then, so I need to retrace  

> steps.  

>   

>   I want to understand this, but adding a contactor may be the most expedient way of  

> getting down the runway.  

>   

> Thanks,  

> John  

>   

>   

>   

>   

> Read this topic online here:  

>   

> http://forums.matronics.com/viewtopic.php?p=315212#315212  

>   

>   

>   

>   

>   

>   

>   

> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>          - The AeroElectric-List Email Forum -  

  

  

  

  

>  

[b]> style='mso-spacerun:yes'>   --> http://www.matronics.com/Navigator?AeroElectric-List  

>  

[b]> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>               - MATRONICS WEB FORUMS -  

  

>  

[b]> style='mso-spacerun:yes'>   --> http://forums.matronics.com  

>  

[b]> _-  

> ===  

> =======  

> style='mso-spacerun:yes'>             - List Contribution Web Site -  

> style='mso-spacerun:yes'>  Thank you for your generous support!  

> style='mso-spacerun:yes'>                              -Matt Dralle, List Admin.  

> style='mso-spacerun:yes'>   --> http://www.matronics.com/contribution  

> _-  

> ===  

> =======  

>   

>   

   

      [quote][b]

_________________
Bob McC
Falco #908
(just starting)

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Sat Oct 09, 2010 3:44 pm Post subject: Re: Z8 Ground Power test switch

Bob,



 	  Quote: 	
		   (Is it Jon or John?? 	




It's actually John. I've had the email moniker for 20+ years from when ATT would only allow 8 letters. It was for both me and my wife so we shortened my name to 'jon' and Laurie's name to 'laury'. When email  came into common use, my wife got her own address and I stuck with this one.



Once again, you're flooding light on my little dilemma. I like your elegant 3 pos switch (w/appropriate indicator lights) and 2pole contactor idea. Do you know a source for a 2 pole 12vdc 200-300 amp contactor? I didn't pull anything up from Google in a quick search.



The simplest solution is to have stand alone contactors. I can use all my existing switches, wiring,  (FW pass throughs are sealed up), and  the contactor that's mounted for the GPJ. I would just get a  Bosch type 40/60 amp ice cube relay w/neg spike suppression (Beuler makes several), for the stby alternator. I will probably go this route as it is the simplest, smallest and most economical solution. 



Thank you again for trying to keep me from frying myself  .



John

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sat Oct 09, 2010 9:19 pm Post subject: Z8 Ground Power test switch

John;



This manufacturer makes DPST contactors, with many different features and

options available.  http://tinyurl.com/287xe2g   Click on diagrams tab then

click on the JBD series. This is a DPST 200 Amp contactor available in

either continuous or extended duty and with an enclosed option. This is just

one example, there are many others used in the recreational vehicle

industry, by off-roaders for winch control, by the renewable energy industry

for battery control, as well as in golf carts and industrial lift trucks

etc.



However I can't fault your statement below.



Bob McC



 	  Quote: 	
		  The simplest solution is to have stand alone contactors. I can use all my

existing
	


 	  Quote: 	
		   switches, wiring,  (FW pass throughs are sealed up), and  the contactor

that's
	


 	  Quote: 	
		   mounted for the GPJ. I would just get a  Bosch type 40/60 amp ice cube

relay w/neg
	


 	  Quote: 	
		   spike suppression (Beuler makes several), for the stby alternator. I will

probably go
	


 	  Quote: 	
		   this route as it is the simplest, smallest and most economical solution.

 

 Thank you again for trying to keep me from frying myself  .

 

 John

_________________
Bob McC
Falco #908
(just starting)

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Oct 10, 2010 5:05 am Post subject: Z8 Ground Power test switch

Cessna uses a relay at the battery box to prevent reverse polarity form an

incorrectly wired ground source.  If the polarity of the ground plug is

reverse the relay won't close so there is no chance of a reverse polarity

between the aircraft battery and the ground source.  It's a nice simple

system which does however depend on the relay operating and not welding

itself closed.  It would be simple to install a ground power indicator on

the panel so you won't try to take off trailing a ground power supply.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Sun Oct 10, 2010 1:33 pm Post subject: Re: Z8 Ground Power test switch

I agree with Bob McCallum about the danger of reverse polarity with the aux alternator connected in parallel with the ground power.  The two circuits can be isolated with an inexpensive relay like this: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=255-1830-ND or available at auto parts stores.

  Bob N will correct me if I am wrong, but I believe that Z-8 is a work in progress and has not been finalized.  Is the 9024 module available yet?

 Rather than design your own circuit based on Z-8, I suggest that you use one of Bob N's proven circuits like Z-12 or Z-13/8.  Those have an endurance bus, which in my opinion, offer more options and thus safety in case something goes wrong with the electrical system.

  Having a ground power receptacle might make it convenient to get your engine started in case you run the battery down by leaving the master switch on.  But then you will be tempted to take off with an uncharged battery.  And there is the danger of damage to your expensive electronics from reversed polarity or high voltage caused by someone with inexperience or absent mindedness.  Adding more weight and complexity will increase the odds of something going wrong.

 If you are determined to design your own circuit, see the modifications that I made to simplify it and to remove the parallel circuit around the OV circuit breaker.

http://lh3.ggpht.com/_9Rmupq9lpCs/TLItnxSlz0I/AAAAAAAAAFU/_adRmhLnQag/s800/z8_188-a.jpg

Joe

_________________
Joe Gores

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Mon Oct 11, 2010 9:02 am Post subject: Re: Z8 Ground Power test switch

Hi Joe,

Yes, I came to same conclusion about the advantage of separate contactors, after Bob McC pointed out the shortcomings  of my drawn circuitry of using a single contactor for double duty. 



The genesis of this idea was that in an electrically dependent airplane (EDA), one should have a GP jack, rather than having to pull the cowling to get to a battery with jumpers, and  the GP contactor is dead weight for most of it's life. Why not make it pull it's weight by having it be the aux alternator contact as well?



Not as easy as it sounds. And I just got latched on to the idea about saving the weight of a 4th contactor.



For all the weight of the separate ice cube relay, like you showed, I could just leave my pocket change on the hangar bench before flying.



I still would like to see the modified schematic in your post, but it's pretty low resolution as a .jpg file, and gets really fuzzy when I blow it up. Could you post a .pdf of it?



Yes, Z-8 is a work in progress and the 9024 is not available yet. But Bob N was making rumblings that it will be soon. If it's not by the time that I want to fly, I will use a crowbar OV and LVW system on both Alts.

And I did start out using Z-13/8, and then Z-12 but BoB N objected to using the E bus for the loads (20a +) of an EDA and Z-12 puts both alternators on the same bus, eliminating redundancy if the problem is with the bus and it needs to be shut down. It was then that Bob decided that Z-13/20 needed to be revisited for EDA's and came up with Z-8. And I think that by itself, Z-8 is simple and to the point.

Now that I've been brought back to reality with your's and BoB McC's sobering examination and weight/cost/benefit analysis, I am happy with Z-8 and an additional few ounces of contactor for Alt 2.



Thanks for all your help,

John

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours Goto page 1, 2 Next
Page 1 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum