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Analyze This

 
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jluckey(at)pacbell.net
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PostPosted: Sun Feb 02, 2014 3:39 pm    Post subject: Analyze This Reply with quote

Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

TIA
Electrical Systems Design Goals:
1. fault tolerant - able to tolerate failure of any single component and fly for 45 min.
2. easy to operate
3. no avionics brown-out on engine start
4. easy to repair
5. comprised of standard, readily-available components
6. cost effective
Pros:
1. simplified operation - only 2 master switches
2. simplified design - single buss

3. no brown-out on engine start
4. automatic fail-over - no pilot interaction required; avionics won't reset

In the event a battery system suffers a failure, either an open circuit or a ground fault, the faulty
system simply stops providing power to the buss and the remaining good system continues to
provide electricity without interruption.
Cons:
1. buss-isolation power diodes may require heat sinks
2. some energy wasted as heat thru power diodes


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nuckolls.bob(at)aeroelect
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PostPosted: Sun Feb 02, 2014 5:57 pm    Post subject: Analyze This Reply with quote

At 05:38 PM 2/2/2014, you wrote:
Quote:
Listers,

Attached find a schematic (some people call them ladder diagrams) of
a design for the electrical system for my RV-7A. Below is a list of
design goals, pros and cons. Please take a look and provide
engineering feedback.

The alternator's b-lead is two diode-drops
removed from the regulator bus sense lead so
expect the b-lead to run 2-drops higher voltage
than the regulator's set-point. With the battery
tapped in between the two diodes, you'll want to
adjust the regulator for a BATTERY voltage of
14.2V

This will peg the b-lead at 14.2+diodeV and
the bus at 14.2-diodeV.

Current limiters are not generally recommended
or demonstrated as useful in battery feeders.

Bob . . .


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jluckey(at)pacbell.net
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PostPosted: Sun Feb 02, 2014 7:44 pm    Post subject: Analyze This Reply with quote

From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Sunday, February 2, 2014 5:56 PM
Subject: Re: Analyze This


--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

At 05:38 PM 2/2/2014, you wrote:
Quote:
Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

The alternator's b-lead is two diode-drops
� removed from the regulator bus sense lead so
expect the b-lead to run 2-drops higher voltage
than the regulator's set-point. With the battery
tapped in between the two diodes, you'll want to
adjust the regulator for a BATTERY voltage of
14.2V

This will peg the b-lead at 14.2+diodeV and
the bus at 14.2-diodeV.

Roger that

Current limiters are not generally recommended
or demonstrated as useful in battery feeders.

If the prove to be problematic, it is very easy to bypass them

thanks bob
sp; -================



[quote][b]


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user9253



Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

PostPosted: Mon Feb 03, 2014 8:01 am    Post subject: Re: Analyze This Reply with quote

The 60 amp fuse protects battery A from an alternator short circuit, but there is no fuse to protect battery B. Either relocate the 60 amp fuse to the alternator side of the diodes or else add a second 60 amp fuse.
A single shunt could be located in the alternator B lead and eliminate the ammeter selector switch. Or a 3 position selector switch and a third shunt could measure alternator output. Battery current shunts will carry very little current most of the time except after engine start. There have been lots of discussions about the best location for a shunt or if it is actually needed. It is a matter of personal preference.
Joe


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user9253



Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

PostPosted: Mon Feb 03, 2014 10:41 am    Post subject: Re: Analyze This Reply with quote

When the alternator fails, there should be a way to shut off the alternator field to conserve battery energy. Either a pullable circuit breaker or an independent switch.
Joe


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jluckey(at)pacbell.net
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PostPosted: Mon Feb 03, 2014 10:59 am    Post subject: Analyze This Reply with quote

both of those things are on the drawing...

