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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Hi, hoping someone can help.. I have a 3.5 kva electric start portable
petrol generator which has not been used for around 3 years. Motor styarts and runs great, but no generation of any electrical power.. It has been suggested that one should "excite" the armature and another mentions polarizing the armature.....Is there someone out there that can put me on the right track? regards Ray (Victoria,Australia) |
#2
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Motor styarts and runs great, but no generation of any electrical power..
It has been suggested that one should "excite" the armature and another mentions polarizing the armature. Ray- I assume you have checked the wiring and circuit breakers to be sure there is no open circuit. With the motor off, the D.C. resistance measured across the A.C. output terminals should be fairly low. With the motor not running, you might "touch" the AC output circuit with a car battery, or perhaps the battery used for electric start. Hopefully there would be no more than a small spark, but at worst the circuit breaker might pop. I would think that small amount of excitation would accomplish the polarization, and it would take off and deliver power the next time it was started. The next time you start it after attempting the polarization, be sure there is a sizeable load such as an electric heater. Just a light bulb may or may not draw enough current to build up the magnetic field. Fred |
#3
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![]() "ray" wrote in message ... Hi, hoping someone can help.. I have a 3.5 kva electric start portable petrol generator which has not been used for around 3 years. Motor styarts and runs great, but no generation of any electrical power.. It has been suggested that one should "excite" the armature and another mentions polarizing the armature.....Is there someone out there that can put me on the right track? regards Ray (Victoria,Australia) Have you excited it? If it sits long enough you will need to do this before it'll work. |
#4
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Thanks Fred & James,
Your interest & advice is much appreciated. I did get a response from another newsgroup, which advised me to have a look at http://www.endtimesreport.com/dead_gen.html . It turned out to be a comprehensive article entitled "RE-ENERGIZING DEAD GENERATORS " (2.5 pages) In short, it suggests a way of doing it by connecting the output of a spare generator to the output of the dead generator, while the dead generator is being driven by the petrol engine ?? uses three 60 watt globes in series in the connecting line. ?? I am hesitant in trying this procedure, as we are talking about 240 volts AC..... If you could have a look at this article and give me your opinion before I take an action that could turn out to be a really bad thing.... regards Ray |
#5
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If you could have a look at this article and give me your opinion before I
take an action that could turn out to be a really bad thing. Ray- Thanks for posting a link to the generator article. I printed it out, and will add it to my generator folder. The article has a couple of good ideas. If you do as it says, you can probably resuscitate your generator. I would go for using household power, rather than scrounging up a second generator. There were a couple of comments that were not clear to me. He indicated that the three bulbs would start flashing. Actually, flashing is the indication that you have succeeded in polarizing your generator, and is the result of a slight difference in frequency between your generator and the other source of voltage. What he should have said, is that you unplug the connection between the two voltages between flashes, when the bulbs are dark. That is the point when both voltages are identical and in-phase, and zero current is flowing. If you are connecting between the 120 VAC generator outlet and your household 120 VAC outlet, two series-connected 60 watt bulbs would probably be adequate. When the generator is NOT working, the voltage will be about 120 VAC across the bulbs. Then when the generator starts to work, maximum voltage would be 240 VAC across the bulbs, at the point where the two voltages are out of phase. Whatever you do, be VERY CAREFUL. I would probably add a double-pole switch at the plug to be disconnected, to disconnect power "neatly" instead of just pulling a plug that has dangerous voltage on its exposed terminals. Fred |
#6
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When I first read the article I did convinced with the idea of giving
the field excitation with an AC current. It should be DC current to restore the residual megnetism which has lost due to not using for a long time. I googled and found an articles after reading this, that made a little sence. http://www.findarticles.com/p/articl...42/ai_55463575 you should first try with a Battery and then starting the generator with good load. It should work. Excitation with 120V 60 Hz AC with a bulb in series should require only for big industrial generators. Regards, Suraj "ray" wrote in message ... Thanks Fred & James, Your interest & advice is much appreciated. I did get a response from another newsgroup, which advised me to have a look at http://www.endtimesreport.com/dead_gen.html . It turned out to be a comprehensive article entitled "RE-ENERGIZING DEAD GENERATORS " (2.5 pages) In short, it suggests a way of doing it by connecting the output of a spare generator to the output of the dead generator, while the dead generator is being driven by the petrol engine ?? uses three 60 watt globes in series in the connecting line. ?? I am hesitant in trying this procedure, as we are talking about 240 volts AC..... If you could have a look at this article and give me your opinion before I take an action that could turn out to be a really bad thing.... regards Ray |
