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Sam
Joined: 18 May 2008
Posts: 135
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 Posted: Fri Aug 14, 2009 8:11 am Post subject: Two fuses in series? |
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Is it ever logical to put two fuses in series? I am attaching a PDF. In the lower center area of the drawing, look at the switch labeled ECU PWR & Injectors.
The idea is, if the SYS A ECU should blow, I wouldn't want a common fuse taking out the SYS B ECU. Or is there another way to do this without adding anymore switches? Maybe a fuse link, back at the main battery bus?
I now have 9 test flights in and I'm still fighting oil temp and highly experimental induction issues.
Thanks.
Sam
www.samhoskins.blogspot.com
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nuckolls.bob(at)aeroelect
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| Posted: Fri Aug 14, 2009 6:31 pm Post subject: Two fuses in series? |
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At 11:01 AM 8/14/2009, you wrote:
| Quote: | Is it ever logical to put two fuses in series? I am attaching a
PDF. In the lower center area of the drawing, look at the switch
labeled ECU PWR & Injectors.
The idea is, if the SYS A ECU should blow, I wouldn't want a common
fuse taking out the SYS B ECU. Or is there another way to do this
without adding anymore switches? Maybe a fuse link, back at the
main battery bus?
I now have 9 test flights in and I'm still fighting oil temp and
highly experimental induction issues.
|
Each ECU should enjoy its own fuse at the bus and
ideally be switched with it's own power switch.
Alternatively, consider going to a 3-pole switch
so that the two ECU's have no power path in common,
only the single switch.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
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Sam
Joined: 18 May 2008
Posts: 135
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| Posted: Fri Aug 14, 2009 7:19 pm Post subject: Two fuses in series? |
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Yes, that is my preference, but I haven't figured out how to do that. The limitation is the number of switches I already have installed, as seen at the top of the drawing, and space limitation. I tried to install B&Cs OFF-ON-ON switch, but it is fatter than the rest and does not fit.
I am dumfluxed. It is not an easy solution. If it was, I would have nailed it down a year ago.
Sam
On Fri, Aug 14, 2009 at 9:30 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
At 11:01 AM 8/14/2009, you wrote:
| Quote: | Is it ever logical to put two fuses in series? I am attaching a PDF. In the lower center area of the drawing, look at the switch labeled ECU PWR & Injectors.
The idea is, if the SYS A ECU should blow, I wouldn't want a common fuse taking out the SYS B ECU. Or is there another way to do this without adding anymore switches? Maybe a fuse link, back at the main battery bus?
I now have 9 test flights in and I'm still fighting oil temp and highly experimental induction issues.
|
Each ECU should enjoy its own fuse at the bus and
ideally be switched with it's own power switch.
Alternatively, consider going to a 3-pole switch
so that the two ECU's have no power path in common,
only the single switch.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
===========
-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
===========
http://forums.matronics.com
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le, List Admin.
="_blank">http://www.matronics.com/contribution
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[b]
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Sam Hoskins
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jay(at)horriblehyde.com
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| Posted: Fri Aug 14, 2009 10:42 pm Post subject: Two fuses in series? |
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Hello Sam,
The principle is not unusual in protection of power electrical systems; isolation of part of a system rather than the whole system. I would be concerned with the actual tripping characteristic of the fuse though. Normally protective devices, such as a fuse, have an ‘inverse time tripping’ characteristic- which means that the higher the current through them the faster they trip/ blow. When one is coordinating the protection on a power electrical system you need to make sure that these characteristics do not overlap so that the ‘upstream’ fuse/device does not trip first. I think that you would need to use what are called ‘fast blow’ fuses for the 5A fuse and ‘slow blow’ for the 10A so that the 10A fuse gives the 5A a chance to clear the fault.
How come you do not have a 5A fuse in the ‘SYS B’ ECU circuit?
Jay
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Sam Hoskins
Sent: 14 August 2009 06:02 PM
To: Aerolectric List
Subject: Two fuses in series?
