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rvg8tor
Joined: 06 Apr 2009
Posts: 50
Location: Olympia, WA
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 Posted: Tue Oct 27, 2009 10:06 am Post subject: What makes diode get warm |
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I have the B&C diode on the heat sink (smaller one). I was bench testing things to make sure the flow was correct, I just took the breaker panel and hooked up power to the main bus then the E-bus. The diode did not heat up at all, the flow was in the correct direction. I hooked up power to the E-bus and the diode did prevent current to the main bus, the main would only read 0.4 volts which I assume is normal. With this set up the diode again did not heat up. I then hooked up one of the 50W MR16 landing light bulbs to a CB thinking maybe I needed a load, again the diode did not heat up.
So what make the diode heat up, is it more load on the system or is it when there is power going to both buses, as when you have the master on and the E-bus alternate feed on at the same time. With both buses getting power the diode is getting power from both sides. I hear you can fly around this way but not sure I will, my plan now is the have my E-bus alternate feed under a guarded switch that stay off when guarded. When the E-bus gets power from the main via the diode there is a slight voltage drop, the the E-bus alternate feed was on the flow from the battery to the E-bus would win out and supply the E-bus since the voltage from the main is lower. So would this meeting of currents be what heats up the diode? As far as flying around with the E-bus alternate feed on I don't see the need with my system I have a standby alternator. Once I am using standby power then I might consider turning the alternate feed on for automatic switching in case the standby alternator then quit. Thank for the help.
Cheer
Mike
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_________________
Mike "Nemo" Elliott
RV-8A QB (Engine)
www.mykitlog.com/rvg8tor |
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ceengland(at)bellsouth.ne
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| Posted: Tue Oct 27, 2009 11:06 am Post subject: What makes diode get warm |
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rvg8tor wrote:
| Quote: |
I have the B&C diode on the heat sink (smaller one). I was bench testing things to make sure the flow was correct, I just took the breaker panel and hooked up power to the main bus then the E-bus. The diode did not heat up at all, the flow was in the correct direction. I hooked up power to the E-bus and the diode did prevent current to the main bus, the main would only read 0.4 volts which I assume is normal. With this set up the diode again did not heat up. I then hooked up one of the 50W MR16 landing light bulbs to a CB thinking maybe I needed a load, again the diode did not heat up.
So what make the diode heat up, is it more load on the system or is it when there is power going to both buses, as when you have the master on and the E-bus alternate feed on at the same time. With both buses getting power the diode is getting power from both sides. I hear you can fly around this way but not sure I will, my plan now is the have my E-bus alternate feed under a guarded switch that stay off when guarded. When the E-bus gets power from the main via the diode there is a slight voltage drop, the the E-bus alternate feed was on the flow from the battery to the E-bus would win out and supply the E-bus since the voltage from the main is lower. So would this meeting of currents be what heats up the diode? As far as flying around with the E-bus alternate feed on I don't see the need with my system I have a standby alternator. Once I am using standby power then I might consider turning the alternate feed on for automatic switching in case the standby alternator th!
en quit. Thank for the help.
Cheer
Mike
--------
Bob will probably provide a better answer, but the quick & dirty is
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that it's called a 'semi-conductor' because it's not a pure conductor.
There's some resistance even with the electrons flowing 'forward', and
it will heat up due to the work being done pushing them through this
resistance, just like a wire heats up with a lot of current flowing
through it. With more electrons flowing (more current), more heat.
Charlie
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peterlaurence6(at)gmail.c
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| Posted: Tue Oct 27, 2009 12:18 pm Post subject: What makes diode get warm |
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Mike,
If you have a second alternator, and using B&C's regulators, you really
don't need the E buss.
Peter
--
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mprather(at)spro.net
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| Posted: Tue Oct 27, 2009 12:26 pm Post subject: What makes diode get warm |
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| Quote: |
<ceengland(at)bellsouth.net>
rvg8tor wrote:
>
>
> I have the B&C diode on the heat sink (smaller one). I was bench
> testing things to make sure the flow was correct, I just took the
> breaker panel and hooked up power to the main bus then the E-bus. The
> diode did not heat up at all, the flow was in the correct direction. I
> hooked up power to the E-bus and the diode did prevent current to the
> main bus, the main would only read 0.4 volts which I assume is normal.