#7
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![]() "ray" wrote in message ... Thanks Fred & James, Your interest & advice is much appreciated. I did get a response from another newsgroup, which advised me to have a look at http://www.endtimesreport.com/dead_gen.html . It turned out to be a comprehensive article entitled "RE-ENERGIZING DEAD GENERATORS " (2.5 pages) In short, it suggests a way of doing it by connecting the output of a spare generator to the output of the dead generator, while the dead generator is being driven by the petrol engine ?? uses three 60 watt globes in series in the connecting line. ?? I am hesitant in trying this procedure, as we are talking about 240 volts AC..... If you could have a look at this article and give me your opinion before I take an action that could turn out to be a really bad thing.... regards Ray That sounds kinda dangerous! I suggest a safer route, take a 6v lantern battery, or some D batteries in series, a 12v gel-cell, whatever and connect it to the output of the dead generator for a few seconds. |
#9
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That sounds kinda dangerous! I suggest a safer route, take a 6v lantern
battery, or some D batteries in series, a 12v gel-cell, whatever and connect it to the output of the dead generator for a few seconds. Ray & James et al- I agree that the 120 VAC method presents some hazards that would best be avoided. The battery approach would certainly be easy to try, and I think it would work. I think a quick touch should do it. One of the references mentioned a problem if the battery was connected backwards. I believe that was with regard to a DC generator, not an AC generator like the Honda. In this case, I don't think it should make any difference which polarity is used. If someone knows different, please speak up! Fred |
#10
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"Fred McKenzie" bravely wrote to "All" (29 Aug 04 00:00:11)
--- on the heady topic of " re Honda 240/12 v portable generator" FM From: (Fred McKenzie) FM That sounds kinda dangerous! I suggest a safer route, take a 6v FM lantern battery, or some D batteries in series, a 12v gel-cell, FM whatever and connect it to the output of the dead generator for a few FM seconds. FM Ray & James et al- FM I agree that the 120 VAC method presents some hazards that would best FM be avoided. The battery approach would certainly be easy to try, and I FM think it would work. I think a quick touch should do it. FM One of the references mentioned a problem if the battery was connected FM backwards. I believe that was with regard to a DC generator, not an FM AC generator like the Honda. FM In this case, I don't think it should make any difference which FM polarity is used. If someone knows different, please speak up! Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator... A*s*i*m*o*v .... Inductor designers do it in the gap. |
#11
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Fred, how does the iron lose all its magnetism in the first place?
I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator. Asimov- I don't know how, but it apparently happens on rare (?) occasion. Perhaps the earth's magnetic field happens to oppose the residual field due to the orientation of the generator while in storage. I once worked at a place where they made their own permanent magnets used for focusing an electron beam in a traveling wave tube. The field of these magnets was very critical for their application. They were sensitive to shock, as I recall. If one were dropped it would require re-magnetization or recalibration. These magnets were "designed" to retain magnetism by virtue of the choice of the metal alloy. I don't think most alternators or generators use anything special, just iron. One of the references mentioned earlier, suggested that a small permanent magnet was sometimes attached to the iron just for this purpose. I looked at the manual for my Sears/Generac 3500 watt generator. There was no mention of re-polarization, and no permanent magnet was listed in any of the parts lists. It has sat idle for several years at a time, and when restarted has always delivered rated voltage. (I did have to replace the carburetor once!) Fred |
#12
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![]() "Fred McKenzie" wrote in message ... Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator. Asimov- I don't know how, but it apparently happens on rare (?) occasion. Perhaps the earth's magnetic field happens to oppose the residual field due to the orientation of the generator while in storage. I once worked at a place where they made their own permanent magnets used for focusing an electron beam in a traveling wave tube. The field of these magnets was very critical for their application. They were sensitive to shock, as I recall. If one were dropped it would require re-magnetization or recalibration. The earths field is stronger than most imagine from everyday experience. One can induce a weak magnetic field in a piece of soft iron (like rebar) simply by orienting it north and south on it's long axis, and striking with a hammer along that same axis. Afterward, the formerly unmagnitized bar will have enough magnetism to pick up staples, iron filings and the like. Maybe that's the solution for the OP: simply whack it (really hard) with a hammer! Works for a lot of other things.... ;-) jak These magnets were "designed" to retain magnetism by virtue of the choice of the metal alloy. I don't think most alternators or generators use anything special, just iron. One of the references mentioned earlier, suggested that a small permanent magnet was sometimes attached to the iron just for this purpose. I looked at the manual for my Sears/Generac 3500 watt generator. There was no mention of re-polarization, and no permanent magnet was listed in any of the parts lists. It has sat idle for several years at a time, and when restarted has always delivered rated voltage. (I did have to replace the carburetor once!) Fred |