Is it ever logical to put two fuses in series? I am attaching a PDF. In the lower center area of the drawing, look at the switch labeled ECU PWR & Injectors.
The idea is, if the SYS A ECU should blow, I wouldn't want a common fuse taking out the SYS B ECU. Or is there another way to do this without adding anymore switches? Maybe a fuse link, back at the main battery bus?
I now have 9 test flights in and I'm still fighting oil temp and highly experimental induction issues.
Thanks.
Sam
www.samhoskins.blogspot.com
[quote][b]
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Sam
Joined: 18 May 2008
Posts: 135
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| Posted: Sat Aug 15, 2009 3:43 am Post subject: Two fuses in series? |
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The "A" ECU is the normal running mode and has more features than the "B" side, which is strictly a backup in case of failure of the other. Both ECUs share a single circuit board. The only time the "B" side would normally be used is during engine runup test prior to flight.
The way I have it set up, I am hoping to have the "B" side in reserve. That's why I was wondering about using a fuse link at the main bus.
Sam
On Sat, Aug 15, 2009 at 1:39 AM, Jay Hyde <jay(at)horriblehyde.com (jay(at)horriblehyde.com)> wrote:
[quote]
Hello Sam,
The principle is not unusual in protection of power electrical systems; isolation of part of a system rather than the whole system. I would be concerned with the actual tripping characteristic of the fuse though. Normally protective devices, such as a fuse, have an ‘inverse time tripping’ characteristic- which means that the higher the current through them the faster they trip/ blow. When one is coordinating the protection on a power electrical system you need to make sure that these characteristics do not overlap so that the ‘upstream’ fuse/device does not trip first. I think that you would need to use what are called ‘fast blow’ fuses for the 5A fuse and ‘slow blow’ for the 10A so that the 10A fuse gives the 5A a chance to clear the fault.
How come you do not have a 5A fuse in the ‘SYS B’ ECU circuit?
Jay
From: owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com) [mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)] On Behalf Of Sam Hoskins
Sent: 14 August 2009 06:02 PM
To: Aerolectric List
Subject: AeroElectric-List: Two fuses in series?
Is it ever logical to put two fuses in series? I am attaching a PDF. In the lower center area of the drawing, look at the switch labeled ECU PWR & Injectors.
The idea is, if the SYS A ECU should blow, I wouldn't want a common fuse taking out the SYS B ECU. Or is there another way to do this without adding anymore switches? Maybe a fuse link, back at the main battery bus?
I now have 9 test flights in and I'm still fighting oil temp and highly experimental induction issues.
Thanks.
Sam
www.samhoskins.blogspot.com
| Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
|
[b]
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Sam Hoskins
www.samhoskins.blogspot.com |
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nuckolls.bob(at)aeroelect
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| Posted: Sat Aug 15, 2009 5:19 am Post subject: Two fuses in series? |
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Hello Sam,
The principle is not unusual in protection of power electrical systems; isolation of part of a system rather than the whole system. I would be concerned with the actual tripping characteristic of the fuse though. Normally protective devices, such as a fuse, have an ‘inverse time tripping’ characteristic- which means that the higher the current through them the faster they trip/ blow. When one is coordinating the protection on a power electrical system you need to make sure that these characteristics do not overlap so that the ‘upstream’ fuse/device does not trip first. I think that you would need to use what are called ‘fast blow’ fuses for the 5A fuse and ‘slow blow’ for the 10A so that the 10A fuse gives the 5A a chance to clear the fault.
| Quote: | Correct, in fact it's a
square-law effect where
doubling the current results in about 4x faster trip
time. As a general rule, any upstream fusing is treated
[/b] |
like a feeder protection to another bus and is
MUCH more robust than the largest downstream fuse . . .
This is what ANL style "current limiters' is all
about. In this case, I suspect the individual current
draw for each ECU is low enough that they can be
protected/isolated on 5A (or smaller?) fuses. The
upstream fuse at the bus need not be so robust as
an ANL . . . but 5 to 10x larger than any single
downstream fuse is a good bet.
