Today's Message Index:
----------------------
1. 06:37 AM - Re: OV protection circuit design (user9253)
2. 06:43 AM - Re: Battery discharge during normal cruise (user9253)
3. 06:53 AM - Re: Re: OV protection circuit design (Bob Verwey)
4. 07:27 AM - Re: Battery discharge during normal cruise (Robert L. Nuckolls, III)
5. 08:40 AM - Re: Battery discharge during normal cruise (Charlie England)
Message 1
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| Subject: | Re: OV protection circuit design |
I would not use 12 AWG because it is too big and hard to work with. It
might even damage components that are not designed for large wire.
I would rather use a fuselink, like Charlie said, than use #12 wire.
Electrical circuits require two types of protection, short circuit and
overload. A short circuit occurs when two conductors touch each other.
The current will be very high. An overload occurs when the load draws
more current than it was designed for. Fuses protect against short circuits.
Circuit breakers protect against overloads. Although sometimes only one
type (fuse or breaker) is used to protect a circuit against both types of faults.
In the case of the alternator over-voltage module shorting to ground, we
are dealing with a short circuit. We want the circuit breaker to trip, but not
the fuse to blow. I would have suggested using a 35 or 40 amp fuse if it
would fit into the fuse block, but it won't. Normally we choose the fuse
sized based on the wire size. But in this case, we are not dealing with a
continuous load. We are dealing with a short circuit that only lasts a few
seconds at most. It takes time for a wire to heat up. The circuit breaker
will trip before that happens. Using smaller wire will add resistance to the
circuit, thus helping to limit the maximum current and helping to prevent the
fuse from blowing before the circuit breaker trips. Using 12 AWG wire in this
situation is actually counter productive because the current could be high
enough to both blow the fuse and trip the breaker.
Search the internet for fusing current of wire. It will take over 40 amps
continuous to melt 22 AWG wire. In the time that it takes a 5 amp breaker
to trip, #22 will not even get warm. If 22 AWG wire, between the fuse and
breaker, shorts to ground, the fuse will blow and the wire will not be damaged.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=495144#495144
Message 2
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| Subject: | Re: Battery discharge during normal cruise |
It sounds like a bad connection in the alternator field circuit. Suggest that
you monitor the field voltage right at the alternator.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=495145#495145
Message 3
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| Subject: | Re: OV protection circuit design |
Excellent and succinct, thanks Joe!
Best...
Bob Verwey
082 331 2727
On Wed, 4 Mar 2020 at 16:42, user9253 <fransew@gmail.com> wrote:
>
> I would not use 12 AWG because it is too big and hard to work with. It
> might even damage components that are not designed for large wire.
> I would rather use a fuselink, like Charlie said, than use #12 wire.
> Electrical circuits require two types of protection, short circuit and
> overload. A short circuit occurs when two conductors touch each other.
> The current will be very high. An overload occurs when the load draws
> more current than it was designed for. Fuses protect against short
> circuits.
> Circuit breakers protect against overloads. Although sometimes only one
> type (fuse or breaker) is used to protect a circuit against both types of
> faults.
> In the case of the alternator over-voltage module shorting to ground, we
> are dealing with a short circuit. We want the circuit breaker to trip,
> but not
> the fuse to blow. I would have suggested using a 35 or 40 amp fuse if it
> would fit into the fuse block, but it won't. Normally we choose the fuse
> sized based on the wire size. But in this case, we are not dealing with a
> continuous load. We are dealing with a short circuit that only lasts a
> few
> seconds at most. It takes time for a wire to heat up. The circuit
> breaker
> will trip before that happens. Using smaller wire will add resistance to
> the
> circuit, thus helping to limit the maximum current and helping to prevent
> the
> fuse from blowing before the circuit breaker trips. Using 12 AWG wire in
> this
> situation is actually counter productive because the current could be high
> enough to both blow the fuse and trip the breaker.
> Search the internet for fusing current of wire. It will take over 40
> amps
> continuous to melt 22 AWG wire. In the time that it takes a 5 amp breaker
> to trip, #22 will not even get warm. If 22 AWG wire, between the fuse and
> breaker, shorts to ground, the fuse will blow and the wire will not be
> damaged.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=495144#495144
>
>
Message 4
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| Subject: | Re: Battery discharge during normal cruise |
>What doesn't make sense to me is there are
>periodic and frequent current flows to/from the
>battery (1 to 5 amps) during normal cruise
>operations, this during periods of static and
>relatively light load (12-15 amps) on the
>electrical system, much smaller than the
>capacity of the 60A Plane Power alternator. =C2 =C2
>I would expect all power to be supplied directly
>from the alternator as it is supplying the
>current at a higher voltage (~14.5v or so) than
>the battery.=C2 These periods of flow to/from the
>battery are short in duration normally lasting only a few seconds.
>
>Is this normal and to be expected, or does it
>suggest a problem with the internally regulated
>alternator, or perhaps with the current sensor itself?
It's not 'normal' but it might not be
significant. Current flows into and out
of the battery are manifestations of
and exchange of energy into or out of
the battery.
The battery's physics tells us that significant
energy flows out of the battery at sustained
voltages well below the normal bus voltage . . .
some value below 13 volts.
Since you're not reporting a commensurate
drop in bus voltage associated with these transients,
I am inclined to consider an anomaly in the
data gathering/interpretation/display for
battery current.
Has this always existed with this configuration?
Given the absence of corroborating data I
think I'd just wait and see what happens. In
any case, I don't see a cause for concern.
Bob . . .
Message 5
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| Subject: | Re: Battery discharge during normal cruise |
On 3/4/2020 9:23 AM, Robert L. Nuckolls, III wrote:
>> What doesn't make sense to me is there are periodic and frequent
>> current flows to/from the battery (1 to 5 amps) during normal cruise
>> operations, this during periods of static and relatively light load
>> (12-15 amps) on the electrical system, much smaller than the capacity
>> of the 60A Plane Power alternator. I would expect all power to
>> be supplied directly from the alternator as it is supplying the
>> current at a higher voltage (~14.5v or so) than the battery. These
>> periods of flow to/from the battery are short in duration normally
>> lasting only a few seconds.
>>
>> Is this normal and to be expected, or does it suggest a problem with
>> the internally regulated alternator, or perhaps with the current
>> sensor itself?
>
> It's not 'normal' but it might not be
> significant. Current flows into and out
> of the battery are manifestations of
> and exchange of energy into or out of
> the battery.
>
> The battery's physics tells us that significant
> energy flows out of the battery at sustained
> voltages well below the normal bus voltage . . .
> some value below 13 volts.
>
> Since you're not reporting a commensurate
> drop in bus voltage associated with these transients,
> _*I am inclined to consider an anomaly in the*__*
> *__* data gathering/interpretation/display for*__*
> *__* battery current*_.
>
> Has this always existed with this configuration?
> Given the absence of corroborating data I
> think I'd just wait and see what happens. In
> any case, I don't see a cause for concern.
>
> Bob . . .
>
Bolded segment above reminded me of this:
My Dynon EMS D10 frequently and randomly shows a variable, up to 9A,
discharge (negative current) with stable voltage. I discovered that the
current shunt has a couple of inline fuse holders for glass fuses, and
wiggling the fuse holders will make the negative readings go away.
Obvious takeaway is that excess resistance in the sense lines confuses
the current measurement, quite badly.
Charlie
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