Today's Message Index:
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1. 08:30 AM - Re: Re: Z19 first try and smoke/wire melted I did a mistake (Robert L. Nuckolls, III)
2. 12:35 PM - Re: Re: Z19 first try and smoke/wire melted I did a mistake (Ken Ryan)
3. 01:53 PM - Re: Z19 first try and smoke/wire melted I did a mistake (user9253)
4. 07:47 PM - Re: Re: Z19 first try and smoke/wire melted I did a mistake (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Z19 first try and smoke/wire melted I did |
a mistake
At 08:56 PM 6/16/2018, you wrote:
>
>Thank you bob for you reply. I hope to find just the diode end the
>wire U/S. Many thanks.
>
>I have to check just the integrity of contactor ground wire (master
>switch to the ground bus) easily accessible or I could have other
>wire damaged ?
If the burned wire is in a bundle, there is a
probability for damage to adjacent wires that
should be investigated.
>Because all my wires are set in harness with sleeve.
. . . oh . . . fooey. Not an enviable task.
You might open just a portion of the sleeved
bundle for inspection. Find the contactor control
wire as assess damage to it's insulation and
propagation of damage to other wires.
>About the possible damage, with luck just this wire and diode. But without
>Alternator diode couldn't be damage at least ?
No, it's unlikely that the rest of the
system suffered any damage. To connect the
battery to the system, you have to close the
battery contactor. When battery power is
backwards, the diode across the contactor
coil is essentially a dead short across the
coil. If the diode is small (like a plastic
1N4000 series) it may simply explode and
remove itself from the equation. Not good.
Then the contactor coil closes and reversed
power is applied to the. This still isn't
an automatic condition for total distaster.
The alternator diode array will now become
reverse biased. The array is 6 to 9 diodes
in series pairs that will (1) prevent the
bus voltage from rising to more than a couple
volts . . . for a short period of time. The
b-lead protection device will operate and
disconnect the alternator from the bus.
After this time, all bets are off. But bus
voltage does waayyyy negative to what ever
the battery supplies.
If your contactor diode is mechanically
intact AND the control wire is burned, this
tells us that the contactor never closed.
You'll also find that your b-lead protection
is closed.
>and my ignitions and transpondeur ? (I checked on the user manuel
>they told that inversion of polarity damage it) But in the case of
>switch was in OFF on the transpondeur (for exemple) it can damage it
>? (I ask the question because I was doing a quote of my error to be
>prepared in the event of I have to change part.. and total price
>become quickly crazy)
I think your misery for having suffered this
event will be limited to inspection and repair
of the burned wire and replacement of the
contactor coil suppression diode.
Bob . . .
Message 2
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| Subject: | Re: Z19 first try and smoke/wire melted I did |
a mistake
If the OP had installed a "snapjack" rather than a diode on his battery
contactor, would the contactor have closed, and delivered the reverse
polarity current to the rest of the system? If so, then perhaps this is an
argument in favor of diodes vs snapjacks.
Ken Ryan
On Sun, Jun 17, 2018 at 7:35 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 08:56 PM 6/16/2018, you wrote:
>
>
> Thank you bob for you reply. I hope to find just the diode end the wire
> U/S. Many thanks.
>
> I have to check just the integrity of contactor ground wire (master switch
> to the ground bus) easily accessible or I could have other wire damaged ?
>
>
> If the burned wire is in a bundle, there is a
> probability for damage to adjacent wires that
> should be investigated.
>
> Because all my wires are set in harness with sleeve.
>
>
> . . . oh . . . fooey. Not an enviable task.
> You might open just a portion of the sleeved
> bundle for inspection. Find the contactor control
> wire as assess damage to it's insulation and
> propagation of damage to other wires.
>
>
> About the possible damage, with luck just this wire and diode. But without
> Alternator diode couldn't be damage at least ?
>
>
> No, it's unlikely that the rest of the
> system suffered any damage. To connect the
> battery to the system, you have to close the
> battery contactor. When battery power is
> backwards, the diode across the contactor
> coil is essentially a dead short across the
> coil. If the diode is small (like a plastic
> 1N4000 series) it may simply explode and
> remove itself from the equation. Not good.
> Then the contactor coil closes and reversed
> power is applied to the. This still isn't
> an automatic condition for total distaster.
> The alternator diode array will now become
> reverse biased. The array is 6 to 9 diodes
> in series pairs that will (1) prevent the
> bus voltage from rising to more than a couple
> volts . . . for a short period of time. The
> b-lead protection device will operate and
> disconnect the alternator from the bus.
>
> After this time, all bets are off. But bus
> voltage does waayyyy negative to what ever
> the battery supplies.
>
> If your contactor diode is mechanically
> intact AND the control wire is burned, this
> tells us that the contactor never closed.
> You'll also find that your b-lead protection
> is closed.
>
> and my ignitions and transpondeur ? (I checked on the user manuel they
> told that inversion of polarity damage it) But in the case of switch was in
> OFF on the transpondeur (for exemple) it can damage it ? (I ask the
> question because I was doing a quote of my error to be prepared in the
> event of I have to change part.. and total price become quickly crazy)
>
>
> I think your misery for having suffered this
> event will be limited to inspection and repair
> of the burned wire and replacement of the
> contactor coil suppression diode.
>
>
> Bob . . .
>
Message 3
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| Subject: | Re: Z19 first try and smoke/wire melted I did a mistake |
It does not matter what kind of arc suppression device is in parallel with the
contactor coil. That coil is going to energize when the switch is turned on (unless
the master switch wire burns open). A diode in series with the contactor
coil would prevent it from being energized by a reverse polarity battery.
If a builder were concerned about reverse polarity, two diodes could be used,
one in parallel with the coil and one in series. But what about protection against
line boys with 24 volt jumper cables?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=480956#480956
Message 4
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| Subject: | Re: Z19 first try and smoke/wire melted I did |
a mistake
At 02:33 PM 6/17/2018, you wrote:
>If the OP had installed a "snapjack" rather than a diode on his
>battery contactor, would the contactor have closed, and delivered
>the reverse polarity current to the rest of the system? If so, then
>perhaps this is an argument in favor of diodes vs snapjacks.
>
>Ken Ryan
Correct. A 'snapjack' is a zener/tvs device in series
with a diode . . . sometimes we see two tvs devices
back to back. The breakdown votlage for selected
devices has to be somewhat greater than system
voltage . . . so yes, this story might have
ended differently if something other than the
plain-vanilla diode were installed . . . or the
diode was not mechanically robust.
We generally don't incorporate reverse polarity
protection on battery contactors. Battery cables
are usually difficult or impossible to hook up
backwards. External batteries on jumper cables
is another matter.
I believe I've shown reverse polarity protection
on all the ground power circuits . . . some include
OV protection as well.
Bob . . .
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