---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 08/29/11: 10 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:01 AM - Maintenace Charger (Mark Richards) 2. 08:37 AM - Re: RV-6A load analysis/architecture (Robert L. Nuckolls, III) 3. 08:46 AM - Re: RV-6A load analysis/architecture (Robert L. Nuckolls, III) 4. 08:53 AM - Re: It's the little things (Robert L. Nuckolls, III) 5. 10:20 AM - Re: Maintenace Charger (Robert L. Nuckolls, III) 6. 01:22 PM - Alternator Wye - what voltage? (Paul Millner) 7. 01:59 PM - Re: Power Supply Connections (William Curtis) 8. 03:20 PM - Re: Re: Power Supply Connections (ROGER & JEAN CURTIS) 9. 04:48 PM - Re: Alternator Wye - what voltage? (Robert L. Nuckolls, III) 10. 09:13 PM - Re: Maintenace Charger (Mark Richards) ________________________________ Message 1 _____________________________________ Time: 08:01:24 AM PST US From: "Mark Richards" Subject: AeroElectric-List: Maintenace Charger Hi Bob; Little off topic but I was wondering if you could give me a specific recommendation for a maintenance charger for my RV batteries. I have 6 U2400's also called US145xc's. These are 6volt deep cycle wet cells rated at 251 amps. At 12 volts this gives about 750amps for the system. Anything out there that you think would work well. Thanks Mark ________________________________ Message 2 _____________________________________ Time: 08:37:35 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: RV-6A load analysis/architecture At 12:03 AM 8/28/2011, you wrote: Vern & Ken, thanks for the input. I figured 10A or so ought to cover charging, but after a cold day start that battery might be pretty taxed. I did forget to consider the lower RPM during taxi and such. Most belt driven alternators on a Lyc are running pretty fast . . . even at idle/taxi speeds. They'll produce a considerable percentage of rated output. Legacy alternator/generator sizing in TC aircraft calls for retaining 25% of rated output for battery charging. There's no particular driver for having recharge take place before takeoff . . . only that the battery be topped off in the first hour to 90 minutes of operation. Alternator: here's where I don't understand the present installation. The present installation has an "Overhauled lightweight 35 Amp alternator" from Mark Landoll's Electrical Service. It includes a Transpo F7078 external regulator. The sales documentation (attached) shows the regulator installed as attached to the alternator. But, the as-built has the regulator installed behind the instrument panel, separated from the alternator. The field line appears to be directly switched. The regulation signal, as stated by the Landoll data sheet as "the wye junction of the Ford stator is the source of the signal for the F7078 regulator. At 1200 RPM, the stator magnitude is only 35 mV." I'm not up to snuff on my motor/generator theory, so I can't visualize what is happening with this setup. This setup doesn't seem to match what I see in the Aeroelectric Connection. Is this an optimal way of doing things, or are there advantages to the ways that Bob describes vs. this Transpo setup? Will the split between alternator and regulator create unforeseen issues? This is a pretty 'old' example of alternator design and implementation. The first alternators we installed on Cessna aircraft had an "S" or stator terminal which was a tap on the center of a 'wye wound' stator. This was used to sense whether or not the engine was running and operate a field disconnect relay. http://aeroelectric.com/Pictures/Regulators/Legacy_EM_Regulator_(Ford).pdf In automobiles, this feature disconnected the alternator field supply when the engine wasn't running thus preventing battery depletion in a parked car. Since airplanes had alternator and battery switches, this feature was not needed. The field relay was controlled directly through the battery/master switch. Later, the solid state ov module was added in series with the relay coil lead http://aeroelectric.com/Pictures/Schematics/Cessna_OVModule.jpg Even if we kept the alternator, I would change the panel mounted B-lead breaker protection to ANL style near the battery. That works. We might up the size of the alternator a bit and go with simple external regulation (generic Ford regulator or such). So, my questions about operation and potential for problems is mostly to satisfy my desire to learn. That would be okay too. The Transpo regulator is probably adequate to the task too but without knowing more details on how it uses/needs the 'stator' connection, I can advise that going to a generic 'Ford' regulator is a sure bed. Second question: We will have a crowbar circuit for OVP, but does anyone see a problem with relying on the GRT EIS4000 to supply the "low voltage" warning? The EIS has a low-RPM maskable low voltage alert. Yes, you want ov protection to be automatic and FAST . . . MILLISECOND fast. Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:46:30 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: RV-6A load analysis/architecture At 12:38 PM 8/28/2011, you wrote: There is nothing fundamentally wrong with any of this. The recommendation to switch the output of the voltage regulator eliminates a lot of problems with switching the input/sense side of some regulators (Bob has a lot of documentation on this problem). The Wye center point is just like the neutral in your house wiring... it should always be close to ground potential except when something bad happens. My guess is the regulator can sense this (similar to a ground fault detector). Not sure what it does when something goes wrong. Not exactly. The 'wye-center-tap' on an alternator will output considerable current . . . at about 1/2 system voltage. It's used for (1) controlling field supply disconnect relays in some designs and/or (2) producing a residual output for getting an alternator to self-excite. This terminal was often labeled "N" on some alternators which led individuals to believe that it was some sort of ground or low-side supply. As for the crowbar... yes! Its very simple and cheap insurance. Dont depend on an audible warning. The OVP protection is much faster. The only issue is keeping the alternator cool when loaded to full capacity at low airspeeds and taxiing. You should be fine if you pay attention to cooling, but theres not a lot of margin. If you can, my suggestion of attaching a temperature probe to the alternator may helpprogram thhe GRT EIS to provide a warning when exceeding about 150C on the diodes so you can do some load shedding. This applies to any rating of alternator. The only alternators that get into cooling trouble in flight are those not properly integrated into the system on day-one. New installations on TC aircraft are tested at max running load during best angle of climb with data corrected for hot- day conditions. This is how some alternators get blast tubes and others do not. Alternator failure due to overheating on an alternator bolted to the front of a Lycoming is very rare and is traceable to some poor choices. If in doubt, do put a thermocouple on the diode heat sink and slip another into the stator winding for exploring the operation during the 40 hr flyoff. But that's a lot of effort that's more likely to be intellectually satisfying than practical. Bob . . . ________________________________ Message 4 _____________________________________ Time: 08:53:34 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: It's the little things My unspoken assumption had been that if the unit received comm, it must have comm power, right? Well, when nothing else pans out, you'll try anything. I whipped out my little voltmeter and tested the comm power pins. 3 volts?? Is that possible? No idea, but when I touched the Main power pins, I got the full 12 volts. I checked out the fuses and voila! My comm power fuse had blown. As I was saying about dopes and electronics... I'm not sure how to explain the 3 volts I did get -- I thought fuses were all-or-nothing affairs, but perhaps not. Anyway, I popped in a new fuse and presto, I get "loud and clear" reports from everybody I talk to. SO.. Maybe the "Comm" power pins need to be relabeled "Transmit" power. And there you have it -- The $100 fuse. The 3-volts you were seeing was probably coming OUT of the radio as opposed to 'sneaking' across an open fuse. Garmin has long been fond of the separate input power for the transmitter of some models. On some models, this input would like to have 28 volts supplied even if the rest of the radio is running on 14 volts. Be sure and check for details on your particular radio. You may want to add a 14/28v up-converter to accommodate the transmitter. It will give you a lot stronger output. http://www.kenneke.com/avionics.html Emacs! Bob . . . ________________________________ Message 5 _____________________________________ Time: 10:20:50 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Maintenace Charger At 09:57 AM 8/29/2011, you wrote: >Hi Bob; > >Little off topic but I was wondering if you could give me a specific >recommendation for a maintenance charger for my RV batteries. I >have 6 U2400's also called US145xc's. These are 6volt deep cycle >wet cells rated at 251 amps. At 12 volts this gives about 750amps >for the system. Anything out there that you think would work well. If you're simply wanting to maintain batteries that are topped off at the time the RV is parked, just about anything would work. But if you want to top-off less-than-full batteries, then something a bit more robust would be called for. Anything with Schumacher's name on it would be a good bet. Here's a 12A, processor controlled charger/ maintainer you can probably pick up at Walmart for $50 or so. Emacs! Bob . . . ________________________________ Message 6 _____________________________________ Time: 01:22:17 PM PST US From: Paul Millner Subject: AeroElectric-List: Alternator Wye - what voltage? >> The Wye center point is just like the neutral in your house wiring... it should always be close to ground potential except when something bad happens. The wye is close to neutral in a three-phase AC generation or motor situation. That's NOT true in our airplanes, where the phases are rectified to DC, since each phase-to-phase pair alternates between being ground on one end and bus voltage on the other end. In that case, the wye floats at about half of bus voltage, but of course is alternating current, not direct. In fact, Bob N's former employer, Beechcraft, took advantage of that on the 12 volt Bonanzas... they attached a six volt *AC* relay between the wye and aircraft ground. When the alternator was putting out power, that relay