Matronics Email Lists Forum Index Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Redundant Power switching

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List
View previous topic :: View next topic  
Author Message
jonlaury



Joined: 06 Nov 2006
Posts: 336

PostPosted: Mon Jul 19, 2010 11:54 am    Post subject: Redundant Power switching Reply with quote

If I bring separate bus power legs to a DPST to feed a single load, is the current shared (i.e. halved) on the two poles/switches?

- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
View user's profile Send private message
retasker(at)optonline.net
Guest





PostPosted: Mon Jul 19, 2010 5:25 pm    Post subject: Redundant Power switching Reply with quote

Shared, yes. Halved, not likely. How much of the load each pole of the
switch provides depends on the resistance in each leg. Furthermore, if
you are trying to get by with a switch that is not rated per pole for
your total load you will be overloading it. It is very unlikely that
both poles will switch simultaneously so there will be momentary full
loads on one of the poles. Depending on how many times you plan to
operate the switch and what the load is you may have a problem.

If you are doing it with a properly rated switch to provide a redundant
source of power, you have just created a single point of failure - the
switch.

My $0.02.

Dick Tasker

jonlaury wrote:
Quote:


If I bring separate bus power legs to a DPST to feed a single load, is the current shared (i.e. halved) on the two poles/switches?


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=305471#305471



--
Please Note:
No trees were destroyed in the sending of this message. We do concede, however,
that a significant number of electrons may have been temporarily inconvenienced.
--


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
joemotis(at)gmail.com
Guest





PostPosted: Mon Jul 19, 2010 8:14 pm    Post subject: Redundant Power switching Reply with quote

Either leg of the switch has the ampacity of the overcurrent protection device rating available, when either or the sum of both legs reach that value, the overcurrent device will trip.
 
It is still the sum of the total load
that will trip the breaker, not how you divide it downstream of the overcurrent protection.

On Mon, Jul 19, 2010 at 12:54 PM, jonlaury <jonlaury(at)impulse.net (jonlaury(at)impulse.net)> wrote:
[quote]--> AeroElectric-List message posted by: "jonlaury" <jonlaury(at)impulse.net (jonlaury(at)impulse.net)>

If I bring separate bus power legs to a DPST to feed a single load, is the current  shared (i.e. halved) on the two poles/switches?


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=305471#305471
h as List Un/Subscription,
www.matronics.com/Navigator?AeroElectric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
ronics.com/" target="_blank">http://forums.matronics.com
Matt Dralle, List Admin.
=====

[b]


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
jonlaury



Joined: 06 Nov 2006
Posts: 336

PostPosted: Tue Jul 20, 2010 9:59 am    Post subject: Re: Redundant Power switching Reply with quote

Dick and Joe, thanks for your input.

Dick, I will have two switches. The plan is to use the DPST to switch legs of 6-7A and 2A. One switch is a Honeywell AML 34, rated at 125v/15a (at) 60% power factor. The back-up is a Honeywell AML 31, 125v/10a (at) 60% In a similar chart for another switch, Honeywell specifies "Resistive", along with % power factor so I'm assuming that the %power factor is for inductive loads. The 6-7 A load is for electronic fuel injectors which I believe are solenoids and hence, inductive loads.

Joe, I didn't quite follow how the loads on the switch legs are additive. Each pole/switch is separate from the other in the switch and are fed from fuses on separate buses.

J


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
View user's profile Send private message
user9253



Joined: 28 Mar 2008
Posts: 1907
Location: Riley TWP Michigan

PostPosted: Wed Jul 21, 2010 5:31 am    Post subject: Re: Redundant Power switching Reply with quote

Quote:
If I bring separate bus power legs to a DPST to feed a single load, is the current shared (i.e. halved) on the two poles/switches?

The simple answer to your question is, no, not necessarily.
I agree with the other posts above. The problem is that it is not clear exactly how the circuit is wired and what is trying to be accomplished. If you can post an electrical drawing of your circuit, it will be helpful. Do not be too concerned about switch ratings as long as they are in the ballpark. If a switch handles 10 percent more current than its rating, that does not mean that it will be destroyed. Its life will be shortened but that might not matter. Supposing that the life of a switch is rated at 10,000 cycles and due to higher than rated current, it only lasts for 5,000 cycles. It will still last as long as the airplane. Now I am not saying that switch ratings should be ignored. But a switch will not blow up if slightly overloaded. I would use a switch with the proper rating if available.
Joe


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

_________________
Joe Gores
Back to top
View user's profile Send private message
jonlaury



Joined: 06 Nov 2006
Posts: 336

PostPosted: Thu Jul 22, 2010 9:42 am    Post subject: Re: Redundant Power switching Reply with quote

Joe G,

My question was rendered moot by going with two DPST switches, one leg of which powers the EFI ECU and the other, the Injectors, per Dick Tasker's suggestion to eliminate the single point of failure.

I was being kind of myopic wondering if a DPST providing dual power sources to a single load would see 1/2 the load on each leg.

Thanks,
John


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> AeroElectric-List All times are GMT - 8 Hours
Page 1 of 1

 
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


Powered by phpBB © 2001, 2005 phpBB Group