Thx for reviewing,

-Jeff


From: user9253 <fransew(at)gmail.com>
To: aeroelectric-list(at)matronics.com
Sent: Monday, February 3, 2014 10:41 AM
Subject: AeroElectric-List: Re: Analyze This


--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

When the alternator fails, there should be a way to shut off the alternator field to conserve battery energy. Either a pullable circuit breaker or an independent switch.
Joe

--------
Joe Gores


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=418036#418036


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user9253



Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

PostPosted: Mon Feb 03, 2014 4:02 pm    Post subject: Re: Analyze This Reply with quote

Suppose the alternator shorts to ground and the 60 amp fuse blows. Is there a chance that a 100 amp current limiter will also blow?
Joe


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jluckey(at)pacbell.net
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PostPosted: Mon Feb 03, 2014 6:32 pm    Post subject: Analyze This Reply with quote

I would say it's highly unlikely. The 100 amp might warm up but the 60 should hit its melting point before the 100. I don't know how the resistance of a fuse that's in the process of blowing changes. If its resistance goes up, it would begin to limit the current for a few milliseconds until it clears.

-Jeff


From: user9253 <fransew(at)gmail.com>
To: aeroelectric-list(at)matronics.com
Sent: Monday, February 3, 2014 4:02 PM
Subject: Re: Analyze This


--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Suppose the alternator shorts to ground and the 60 amp fuse blows. Is there a chance that a 100 amp current limiter will also blow?
Joe

--------
Joe Gores


Read this topic online here:

http://forums.matronics.com/viewtopisp; -================



[quote][b]


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user9253



Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

PostPosted: Tue Feb 04, 2014 6:31 pm    Post subject: Re: Analyze This Reply with quote

Most aircraft are wired so that starter motor current comes from the battery, through the master contactor, then through the starter contactor to the starter motor. Then if the starter contactor sticks closed, the pilot can break the circuit by shutting off the master switch. I modified Jeff's circuit (attached).
Joe


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PostPosted: Tue Feb 04, 2014 9:02 pm    Post subject: Analyze This Reply with quote

I chose the "non-traditional" approach because:
1. Contactor sticking is exceedingly rare
2. I did not want cranking to be dependent on 2 contactors
3. It allows for more choices when selection a master relay


From: user9253 <fransew(at)gmail.com>
To: aeroelectric-list(at)matronics.com
Sent: Tuesday, February 4, 2014 6:31 PM
Subject: Re: Analyze This


--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Most aircraft are wired so that starter motor current comes from the battery, through the master contactor, then through the starter contactor to the starter motor. Then if the starter contactor sticks closed, the pilot can break the circuit by shutting off the master switch. I modified Jeff's circuit (attached).
Joe

--------
Joe Gores


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=418101#418101


Attachments:

http://forums.matronics.com//files/starter_circuit_194.pdf


sp; - MATRONICS WEB FORUMS -
sp; -->



[quote][b]


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peter(at)sportingaero.com
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PostPosted: Sat Feb 08, 2014 1:09 am    Post subject: Analyze This Reply with quote

Jeff,

I would like a little explanation of the basic operation. I'm assuming both master switches on all the time, both batteries are the same, throw one battery away each year.

If alternator fails no simple load shedding is available, pilot must select items individually (or have a check-list of what to switch off). You're now wasting 2 amps (1 or each battery contactor).

Think about the information you want the 2 shunts to provide, will the do that, is there a better (simpler) way? As you already have the power indicators, I would put the shunt in the alternator to bus feed. Agree with comment about fusing (or current limiting) feed to batt B. I thought a current limiter was better placed in the alternator output?

I'm unsure what the 'K-...' means

2 batteries will provide way more than 45 minutes operation on battery power, even with a very full panel and no load shedding. Therefore system grossly exceeds design goal resulting in more cost/weight than required. Where does 45 minutes come from? FAR-23 requires 30 minutes, alternatively assume half or full fuel endurance.

No simple load shedding appears available - meets goal 2 (but perhaps goal 1 & 2 are actually, survive any failure for 45 minutes with no pilot interaction)

System seems more complex/costly than a 2 bus system would be. Seems that goals 1 & 2 are weighted much more highly than the others?

Its your airplane, build the system that meets your needs.

Regards, Peter


On 02/02/2014 23:38, Jeff Luckey wrote:

[quote] Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

TIA


Electrical Systems Design Goals:
1. fault tolerant - able to tolerate failure of any single component and fly for 45 min.
2. easy to operate
3. no avionics brown-out on engine start
4. easy to repair
5. comprised of standard, readily-available components
6. cost effective


Pros:
1. simplified operation - only 2 master switches
2. simplified design - single buss

3. no brown-out on engine start
4. automatic fail-over - no pilot interaction required; avionics won't reset

In the event a battery system suffers a failure, either an open circuit or a ground fault, the faulty
system simply stops providing power to the buss and the remaining good system continues to
provide electricity without interruption.