How come you do not have a 5A fuse in the ‘SYS B’ ECU circuit?
Jay
The "A" ECU is the normal running mode and has more features than the "B" side, which is strictly a backup in case of failure of the other. Both ECUs share a single circuit board. The only time the "B" side would normally be used is during engine runup test prior to flight.
The way I have it set up, I am hoping to have the "B" side in reserve. That's why I was wondering about using a fuse link at the main bus.
Sam
| Quote: | Okay, since you're
"stuck" with the current switch
configuration, let's figure out a work-around. What are
the current demands of each ECU? What I'm thinking about
is coming off the fuse block with a "fat" fuse
like 30A.
Take a 14AWG wire to your switch. Branch off the downstream
side of the switch with a pair of 5A fuses on in-line
fuse-holders, one to each ECU. Do you have a way to
pre-flight
[/b] |
check the integrity of each ECU independently?
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
[quote][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 |
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Sam
Joined: 18 May 2008
Posts: 135
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| Posted: Sat Aug 15, 2009 5:46 am Post subject: Two fuses in series? |
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Yes, I can check independently. I have a douple pole A/B switch which trips the EC3's internal relay. The "at rest" position selects "A". Grounding the circuit causes the relay to operate and selects "B". I am using the other pole of this switch to supply power to the fuel injectors. In the "A" position the main injectors are fed, and in "B" the backup throttle body injector is fed.
The current draw of the ECU less than an amp.
I'll attach the drawing. Thanks!
Sam
On Sat, Aug 15, 2009 at 8:18 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
Hello Sam,
The principle is not unusual in protection of power electrical systems; isolation of part of a system rather than the whole system. I would be concerned with the actual tripping characteristic of the fuse though. Normally protective devices, such as a fuse, have an ‘inverse time tripping’ characteristic- which means that the higher the current through them the faster they trip/ blow. When one is coordinating the protection on a power electrical system you need to make sure that these characteristics do not overlap so that the ‘upstream’ fuse/device does not trip first. I think that you would need to use what are called ‘fast blow’ fuses for the 5A fuse and ‘slow blow’ for the 10A so that the 10A fuse gives the 5A a chance to clear the fault.
| Quote: | Correct, in fact it's a
square-law effect where
doubling the current results in about 4x faster trip
time. As a general rule, any upstream fusing is treated
|
like a feeder protection to another bus and is
MUCH more robust than the largest downstream fuse . . .
This is what ANL style "current limiters' is all
about. In this case, I suspect the individual current
draw for each ECU is low enough that they can be
protected/isolated on 5A (or smaller?) fuses. The
upstream fuse at the bus need not be so robust as
an ANL . . . but 5 to 10x larger than any single
downstream fuse is a good bet.
How come you do not have a 5A fuse in the ‘SYS B’ ECU circuit?
Jay
The "A" ECU is the normal running mode and has more features than the "B" side, which is strictly a backup in case of failure of the other. Both ECUs share a single circuit board. The only time the "B" side would normally be used is during engine runup test prior to flight.
The way I have it set up, I am hoping to have the "B" side in reserve. That's why I was wondering about using a fuse link at the main bus.
Sam
| Quote: | Okay, since you're
"stuck" with the current switch
configuration, let's figure out a work-around. What are
the current demands of each ECU? What I'm thinking about
is coming off the fuse block with a "fat" fuse
like 30A.
Take a 14AWG wire to your switch. Branch off the downstream
side of the switch with a pair of 5A fuses on in-line
fuse-holders, one to each ECU. Do you have a way to
pre-flight
|
check the integrity of each ECU independently?
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
| Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
|
|
| | - 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 |
|
| Description: |
|
Download |
| Filename: |
POWER_DISTRIBUTION0-09-draft01.pdf |
| Filesize: |
80.36 KB |
| Downloaded: |
184 Time(s) |
_________________
Sam Hoskins
www.samhoskins.blogspot.com |
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| Back to top |
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