> With this set up the diode again did not heat up. I then hooked up one
> of the 50W MR16 landing light bulbs to a CB thinking maybe I needed a
> load, again the diode did not heat up.
>
> So what make the diode heat up, is it more load on the system or is it
> when there is power going to both buses, as when you have the master on
> and the E-bus alternate feed on at the same time. With both buses
> getting power the diode is getting power from both sides. I hear you
> can fly around this way but not sure I will, my plan now is the have my
> E-bus alternate feed under a guarded switch that stay off when guarded.
> When the E-bus gets power from the main via the diode there is a slight
> voltage drop, the the E-bus alternate feed was on the flow from the
> battery to the E-bus would win out and supply the E-bus since the
> voltage from the main is lower. So would this meeting of currents be
> what heats up the diode? As far as flying around with the E-bus
> alternate feed on I don't see the need with my system I have a standby
> alternator. Once I am using standby power then I might consider turning
> the alternate feed on for automatic switching in case the standby
> alternator !
th!
> en quit. Thank for the help.
>
> Cheer
> Mike
>
> --------
Bob will probably provide a better answer, but the quick & dirty is
that it's called a 'semi-conductor' because it's not a pure conductor.
There's some resistance even with the electrons flowing 'forward', and
it will heat up due to the work being done pushing them through this
resistance, just like a wire heats up with a lot of current flowing
through it. With more electrons flowing (more current), more heat.
Charlie
Right.
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The ebus diode will run hottest when the ebus is powered through it. To
observe this, the ebus alternate feed switch needs to be open, and power
(battery) directly to the main bus. At this point, any loads on the ebus
will pull current through the diode and cause it to heat up.
Regards,
Matt-
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eschlanser(at)yahoo.com
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| Posted: Wed Oct 28, 2009 8:10 am Post subject: What makes diode get warm |
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| Quote: |
Which Z diagram would it look like without the E buss?
Eric
Time: 01:18:06 PM PST US
From: "plaurence" <peterlaurence6(at)gmail.com (peterlaurence6(at)gmail.com)>
Subject: RE: What makes diode get warm
Mike,
If you have a second alternator, and using B&C's regulators, you really
don't need the E buss.
Peter
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______________________________[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Wed Oct 28, 2009 5:16 pm Post subject: What makes diode get warm |
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At 01:06 PM 10/27/2009, you wrote:
| Quote: |
I have the B&C diode on the heat sink (smaller one). I was bench
testing things to make sure the flow was correct, I just took the
breaker panel and hooked up power to the main bus then the
E-bus. The diode did not heat up at all, the flow was in the
correct direction. I hooked up power to the E-bus and the diode did
prevent current to the main bus, the main would only read 0.4 volts
which I assume is normal. With this set up the diode again did not
heat up. I then hooked up one of the 50W MR16 landing light bulbs
to a CB thinking maybe I needed a load, again the diode did not heat up.
|
Perhaps it did . . . just not enough for you to perceive it
by feeling. Was your e-bus alternate feed switch OPEN
during the test. If so, then the normal feed path diode
would have been carrying all the e-bus loads and it would
warm up.
Why a diode on a heat-sink? How large are your anticipated
e-bus loads? The diode-bridge rectifier mounted on a metal
airframe surface is good for 10+ amps. Schottky diodes
are a bit better yet. I've tested this guy to 20A
http://aeroelectric.com/Catalog/AEC/9001/IM9001-700A.pdf
when mounted on a surface .062" thick with no additional
heat sinking.
| Quote: | So what make the diode heat up, is it more load on the system or is
it when there is power going to both buses, as when you have the
master on and the E-bus alternate feed on at the same time.
|
If the alternate feedpath switch is closed, then the
normal feed-path is bypassed and the diode will carry
no current . . . nor will it warm up.
| Quote: | With both buses getting power the diode is getting power from both
sides. I hear you can fly around this way but not sure I will, my
plan now is the have my E-bus alternate feed under a guarded switch
that stay off when guarded. When the E-bus gets power from the main
via the diode there is a slight voltage drop . . .