Cons:
1. buss-isolation power diodes may require heat sinks
2. some energy wasted as heat thru power diodes







[b]


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jluckey(at)pacbell.net
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PostPosted: Sat Feb 08, 2014 10:52 am    Post subject: Analyze This Reply with quote

Peter,
Thanks for taking the time to review the drawing.� I really appreciate the insightful comments.
My responses are mixed-in with you questions.
Thx again,
-Jeff

From: Peter Pengilly <peter(at)sportingaero.com>
To: aeroelectric-list(at)matronics.com
Sent: Saturday, February 8, 2014 1:08 AM
Subject: Re: AeroElectric-List: Analyze This


Jeff,

I would like a little explanation of the basic operation. I'm assuming both master switches on all the time, both batteries are the same, throw one battery away each year.

Yes - both masters on for normal ops. In addition,
at start-up by turning-on each master individually and
watching the power indicators & volt meter you can
confirm that isolation diodes are functioning properly.
If alternator fails no simple load shedding is available, pilot must select items individually (or have a check-list of what to switch off). You're now wasting 2 amps (1 or each battery contactor).

See comment re load shedding below. My master
relays draw 200 mA each.


Think about the information you want the 2 shunts to provide, will the do that, is there a better (simpler) way? As you already have the power indicators, I would put the shunt in the alternator to bus feed. Agree with comment about fusing (or current limiting) feed to batt B. I thought a current limiter was better placed in the alternator output?

I'm using a zero-center ammeter. With the shunt in
its current location it provides info on the health of
the battery charging system when everything is
working properly.

When the alternator fails, it automatically becomes
a load meter to aid the pilot in load-shedding. Exactly
the info you want, exactly when you need it.

There are fuses in alternator output leads.
An over-voltage protection module will prevent alternator
run-away.

With the shunt in the alternator output, in the case that the
alternator fails, you get no information about system load and
that's when you need it the most in order to do
effective load-shedding.


I'm unsure what the 'K-...' means

'K' is an industry standard abbreviation for relay/contactor


2 batteries will provide way more than 45 minutes operation on battery power, even with a very full panel and no load shedding. Therefore system grossly exceeds design goal resulting in more cost/weight than required. Where does 45 minutes come from? FAR-23 requires 30 minutes, alternatively assume half or full fuel endurance.

That would depend upon battery selection and system load.
I did not provide any info on this for my airplane.
45 minutes is my personal preference.
No simple load shedding appears available - meets goal 2 (but perhaps goal 1 & 2 are actually, survive any failure for 45 minutes with no pilot interaction)
I prefer to be in control of load-shedding based upon the
situation. I don't like the idea of having it predetermined
by what is wired to an E-buss.

If I'm day VFR I may want to turn-off lots of things. If
I'm preparing for an Instrument approach, I may decide
not to turn-off anything.


System seems more complex/costly than a 2 bus system would be. Seems that goals 1 & 2 are weighted much more highly than the others?

Perhaps simplicity/complexity is in the eye of the beholder.
I think a single buss is simpler than multiple busses with
inter-connection/bypass relays.

The buss-isolation diode units cost ~$20 each. I'm willing
to spend the extra $40.


Its your airplane, build the system that meets your needs.

Regards, Peter


On 02/02/2014 23:38, Jeff Luckey wrote:

[quote] Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

TIA


Electrical Systems Design Goals:
1. fault tolerant - able to tolerate failure of any single component and fly for 45 min.
2. easy to operate
3. no avionics brown-out on engine start
4. easy to repair
5. comprised of standard, readily-available components
6. cost effective


Pros:
1. simplified operation - only 2 master switches
2. simplified design - single buss

3. no brown-out on engine start
4. automatic fail-over - no pilot interaction required; avionics won't reset

In the event a battery system suffers a failure, either an open circuit or a ground fault, the faulty
system simply stops providing power to the buss and the remaining good system continues to
provide electricity without interruption.