#13
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![]() "jakdedert" wrote in message . .. "Fred McKenzie" wrote in message ... Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator. Asimov- I don't know how, but it apparently happens on rare (?) occasion. Perhaps the earth's magnetic field happens to oppose the residual field due to the orientation of the generator while in storage. I once worked at a place where they made their own permanent magnets used for focusing an electron beam in a traveling wave tube. The field of these magnets was very critical for their application. They were sensitive to shock, as I recall. If one were dropped it would require re-magnetization or recalibration. The earths field is stronger than most imagine from everyday experience. One can induce a weak magnetic field in a piece of soft iron (like rebar) simply by orienting it north and south on it's long axis, and striking with a hammer along that same axis. Afterward, the formerly unmagnitized bar will have enough magnetism to pick up staples, iron filings and the like. Maybe that's the solution for the OP: simply whack it (really hard) with a hammer! Works for a lot of other things.... ;-) jak These magnets were "designed" to retain magnetism by virtue of the choice of the metal alloy. I don't think most alternators or generators use anything special, just iron. One of the references mentioned earlier, suggested that a small permanent magnet was sometimes attached to the iron just for this purpose. I looked at the manual for my Sears/Generac 3500 watt generator. There was no mention of re-polarization, and no permanent magnet was listed in any of the parts lists. It has sat idle for several years at a time, and when restarted has always delivered rated voltage. (I did have to replace the carburetor once!) Fred My Sears generator has a power suppply transformer attached. The only reason for this was excitation of the fields from an alt (permanent magnet in generator) |
#14
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On Sunday, 29 Aug 2004 00:20:10 -500 "Asimov"
wrote: Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator... You're right that there's little reason for residual magnetism to go away. An automotive generator can sit for years or decades and still be fine. That's just for DC generators, however. I don't think there are any AC generators of any significant power that use residual magnetism to bootstrap themselves. They all require a bit of current from some source to get themselves started. The one exception might be brushless AC generators, which I thought were rare. They could be designed to use residual magnetism to get going. Does this AC generator have any brushes? - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
#15
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![]() "Jim Adney" wrote in message ... On Sunday, 29 Aug 2004 00:20:10 -500 "Asimov" wrote: Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator... You're right that there's little reason for residual magnetism to go away. An automotive generator can sit for years or decades and still be fine. That's just for DC generators, however. I don't think there are any AC generators of any significant power that use residual magnetism to bootstrap themselves. They all require a bit of current from some source to get themselves started. The one exception might be brushless AC generators, which I thought were rare. They could be designed to use residual magnetism to get going. Does this AC generator have any brushes? - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- Yes Jim, the generator does have brushes regards Ray |
#16
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![]() "Jim Adney" wrote in message ... On Sunday, 29 Aug 2004 00:20:10 -500 "Asimov" wrote: Fred, how does the iron lose all its magnetism in the first place? I thought that by design there was always supposed to be enough residual magnetism to bootstrap the generator... You're right that there's little reason for residual magnetism to go away. An automotive generator can sit for years or decades and still be fine. That's just for DC generators, however. I don't think there are any AC generators of any significant power that use residual magnetism to bootstrap themselves. They all require a bit of current from some source to get themselves started. The one exception might be brushless AC generators, which I thought were rare. They could be designed to use residual magnetism to get going. Does this AC generator have any brushes? Quite a few portable generators excite themselves from residual magnetism, and yes they have brushes on slip rings. |
#17
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On Tue, 31 Aug 2004 02:14:48 GMT "James Sweet"
wrote: Quite a few portable generators excite themselves from residual magnetism, and yes they have brushes on slip rings. I'm always glad to learn something new, but then I have to wonder why automotive AC generators (alternators) don't do this. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
#18
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![]() "Jim Adney" wrote in message ... On Tue, 31 Aug 2004 02:14:48 GMT "James Sweet" wrote: Quite a few portable generators excite themselves from residual magnetism, and yes they have brushes on slip rings. I'm always glad to learn something new, but then I have to wonder why automotive AC generators (alternators) don't do this. Because they have a battery to do it for them. The field coil is powered through the voltage regulator which recieves power from the battery when the ignition is on. |
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