---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 12/13/14: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:32 AM - Re: fuse or breaker for OVP? (user9253) 2. 06:41 AM - Re: fuse or breaker for OVP? (Bob McCallum) 3. 08:16 AM - Re: Overvoltage crowbar availability? (Robert L. Nuckolls, III) 4. 09:27 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III) 5. 09:43 AM - Re: Re: Alternator Disconnect Z17 vs Z20... (Robert L. Nuckolls, III) 6. 09:52 AM - Re: fuse or breaker for OVP? (Ken Ryan) 7. 10:00 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III) 8. 10:03 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:32:51 AM PST US Subject: AeroElectric-List: Re: fuse or breaker for OVP? From: "user9253" Here is a link to the book: http://www.aeroelectric.com/Book/AEC_R12A.pdf -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=435682#435682 ________________________________ Message 2 _____________________________________ Time: 06:41:24 AM PST US From: "Bob McCallum" Subject: RE: AeroElectric-List: fuse or breaker for OVP? Here it is. http://www.aeroelectric.com/Book/AEC_R12A.pdf Bob McC _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jim Kale Sent: Friday, December 12, 2014 11:56 PM Subject: RE: AeroElectric-List: fuse or breaker for OVP? I'd like to down load "the book" if anyone can tell me what it is???? Jim Kale From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Charlie England Sent: Friday, December 12, 2014 5:39 PM Subject: Re: AeroElectric-List: fuse or breaker for OVP? I'm not Jeff, but, A very short length (4"-6") of wire will carry much more current than its 'rated' capacity (which is for much longer lengths), and that's the basis on which the fusible link idea arises. Fusible links are common in cars these days for wire runs that have a very low likelihood of overcurrent due to their load, but still need to be protected from catastrophic faults (like pinched insulation causing a short to ground). You can buy silicone-protected fusible link wire in bulk on line in various sizes for protecting heavier wire. Common practice is to make the link smaller by 4 numbers than the wire it protects (a 16ga link protects a 12ga wire). Like a fuse or breaker, it should be placed on the current source end of the wire. Properly installed, they are much less prone to defect-induced failure than circuit breakers or fuses (and much, much cheaper than a/c circuit breakers). Somewhere in 'the book' you should find a reference to making your own fusible link. It basically amounts to sliding a woven fiberglass sleeve over the smaller gauge wire link and the joint between link & wire. Download the book in digital form & use Acrobat Reader's search function to find the references. If that isn't clear, just ask for more detail. Charlie On 12/12/2014 4:27 PM, Ken Ryan wrote: Thanks Jeff. Your reply is very helpful. I am developing schematics, but have no easy way of scanning them. My system (Rotax) will have two engine driven current producers. One of them is a more traditional alternator with the internal regulator, and the other a permanent magnet affair with an external regulator that the Z diagrams like to refer to as a "Dynamo." I understand how the over voltage protection device is (differently) wired for each of these two current producers, how for the alternator it cuts the field circuit and for the dynamo it disconnects the regulator. But I was unaware that the use of the OVP device eliminates the need for a breaker in the high current charging wire. Now, looking again at the Z drawings, I see that the "fuse" in the high current alternator wire is marked by "note 10" which makes reference to something called a "fuse like device called a current limiter." How is this "current limiter" different from a fuse or breaker and why is it preferable to a fuse or breaker? Now, when I look at the Rotax specific drawing, I see the high current wire from the "dynamo" seems to be protected by a 16 gauge fusible link. The "dynamo" is rated at 22 amps. Is the 16 gauge fusible link up to the task? Why would I want to use a fusible link, rather than a fuse or a breaker? Ken On Fri, Dec 12, 2014 at 12:18 PM, Jeff Luckey wrote: Ken, To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It will just be more difficult to reset ( and it does not give you a convenient way to turn-off the alternator ). However, I'm not sure I'm following you... The best way to shut-down a standard, externally-regulated alternator is to turn-off its regulator. The regulator usually draws less than 1 amp, so you will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the regulator. Like this: Image removed by sender. The Over Voltage Modules we've been talking about are designed to create a short circuit on the field breaker when high voltage is present, thus popping it and shutting-down an errant regulator/alternator. In this scenario, there is no big circuit breaker in the output of the alternator because it's not needed. The output of the alternator is controlled by the regulator & its circuit breaker. (And therein lies the beauty of this system: no big breaker required and no big wires running to that breaker in the panel.) So, I'm a little confused by your question: "... Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown?" Perhaps I'm missing something? Are you referring to one of BobN's Z drawings? Do you have a schematic of the system you are talking about? (a schematic is worth a thousand words) -Jeff On Friday, December 12, 2014 8:23 AM, Ken Ryan wrote: Thanks Jeff. Are you saying that it would be okay to use the OVP device to blow a fuse? Would it be okay to use the bigger breaker in the charging circuit to accomplish a manual shutdown? On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey wrote: The idea behind feeding the Regulator with a circuit breaker is that it gives the pilot the ability to shut-down the alternator (by pulling the breaker) if that becomes necessary. A few reasons you might want to shut down the alternator are: 1. a failed regulator that is giving full field (if you don't have an over voltage module) 2. a failed over-voltage module 3. testing purposes A breaker is simply more practical in this situation. On Thursday, December 11, 2014 3:35 PM, Ken Ryan wrote: I read on another forum that the B&C over voltage protection thingy must only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the chapter on over voltage protection and did not see that mentioned. So the question is, should the OVP device be used to: a) trip a breaker b) blow a fuse c) either is okay ? www.aeroelectric.com http://www.matronics.com/c -Matt Dralle, List - The AeroElectric-List Email List utilities such as List Photoshare, and much much --> http://www.matronics.com/Navigator?AeroElectric-List http://forums.matronics.com==== ________________________________ Message 3 _____________________________________ Time: 08:16:40 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Overvoltage crowbar availability? At 20:43 2014-12-11, you wrote: > >Greetings, > >It looks like B and C no longer carries the stand-alone overvoltage >crowbar (at least I think that's where I bought the one in my LongEz). >I know Bob is trying to get out of the parts distribution business. >Does anyone else know of a source or should I just plan on building >my own. (and if you have the link handy to Bob's schematic that >would be great but don't search if you don't as I'm sure I can find it...). There is a replacement for the legacy crowbar modules in the works. Boards are laid out and software is nearly complete. Probably have some working hardware in the next two weeks. B&C can probably still sell you the older version as well. The new one is software based and much more immune to nuisance trips. It's also packaged to look more like an 'airplane part' than the legacy CBOVM modules. Emacs! Bob . . . ________________________________ Message 4 _____________________________________ Time: 09:27:09 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: fuse or breaker for OVP? At 17:38 2014-12-12, you wrote: >I'm not Jeff, but, > >A very short length (4"-6") of wire will carry >much more current than its 'rated' capacity >(which is for much longer lengths), and that's >the basis on which the fusible link idea arises. >Fusible links are common in cars these days for >wire runs that have a very low likelihood of >overcurrent due to their load, but still need to >be protected from catastrophic faults (like >pinched insulation causing a short to ground). >You can buy silicone-protected fusible link wire >in bulk on line in various sizes for protecting >heavier wire. Common practice is to make the >link smaller by 4 numbers than the wire it >protects (a 16ga link protects a 12ga wire). >Like a fuse or breaker, it should be placed on >the current source end of the wire. Properly >installed, they are much less prone to >defect-induced failure than circuit breakers or >fuses (and much, much cheaper than a/c circuit >breakers). Somewhere in 'the book' you should >find a reference to making your own fusible >link.=C2 It basically amounts to sliding a woven >fiberglass sleeve over the smaller gauge wire >link and the joint between link & wire. Download >the book in digital form & use Acrobat Reader's >search function to find the references. If that >isn't clear, just ask for more detail. It's not described in the book . . . but a search at aeroelectric.com on "fusible link" will produce a comic book on its fabrication . . . Bob . . . ________________________________ Message 5 _____________________________________ Time: 09:43:30 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Alternator Disconnect Z17 vs Z20... Greetings, I'm currently working on wiring up a Quickie with a Rotax 503 (and a glass panel, go figure...). The two architecture diagrams that look appropriate to start from are Z17 "Small Rotax System" (sounds right...) and Z20 "Small Jabiru System". They are basically the same EXCEPT they way the alternator is disconnected (Z17 is downstream of regulator, Z20 is upstream of the regulator). I might be mistaken (please correct me...) but it also appears both diagrams are assuming more of a diode bridge than a real regulator as they both show a 20,000uF cap on the output of the regulator. All z-figures for permanent magnet alternators depict rectifier/regulators as the device of choice for converting the PM alternator's output to DC and then controlling it in a manner friendly to batteries and avionics. Specifications for the 503 state: GENERATOR OUTPUT: 170 W AC at 6000 rpm and 13.5 V RMS RECTIFIER- REGULATOR: (optional) a.) #9103 requires min. load 12 W (1 amp) to regulate b.) #9251 requires no min. load Are you planning to use one of these two rectifier/regulators or some other product? 