Cons:
1. buss-isolation power diodes may require heat sinks
2. some energy wasted as heat thru power diodes







[b]


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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:

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peter(at)sportingaero.com
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PostPosted: Mon Feb 10, 2014 1:56 pm    Post subject: Analyze This Reply with quote

Its not me who needs the answers ...

On 08/02/2014 18:50, Jeff Luckey wrote:

[quote] Peter,


Thanks for taking the time to review the drawing. I really appreciate the insightful comments.


My responses are mixed-in with you questions.


Thx again,


-Jeff



From: Peter Pengilly <peter(at)sportingaero.com> (peter(at)sportingaero.com)
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Sent: Saturday, February 8, 2014 1:08 AM
Subject: Re: Analyze This


Jeff,

I would like a little explanation of the basic operation. I'm assuming both master switches on all the time, both batteries are the same, throw one battery away each year.

Yes - both masters on for normal ops. In addition,
at start-up by turning-on each master individually and
watching the power indicators & volt meter you can
confirm that isolation diodes are functioning properly.


If alternator fails no simple load shedding is available, pilot must select items individually (or have a check-list of what to switch off). You're now wasting 2 amps (1 or each battery contactor).

See comment re load shedding below. My master
relays draw 200 mA each.


Think about the information you want the 2 shunts to provide, will the do that, is there a better (simpler) way? As you already have the power indicators, I would put the shunt in the alternator to bus feed. Agree with comment about fusing (or current limiting) feed to batt B. I thought a current limiter was better placed in the alternator output?

I'm using a zero-center ammeter. With the shunt in
its current location it provides info on the health of
the battery charging system when everything is
working properly.

When the alternator fails, it automatically becomes
a load meter to aid the pilot in load-shedding. Exactly
the info you want, exactly when you need it.

There are fuses in alternator output leads.
An over-voltage protection module will prevent alternator
run-away.

With the shunt in the alternator output, in the case that the
alternator fails, you get no information about system load and
that's when you need it the most in order to do
effective load-shedding.


I'm unsure what the 'K-...' means

'K' is an industry standard abbreviation for relay/contactor


2 batteries will provide way more than 45 minutes operation on battery power, even with a very full panel and no load shedding. Therefore system grossly exceeds design goal resulting in more cost/weight than required. Where does 45 minutes come from? FAR-23 requires 30 minutes, alternatively assume half or full fuel endurance.

That would depend upon battery selection and system load.
I did not provide any info on this for my airplane.
45 minutes is my personal preference.


No simple load shedding appears available - meets goal 2 (but perhaps goal 1 & 2 are actually, survive any failure for 45 minutes with no pilot interaction)


I prefer to be in control of load-shedding based upon the
situation. I don't like the idea of having it predetermined
by what is wired to an E-buss.

If I'm day VFR I may want to turn-off lots of things. If
I'm preparing for an Instrument approach, I may decide
not to turn-off anything.


System seems more complex/costly than a 2 bus system would be. Seems that goals 1 & 2 are weighted much more highly than the others?

Perhaps simplicity/complexity is in the eye of the beholder.
I think a single buss is simpler than multiple busses with
inter-connection/bypass relays.

The buss-isolation diode units cost ~$20 each. I'm willing
to spend the extra $40.


Its your airplane, build the system that meets your needs.

Regards, Peter


On 02/02/2014 23:38, Jeff Luckey wrote:

Quote:
Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

TIA


Electrical Systems Design Goals:
1. fault tolerant - able to tolerate failure of any single component and fly for 45 min.
2. easy to operate
3. no avionics brown-out on engine start
4. easy to repair
5. comprised of standard, readily-available components
6. cost effective


Pros:
1. simplified operation - only 2 master switches
2. simplified design - single buss

3. no brown-out on engine start
4. automatic fail-over - no pilot interaction required; avionics won't reset

In the event a battery system suffers a failure, either an open circuit or a ground fault, the faulty
system simply stops providing power to the buss and the remaining good system continues to
provide electricity without interruption.


Cons:
1. buss-isolation power diodes may require heat sinks
2. some energy wasted as heat thru power diodes
















Quote:

[b]


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jluckey(at)pacbell.net
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PostPosted: Tue Feb 11, 2014 5:26 pm    Post subject: Analyze This Reply with quote

Great Peter. If you have any further questions, I'm happy to provide answers...


