Strange Coil Troubles
By ghurd, Section Controls Posted on Tue Jun 28, 2005 at 04:25:09 PM MST
One set will just not work

Hi all, I am working on a 20" box fan motor conversion. With 6 coils, wired 3 opposite pairs in series, rectified seperately for testing. Two pairs work just fine. One pair does not. I figured I had one coil backwards in that pair. No problem. Changed it. Still didn't work. Changed it again. Still didn't work. All 6 coils test 9 ohms. Each series pair tests 18 ohms. The 2 that work each make 30V AC open, 1.1A AC shorted, 0.6A DC into a 1.2AH gel battery at 12.6V, maybe ~800RPMs. The one that does not work makes 0.8V AC open. Didn't bother testing any amps. I figure the connections are good, because the ohms are the same as the others. If the ohms are the same, the open voltage should be the same. The 3 pairs of coils are not shorted to each other, or the laminations. I can see how a bad connection can show up with the amps, but not with open volts if the ohms are the same as the coil pairs that do work. I'm more than a little frustrated on this one. Any ideas what I am missing? G-

Strange Coil Troubles | 16 comments (16 topical)

Re: Strange Coil Troubles (3.00 / 0) (#1) by Flux on Tue Jun 28, 2005 at 10:36:15 AM MST

Have you tried measuring the volts on each coil of the pair that don't work? Flux

Re: Strange Coil Troubles (3.00 / 0) (#2) by ghurd on Tue Jun 28, 2005 at 10:40:51 AM MST

I thought of it when I hit the 'post' button. No, I didn't do it yet. Maybe I can do it tommorow.  The computer and shop are 50 miles appart. But it seems like they both would have to be bad to only have 0.8VACopen. Right? Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#3) by Flux on Tue Jun 28, 2005 at 11:30:08 AM MST

I tend to agree, but it has to be the first move.If both have no volts then you have to do a bit of head scratching. Shorted turns in both coils would be unlikely, but you could apply a low ac voltage and measure the current in each coil. Shorted turns don't have much effect on dc resistance but they show up on ac. Difficult to have any other ideas without actually seeing the thing. Let us know what you find. Flux [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#4) by ghurd on Tue Jun 28, 2005 at 11:35:29 AM MST

""Shorted turns... but they show up on ac."" I did not know that! I will add that to the list of things to check. Thanks, G- Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#5) by hiker on Tue Jun 28, 2005 at 02:56:14 PM MST

hook a batt. or batt. charger to the coils in question--then hold a mag in your hand over the coils--is the stringht the same on all three coils--as far as the attraction or repulsion..if theirs a weak one it will have less power [push- pull]..may be shorted windings or shorted to lams..to check to see if its shorted out to lams --just hook up one coil output wire to batt. then touch the other batt. lead to the lams --if theres a short you should see a spark....or just use a ohms meter the same way..   WILD IN ALASKA [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#7) by ghurd on Wed Jun 29, 2005 at 07:54:42 AM MST

I checked all 3 pairs with an ohm meter and got no reading to the lams. Or to other coil pairs. When I check AC amps into the coils at low voltage, I'll check DC amps and field strength also. Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#9) by ghurd on Wed Jun 29, 2005 at 08:16:52 AM MST

Flux, I should have mentioned this is that unusual lay out conversion we talked about a month or 2 ago. With 6 factory coils and 4 magnets. No cogging. No rewind. I'll call it a success even if one pair does not work. Maybe that's why it was in the trash? I think it would be an excelent beginners project for many reasons. I will post pic's and the story when it is finished. Thanks, G- Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#10) by Flux on Wed Jun 29, 2005 at 11:08:01 AM MST

Thanks, I have had a look at the original post. There is absolutely no reason why one pair of coils shouldn't work, the whole thing is symmetrical. If the coils are from the original winding they may be faulty with shorted turns, I assumed that you had wound them recently. If you prove these coils to be faulty and wish to use it with the 2 good pairs, you will do better to remove the dead coils completely, they will absorb power. Flux [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#11) by ghurd on Wed Jun 29, 2005 at 11:29:18 AM MST

