motor conversion
By christopher, Section Homebrewed Electricity Posted on Sat Dec 11, 2004 at 10:55:32 PM MST
ceramic versus neos

Hi all! Just got my net back up after two hurricanes. Lost my net end of August!!! One hurricane end of August and twenty eight days later another.  It would have been great to find a way to store that power. Near the end of July, I was doing my first motor conversion with very poor output results. Thanks to Flux and Ungrounded Lightning Rod for helping me sort out the problems, suggesting that the ceramic mags I was using were probably not strong enough and to try using neos.  I ordered some from this sight and have recently installed them.  Here are some of the test results: My original test in July was done at 850 rpm with a hand drill, but this was damaged in storm.  New test results are done at 400 rpm with old mags and then redone at the same rpm with the new mags.                                  400 r.p.m.                                       ceramic mags                new neos individual coils open volts           6.70 v.a.c.                 13.40 v.a.c. star open volts                      11.20 v.a.c.                 21.30 v.a.c. D.C. open volts                      15.10 v.d.c.                 27.25 v.d.c. 1 amp bulb load                       7.30 v.d.c.                 14.75 v.d.c.                                 1,000 r.p.m. 12 volt battery load                                              14.80 v.d.c.                                                                   @ 8 amps I started working backwards carving my blades first.  These are three blades, 10' diameter with a TSR of 7.  I was planning to chain drive this at a 1:1 ratio, but now do not think this will give me high enough r.p.m's.  Anyone with any gearing ratio that may help would be most appreciated. Thanks again for all the support.

motor conversion | 11 comments (11 topical)

Re: motor conversion (3.00 / 0) (#1) by hiker on Sat Dec 11, 2004 at 04:24:02 PM MST

well if your good at tearin apart bikes--heres a quick fix...... WILD IN ALASKA

Re: motor conversion (3.00 / 0) (#2) by Jerry on Sat Dec 11, 2004 at 10:14:45 PM MST

Hi Christopher. What are the specs on the motor you've converted? Hp, rpm, volts, amps and single or 3 phase? What NEO magnets did you uses? What gap did you end up with? Could be I've converted a simular motor and may have some blade sugjestions? May then also have some wind test results that could be close or simular?                         JK TAS Jerry Airheads Page

Re: motor conversion (3.00 / 0) (#3) by johnlm on Sat Dec 11, 2004 at 11:09:27 PM MST

Christopher,  A few comments.  By looking at the numbers for the Neo version of your motor conversion I would think a 10 ft dia prop is a bit bigger than necessary.  Also the voltage drop from DC open Voltage to 1A bulb load Voltage looks a bit more drop in Voltage for a 1 A load than one would expect if indeed you are getting 14.8V at 8 Amps at 1000 RPM. Even knocking of a couple of volts for the first bit of loading (which seems to happen) and assuming your drop was really 10.5V from open to 1A of load (on the NEO config), it gives you about a 10.5 Ohm dynamic impedance on your alternator which should result in around 4.5A at 14.8 V on the battery at 1000 RPM.  Whatever. To answer your question- if you are really going to use a 10 ft prop you will have more than enough power to drive the alternator so you may as well try to get to a cutin charging voltage at a fairly low wind speed - say 5mph.  A 10 ft 7 TSR prop will run about 100 RPM at 5 mph and it looks like your alt will hit around 13.6V at 200 RPM so a 2:1 gear up ratio would accomplish that.  And since your alt will not ever be a significant load to a good 10ft prop, you might even be able to start charging at 4 mph and a gear ratio of 2.6 : 1  You already know your alt will put out 14.8V at 8A (118 Watts) at 1000 RPM and the 2.6:1 ratio would have the 10 ft prop running at 385 RPM in this setup which would happen at around 19.5 MPH wind speed at which time your prop would be producing at least 1000 Watts of mechanical power.  That is why I say the 10 ft 7 TSR prop is too big. A 6 ft dia TSR 8 prop, direct drive would probably match this alternator better.  Alot smaller and less stress on things with a 6 footer than a 10 footer that is overkill for your alternator. Is this the type of info you were looking for? Johnlm

Re: motor conversion (3.00 / 0) (#4) by Flux on Sun Dec 12, 2004 at 03:35:17 AM MST

I agree, it looks as though this is a small motor with lots of resistance. It would need gearing about 3:1 for a 10 ft prop and you will need to furl at quite a low wind speed to keep control of it. I agree with John that it would be a better match with direct drive at 6ft if the shaft is big enough to stand it, or gear 2:1 at 8ft if the shaft is not. If you can do the gearing easily give it a try with the 10ft it will make good use of light winds. If you are in a very windy area I think it would be better to use a smaller prop. I would be tempted to use it with a smaller prop and build another alternator that justifies your big prop later. Flux [ Parent ]

Re: motor conversion (3.00 / 0) (#5) by christopher on Sun Dec 12, 2004 at 05:55:42 AM MST