From: Peter Pengilly <peter(at)sportingaero.com>
To: aeroelectric-list(at)matronics.com
Sent: Monday, February 10, 2014 1:54 PM
Subject: Re: Analyze This


Its not me who needs the answers ...

On 08/02/2014 18:50, Jeff Luckey wrote:

[quote] Peter,


Thanks for taking the time to review the drawing. I really appreciate the insightful comments.


My responses are mixed-in with you questions.


Thx again,


-Jeff



From: Peter Pengilly <peter(at)sportingaero.com> (peter(at)sportingaero.com)
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Sent: Saturday, February 8, 2014 1:08 AM
Subject: Re: Analyze This


Jeff,

I would like a little explanation of the basic operation. I'm assuming both master switches on all the time, both batteries are the same, throw one battery away each year.

Yes - both masters on for normal ops. In addition,
at start-up by turning-on each master individually and
watching the power indicators & volt meter you can
confirm that isolation diodes are functioning properly.


If alternator fails no simple load shedding is available, pilot must select items individually (or have a check-list of what to switch off). You're now wasting 2 amps (1 or each battery contactor).

See comment re load shedding below. My master
relays draw 200 mA each.


Think about the information you want the 2 shunts to provide, will the do that, is there a better (simpler) way? As you already have the power indicators, I would put the shunt in the alternator to bus feed. Agree with comment about fusing (or current limiting) feed to batt B. I thought a current limiter was better placed in the alternator output?

I'm using a zero-center ammeter. With the shunt in
its current location it provides info on the health of
the battery charging system when everything is
working properly.

When the alternator fails, it automatically becomes
a load meter to aid the pilot in load-shedding. Exactly
the info you want, exactly when you need it.

There are fuses in alternator output leads.
An over-voltage protection module will prevent alternator
run-away.

With the shunt in the alternator output, in the case that the
alternator fails, you get no information about system load and
that's when you need it the most in order to do
effective load-shedding.


I'm unsure what the 'K-...' means

'K' is an industry standard abbreviation for relay/contactor


2 batteries will provide way more than 45 minutes operation on battery power, even with a very full panel and no load shedding. Therefore system grossly exceeds design goal resulting in more cost/weight than required. Where does 45 minutes come from? FAR-23 requires 30 minutes, alternatively assume half or full fuel endurance.

That would depend upon battery selection and system load.
I did not provide any info on this for my airplane.
45 minutes is my personal preference.


No simple load shedding appears available - meets goal 2 (but perhaps goal 1 & 2 are actually, survive any failure for 45 minutes with no pilot interaction)


I prefer to be in control of load-shedding based upon the
situation. I don't like the idea of having it predetermined
by what is wired to an E-buss.

If I'm day VFR I may want to turn-off lots of things. If
I'm preparing for an Instrument approach, I may decide
not to turn-off anything.


System seems more complex/costly than a 2 bus system would be. Seems that goals 1 & 2 are weighted much more highly than the others?

Perhaps simplicity/complexity is in the eye of the beholder.
I think a single buss is simpler than multiple busses with
inter-connection/bypass relays.

The buss-isolation diode units cost ~$20 each. I'm willing
to spend the extra $40.


Its your airplane, build the system that meets your needs.

Regards, Peter


On 02/02/2014 23:38, Jeff Luckey wrote:

Quote:
Listers,

Attached find a schematic (some people call them ladder diagrams) of a design for the electrical system for my RV-7A. Below is a list of design goals, pros and cons. Please take a look and provide engineering feedback.

TIA


Electrical Systems Design Goals:
1. fault tolerant - able to tolerate failure of any single component and fly for 45 min.
2. easy to operate
3. no avionics brown-out on engine start
4. easy to repair
5. comprised of standard, readily-available components
6. cost effective


Pros:
1. simplified operation - only 2 master switches
2. simplified design - single buss

3. no brown-out on engine start
4. automatic fail-over - no pilot interaction required; avionics won't reset

In the event a battery system suffers a failure, either an open circuit or a ground fault, the faulty
� system simply stops providing power to the buss and the remaining good system continues to
provide electricity without interruption.


Cons:
1. buss-isolation power diodes may require heat sinks
2. some energy wasted as heat thru power diodes
















Quote:



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