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and is the time when it dissipates a few watts of power
and will warm up. The degree of temperature rise depends
on mass and configuration of the heat sink.
| Quote: | . . . the the E-bus alternate feed was on the flow from the
battery to the E-bus would win out and supply the E-bus since the
voltage from the main is lower. . . .
|
The main bus voltage isn't 'lower' but a voltage drop
in the normal feed path becomes insignificant when
the alternate feed path bypasses the diode.
| Quote: | So would this meeting of currents be what heats up the diode? As
far as flying around with the E-bus alternate feed on I don't see
the need with my system I have a standby alternator.
|
How about being able to fire up the comm radio for
ATIS and clearance delivery before starting the engine?
THIS is the time that the alternate feed path
is also tested.
| Quote: | Once I am using standby power then I might consider turning the
alternate feed on for automatic switching in case the standby
alternator then quit. Thank for the help.
|
The purpose of the alternate feed path switch is to
allow battery only operations without having a battery
contactor closed. You didn't mention which, if any
of the Z-figures you based your system. If you're
running Z-12, then having the switch "pre-closed"
offers no degree of automation. I'll suggest you do
a site search on "e-bus" at aeroelectric.com and
review the conversation about how the e-bus came into
being and what it's all about. There's about 30
hits that should offer some insight.
Over the past 15 or so years, folks have tended to
overload the e-bus and/or lost track of the
e-bus design goals. It may well be that your
design goals are served by not having an e-bus.
It's a strong probability that your normal feed-path
diode assembly is oversized.
Bob . . .
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rvg8tor
Joined: 06 Apr 2009
Posts: 50
Location: Olympia, WA
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| Posted: Thu Oct 29, 2009 7:00 am Post subject: Re: What makes diode get warm |
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Bob N.
When I looked at the B&C website for my diode the install instructions for the diode said for an E-bus drawing more than 3 amps to mount the diode on a heat sink, my E-bus will draw 9 amps. So I bought he diode already mounted to the heat sink, I did not think about the fact that just mounting it to the metal panel would provide some heat sink capability.
I have read many posts with regard to E-bus design, my goal was not to fly to my destination if I was battery only but to be able to fly to suitable field, not necessarily the closest field and land to make repairs. In all honesty I think I may never see battery only when I consider the probability of losing both main and standby alternators. I like the insurance of the standby alternator when I consider IFR operations, this is my main reason for adding this to this and hence my adoption of Z-12.
Thanks again for the help you provide it is much appreciated, I have been learning a lot.
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_________________
Mike "Nemo" Elliott
RV-8A QB (Engine)
www.mykitlog.com/rvg8tor |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Oct 29, 2009 2:47 pm Post subject: What makes diode get warm |
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At 10:00 AM 10/29/2009, you wrote:
| Quote: |
Bob N.
When I looked at the B&C website for my diode the install
instructions for the diode said for an E-bus drawing more than 3
amps to mount the diode on a heat sink, my E-bus will draw 9
amps. So I bought he diode already mounted to the heat sink, I did
not think about the fact that just mounting it to the metal panel
would provide some heat sink capability.
I have read many posts with regard to E-bus design, my goal was not
to fly to my destination if I was battery only but to be able to fly
to suitable field, not necessarily the closest field and land to
make repairs. In all honesty I think I may never see battery only
when I consider the probability of losing both main and standby
alternators. I like the insurance of the standby alternator when I
consider IFR operations, this is my main reason for adding this to
this and hence my adoption of Z-12.
Thanks again for the help you provide it is much appreciated, I have
been learning a lot.
|
Then leave the e-bus out. There are thousands of Bonanzas,
and large Piper/Cessna singles wired like Z-12. This pre-supposes
that you're not interested in the pre-flight power up of a
comm radio before starting the engine.
Z-12 Works good, lasts a long time.
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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laracroft
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| Posted: Fri Oct 30, 2009 9:29 pm Post subject: Re: What makes diode get warm |
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Hi,
Me Laracroft,
The diode will heat when the ebus is powered through it. To observe this, the ebus alternate feed switch needs to be open, and power (battery) directly to the main bus. so I am agree with Mike.
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