---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 03/04/20: 5 ---------------------------------------------------------- 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 _____________________________________ Time: 06:37:09 AM PST US Subject: AeroElectric-List: Re: OV protection circuit design From: "user9253" 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 _____________________________________ Time: 06:43:18 AM PST US Subject: AeroElectric-List: Re: Battery discharge during normal cruise From: "user9253" 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 _____________________________________ Time: 06:53:01 AM PST US From: Bob Verwey Subject: Re: AeroElectric-List: 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 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 _____________________________________ Time: 07:27:22 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 08:40:08 AM PST US Subject: Re: AeroElectric-List: Battery discharge during normal cruise From: Charlie England 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. 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