Its here, http://www.fieldlines.com/story/2005/5/4/15729/16162 G- Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#16) by ghurd on Sun Jul 03, 2005 at 09:49:36 PM MST

The story and photos are up. "New Idea Makes Box Fan Conversion Very Easy" http://www.fieldlines.com/story/2005/7/4/34446/17324 Thanks a million! G- Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#12) by wooferhound on Wed Jun 29, 2005 at 10:15:52 PM MST

many have tried and failed to make a generator out of a 20" window fan motor. http://www.fieldlines.com/story/2003/12/30/143548/79 W o o f -={( [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#13) by ghurd on Thu Jun 30, 2005 at 03:24:29 AM MST

LOL! I have to call this my biggest success! With 0.6A x 3 = 1.8A into a battery. (thats if the 3rd one works) Also the least expensive. Just adding 4 neos, output wire, 3 bridges, solder, and hot glue. (not sure how good of an idea hot glue is on the coils) No fancy machining either. Could buy ALL the tools I used brand new for $12, including the meter! A little 'outside the box', but kind of an obvious idea after you see a couple pic's. G- Ghurd.info [ Parent ]

Re: Strange Coil Troubles (3.00 / 0) (#6) by wooferhound on Tue Jun 28, 2005 at 03:54:57 PM MST

You pretty much coverd this when you reversed the connections of the 2 coils in the set. But it is likely that you have a coil reversed, mounted with a clockwise twist and not counter-clockwise or visa-versa. W o o f -={(

Re: Strange Coil Troubles (3.00 / 0) (#8) by ghurd on Wed Jun 29, 2005 at 08:04:41 AM MST

Switching them 3 times should have got it right at least once.  I hope! ( But I have done dumber things. Yesterday, changing the wire on that PV that got hit by lightning... Big hurry, starting to storm. Rush, rush, rush. Ran the wire backwards from the controller to the PV.  Cut the wire. Connected the wire to the PV. Solder, anti-corrosion grease, sealed the box... I connected the PV to the dang spool of wire, not the controller wire! LOL! But at least I got it right on the second try! ) G- Ghurd.info [ Parent ]

Bad Coils (3.00 / 0) (#14) by ghurd on Sat Jul 02, 2005 at 09:32:52 PM MST

Thanks Guys. Different RPM from different drill this time. Seperated and tested the pair of non producing coils. One coil tested 18 ohms, double the others. Strange. At 650RPM, 0.8VAC open, 0ma short. The other tested 6 ohms, only 2/3 the others. At 650RPM, 0.02VAC open, 50ma short. The strangest thing is when they were wired in series the ohms were 18. I did not go farther with testing. Those 2 just don't work. :( Maybe there is something bad I did in the planning stages.  It was handled a lot. It was a long time planning involving lots of disassembly and reassembly. I can't believe these 2 coils would be burned or something from life as a fan, because all 6 coils were in series. The chances of only 2 opposite coils being damaged must be slim.  But maybe I just got lucky that 4 do work. I will try to get some pic's, wiring, and numbers up tommorow! G- Ghurd.info

RPM Vs Watts (3.00 / 0) (#15) by ghurd on Sat Jul 02, 2005 at 10:25:32 PM MST

I had the cutin figured before at about 320RPMs. At 650RPMs, only 0.45A into a 12.65V battery.  5.69 watts. At ~800RPMs, 1.2A into a battery before.  15.18 watts. At 1100RPMs, 1.5A into a 12.89V battery.  19.33 watts. (Hey! It did some charging during testing!) Quite a jump from 650RPM to 800RPM, 300% output with a 23% increase in speed. Does that seem normal? G- Ghurd.info [ Parent ]

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