170 watts of output probably translate to about 14A maximum available output from the r/r . . . do you plan electric start? Have you conducted a load analysis of all planned accessories to determine that you have enough engine driven power to support the load? My questions: 1) What's the significance, if any, of the different approaches to the alternator disconnect? None 2) If I use Rotax 264 870 regulator (as opposed to the 866 080 bridge) is the cap still appropriate (it's not shown in Rotex's wiring diagrams? Where might I find data on these two products? They're not cited as one of the two options in the spec sheet I downloaded. I'm not sure why anyone would ever use an ordinary bridge rectifier between their PM alternator and any other accessory. Can you point me to any literature that describes/recommends this? The capacitor has been a legacy feature of Rotax installations on airplanes for decades. But the little testing I've been able to do on PM alternators and rectifier/regulators cannot confirm the value of adding this device. I'm planing to get another look at the question with more sophisticated equipment in the not too distant future. Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:52:28 AM PST US From: Ken Ryan Subject: Re: AeroElectric-List: fuse or breaker for OVP? On something like a generator charging wire that is connected to the battery, since either end of the wire can be the power source, would it make sense to put a fusible link at each end of the wire? On Sat, Dec 13, 2014 at 8:22 AM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > > At 17:38 2014-12-12, you wrote: > > I'm not Jeff, but, > > A very short length (4"-6") of wire will carry much more current than its > 'rated' capacity (which is for much longer lengths), and that's the basis > on which the fusible link idea arises. > Fusible links are common in cars these days for wire runs that have a ver y > low likelihood of overcurrent due to their load, but still need to be > protected from catastrophic faults (like pinched insulation causing a sho rt > to ground). You can buy silicone-protected fusible link wire in bulk on > line in various sizes for protecting heavier wire. Common practice is to > make the link smaller by 4 numbers than the wire it protects (a 16ga link > protects a 12ga wire). Like a fuse or breaker, it should be placed on the > current source end of the wire. Properly installed, they are much less > prone to defect-induced failure than circuit breakers or fuses (and much, > much cheaper than a/c circuit breakers). Somewhere in 'the book' you shou ld > find a reference to making your own fusible link.=C3=82 It basically amo unts to > sliding a woven fiberglass sleeve over the smaller gauge wire link and th e > joint between link & wire. Download the book in digital form & use Acroba t > Reader's search function to find the references. If that isn't clear, jus t > ask for more detail. > > > It's not described in the book . . . but a search at > aeroelectric.com on "fusible link" will produce a > comic book on its fabrication . . . > > > Bob . . . > > * > =========== m> ldersbooks.com> .com> com> om/contribution> =========== www.matronics.com/Navigator?AeroElectric-List> =========== =========== > > * > > ________________________________ Message 7 _____________________________________ Time: 10:00:49 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: fuse or breaker for OVP? At 17:35 2014-12-11, you wrote: >I read on another forum that the B&C over voltage protection thingy >must only be used to trip a breaker, not to blow a fuse. Yet, I just >re-read the chapter on over voltage protection and did not see that >mentioned. So the question is, should the OVP device be used to: a) >trip a breaker b) blow a fuse c) either is okay ? Either device will function as-intended . . . open the alternator field circuit when an ov condition is detected. Suggest you review the discussions unique to "crowbar" ov protection on aeroelectric.com http://tinyurl.com/q48agpd You will discover both the reasoning behind adoption of this technique along with recommendations for its use on your airplane. If your project includes a circuit breaker panel, then the choice for fuse vs. breakers is moot. If your choice of circuit protection leans toward fuses, then the breaker is recommended for (1) convenient inflight reset (ONLY ONE TIME) in case of a nuisance trip, (2) ground maintenance operations where you'd like to stop a non-rotating alternator from draining the battery. The later is applicable only if you use the simple, two-pole, two-position DC master that brings battery and alternator on at the same time. If you choose to use the three-position, on-on-on switch shown on various z-figures, OFF, BAT, BAT+ALT then the pullable breaker for ground ops is not necessary. But in terms of OV protection, either fuse or breaker will do the job. Bob . . . ________________________________ Message 8 _____________________________________ Time: 10:03:16 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: fuse or breaker for OVP? At 11:47 2014-12-13, you wrote: >On something like a generator charging wire that is connected to the >battery, since either end of the wire can be the power source, would >it make sense to put a fusible link at each end of the wire? Not normally needed. An alternator is magnetically incapable of blowing it's own b-lead protection. You need protect only the battery-end of the b-lead. 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