Thanks all for answering all of my questions and more. Thanks for the pic Hiker. Bicycle parts already scrounged and mounted on blade shaft and was waiting to see what gear ratio for alternator sprocket. Flux, this is the Dayton Capacitor A.C. motor conversion you helped me with in July, (3,450 r.p.m., F.L. amps 9.6, Volts 115/208-280).  It is an old bench polisher shaft out both ends 5/8", good bearings.  Rewound with 55 winds of the original wire, 3 phase 8 pole.  If you remember, I had a slight mismatch between phases, two the same, one lower.  I think this was due to reusing the original wire and may have shorted between several winds.  The mags are not a perfect fit,(16 - 1/2 X 1'X 1/4" put N.N. - S.S.), they fill the armiture without any spacing, so overlap the coil legs.  This is probably two reasons why the big voltage drop under load. Thanks Johlm for these Gear ratios.  Why I originally wanted to chain drive was because I did not trust the motor bearings to hold up with the thrust and load of a 10' prop.  I used a car front wheel strut for the blade, mounting them to the brake rotor with the large sprocket attached to the back of this.  My wind speeds are very low 10-12 m.p.h., this was my reasoning for the large prop originally. I am doing another conversion that I hope will be better but for now will try the 10' and let it furl at about 20 m.p.h.  Thanks for all the figures, my math is the pits.     Christopher [ Parent ]

Re: motor conversion (3.00 / 0) (#6) by Flux on Sun Dec 12, 2004 at 06:36:29 AM MST

Yes if it was a high speed motor it will have a small rotor diameter and no space between poles will also waste flux by leakage and will not match the coils properly so it is probably about all you can get. With the low wind area it should be fine with the big prop. Better that way  than big alternator and small prop, that never works out well. The front wheel hub should be good and strong for the big prop. Good luck Flux [ Parent ]

Re: motor conversion (3.00 / 0) (#7) by Jerry on Sun Dec 12, 2004 at 08:41:03 PM MST

Hi Christopher. I agree with the above concenses. I looked back in my wind test book to see the results I got with a simular motor. The 3450 rpm motor is a 2 pole. If you leave the wireing stock it becomes a 2 phase 2 pole. I used 6 of the curved NEOs in mine. NNN, SSS. At 30 mph the genny was producing 450 watts with a direct mounted 49 inch tip to tip 4 blade. I perelelled the 2 run windings then fed a fullwave bridge rectifier. I did the same with the start windings then perelelled the dc outputs of the bridges. No rewireing was nessasary. At least for the 4ft prop and 30 mph winds and 450 watts.                                JK TAS Jerry Airheads Page [ Parent ]

Re: motor conversion (3.00 / 0) (#8) by Jerry on Sun Dec 12, 2004 at 10:05:26 PM MST

Heres a picture of that genny.                        JK TAS Jerry Airheads Page [ Parent ]

Re: motor conversion (3.00 / 0) (#9) by christopher on Mon Dec 13, 2004 at 05:16:59 PM MST

Hi Jerry! Thanks for the pic and info.  This does look like the motor I used. I know nothing about motors or rewinding.  Tried this as a four pole when I first started with exsisting windings not knowing what it was and got no output.  So decided to try and rewind it myself as a eight pole three phase, and these were the results that I have gotten out of it.  I have run it at 2,000 r.p.m. and gotten 152 open DC volts on 12 volt battery load, 14.80 volts at 12 amps.  This is all star connected.  Was advised in a previous post delta is not good on diodes??  Thanks for all the help. Christopher       [ Parent ]

Re: motor conversion (3.00 / 0) (#10) by Jerry on Mon Dec 13, 2004 at 10:28:59 PM MST

Hi Christopher. Delta or star dosen't matter. What dose matter is exceeding the peak reverse voltage of the diodes. Star is basicly wiring the coils in sirese so the voltage is higher than the delta mode. Think of the coils in a generater/alternater/pma/converted ac motor or what ever you spinning and making electrical power with as being simular the secondary windings on a transformer. The diferance is your genny is equal to a transformer with many secondary windings. For example lets say you have a transformer with 4 sperate windings that produce 10 volts at 10 amps each. If you perelell all 4 windings you get 10 volts at 40 amps. If you siries all 4 coils you get 40 volts at 10 amps. The other posability is a combination of both or 2 coils wired in perelell this equals 10 volts at 20 amps. Now take the other 2 coils and wire them in perelell and now you have 2 outputs at 10 volts at 20 amps. You can now take these 2 groups siries them and end up with 20 volts at 20 amps. In any of the above configuration the wattage is the same. Amps times volts equals watts. 10vX40a= 400 watts, 40vX10a= 400 watts, 20vX20a= 400 watts. You reasigning or addjusting the coils to your needs. This is why I realy like the garbage dispoisal motor. The coils are loose and easy to see, change ajust, modify, connect or what ever you want to do. And you do the same with the start windings as well. A 1 hp garbage disposal motor is rated 10 amps at 120 volts this is 1200 watts and you havn't even accounted for the 600 watts or so available from the start windings. 1800 watts will never hapen from a Garbogen but I have seen 1200 watts. But 500w to 700w is a breeze for this motor with no rewinding nessary. And is dose startup in low wind. 120 volt motors are much closer than 220 volt motor for 12 volt charging. The problem with 3 phase motors is they have less amperage then single phase motors because there 208v/220v/440v or higher, very high resistance. Single phase become 2 phase any way.                          JK TAS Jerry                             Airheads Page [ Parent ]

Re: motor conversion (3.00 / 0) (#11) by Flux on Tue Dec 14, 2004 at 01:38:27 AM MST

Christopher From these figures and bearing in mind that you intend to chain drive it, I would try it in delta. I think it will match the 12v much better. Try this before you decide on the gear ratio of the chain drive. Good luck Flux [ Parent ]

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