would close, turning off the "ALTERNATOR FAIL" light. If for whatever reason the alternator quit (open field circuit, broken belt, whatever) then the wye would float near ground, the AC relay would open, and the FAIL light would light. Very clever! I've been tempted to add just such cleverness to my Cessna Cardinal someday... Paul ________________________________ Message 7 _____________________________________ Time: 01:59:13 PM PST US Subject: AeroElectric-List: Re: Power Supply Connections From: William Curtis Below is a link to my home 12 volt electrical system. Hyperlinks are included to all the components. All my various electronics components (cable modem, LAN switch, router, telephones, NAS, 12 volt CFL lights, etc) attach to this system. Additional, I tap into it to charge/run the electrical system on my "still at the house" RV-10. http://wcurtis.nerv10.com/house/dc/12volt.pdf It served me well this past weekend as Irene came through and power was out for about 12 hours. Before shedding load, not including lights, my devices consume about 6 amps. The single Sears U1 battery lasted about 4 hours before I turned on the generator. I put this system in due to frequent power failures (brown-outs and black-outs) in my area. It is cool watching all the WiFi SSIDs in your area go away and yours is the only remaining. I did find out that the power backup on the Internet service provide is only about 6-8 hours however. -- William N40237 - http://wcurtis.nerv10.com/ ________________________________ Message 8 _____________________________________ Time: 03:20:27 PM PST US From: "ROGER & JEAN CURTIS" Subject: RE: AeroElectric-List: Re: Power Supply Connections I tap into it to charge/run the electrical system on my "still at the house" William Do the Feds know you have a still at your house?? You may get a knock at the door as soon as they find out where you live. =98=BA Do not archive ________________________________ Message 9 _____________________________________ Time: 04:48:50 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Alternator Wye - what voltage? At 03:15 PM 8/29/2011, you wrote: >> The Wye center point is just like the neutral in your house wiring... it should always be close to ground potential except when something bad happens. The wye is close to neutral in a three-phase AC generation or motor situation. That's NOT true in our airplanes, where the phases are rectified to DC, since each phase-to-phase pair alternates between being ground on one end and bus voltage on the other end. In that case, the wye floats at about half of bus voltage, but of course is alternating current, not direct. Actually, it is DC albeit half-wave, 3-phase rectified which is pretty 'bumpy'. In fact, Bob N's former employer, Beechcraft, took advantage of that on the 12 volt Bonanzas... they attached a six volt *AC* relay between the wye and aircraft ground. When the alternator was putting out power, that relay would close, turning off the "ALTERNATOR FAIL" light. If for whatever reason the alternator quit (open field circuit, broken belt, whatever) then the wye would float near ground, the AC relay would open, and the FAIL light would light. Very clever! That 'relay' was in fact a little two-transistor, plus jelly-beans dc voltage level sensor. I remember it well. We supplied about 4 versions to Beech and Cessna. During my early years at Electro-Mech, I was cleaning up some drawings and got two capacitors transposed in the bill of materials for the Cessna Wallace Plant version. The thing still passed functional test but behaved badly on the airplanes. Worse yet, the puppies were potted. Needless to say this young fellow was embarrassed to report to the boss that we needed to do a recall on about $30,000 worth of production and launch a quick-turn replacement program. That was more money than I made in a year at that time! Fred would have been fully within 'normal' supervisory parameters to have chewed my you-know-what down to bed-rock. He didn't miss a beat. "Talk to production and get a reading on the replacements . . . I'll have sales notify Cessna and start he recall. Get back to me with a schedule." That's about the only words we had on the matter. I didn't need him to tell me to revise the functional test fixture to offer a more realistic functionality. I always appreciated this man's focus . . . and his class. I've had about five supervisors that I truly revered in my life and Fred Coslett was one of them. I've been tempted to add just such cleverness to my Cessna Cardinal someday... I can probably dig up the schematic of the original but an active LV warning like the AEC9005 is probably closer to the best-we-know-how-to-do today. Better yet, the 9024 program has stumbled back to life. The first 5 or so devices will be offered to individuals who can put them into flying airplanes right now. We'll want to get some field testing of the product and the installation instructions before listing the thing in the catalog. Haven't got a schedule but the software IS moving forward again. Bob . . . ________________________________ Message 10 ____________________________________ Time: 09:13:43 PM PST US From: "Mark Richards" Subject: Re: AeroElectric-List: Maintenace Charger Bob: Thanks for the reommendation. 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