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coil testing ???????
By JB, Section Homebrewed Electricity Posted on Fri Mar 12, 2004 at 07:17:45 PM MST
coil

Im testing a coil for a dual rotor clone 12 magnets on each rotor. Im only using one rotor with 12 magnets for the test as im not ready for the second rotor. i chucked up the rotor in my lathe and set the rpm for 266. my coil is 25 turns on number 16 wire taped right hard up against my tool block that is about 2 inches thick steel. im getting .57 dc volts on the plus and minus side of the bridge rectifier. question 1 will this double when i put the other rotor on. question 2. im showing 12.5ma amps with my meter in the 200ma scale out of the bridge rectifier. I wont read in the 10 amp scale yet. is that like a 1/8 of an amp??. will this go up with the other rotor on it. If i find some 18 gauge wire will these both of these go up or just the voltage. I dont have much wire to burn up for a lot of tests. Any suggestions. Thanks JB

coil testing ??????? | 3 comments (3 topical)

Re: coil testing ??????? (none / 0) (#1)
by DanB on Sat Mar 13, 2004 at 07:58:06 AM MST

hi JB -

just curious, for what voltage is this machine? Which size magnets are you using?

I would expect the voltage to double, when you add the 2nd rotor.

I wonder how large the prop will be that your planning.

The numbers you suggest (after the voltage is doubled with the 2nd rotor) would seem in the ballpark for a 12 volt machine wired in Star, but the resistance of the 16 gage wire might be on the high side. Would the same number of windings fit if you used heavier wire? The last few we've made are using the same number of coils, and the same number of windings (25 per coil) but were using #11, or #12 wire. If the wire you use is too fine, it may be inefficient at higher outputs, and it may overheat and burnup in higher winds.

Re: coil testing ??????? (none / 0) (#2)
by RatOmeter on Sat Mar 13, 2004 at 07:59:13 AM MST

It'll probably better than double, with the second rotor completing the magnetic circuit fully.

12.5 mA is 1/80th of an amp. It seems pretty low.

What is your air gap?

What kind of magnets are you using?

-RatOmeter

Re: coil testing ??????? (none / 0) (#3)
by JB on Sat Mar 13, 2004 at 11:45:55 AM MST

hello Dan and Rat. the airgap is as close as I can get it. i had to lock down the crossslide to keep it away from the magnets but it is super close. The magnets are 1 1/2 by 1/4 thick on 3/8 rotors 9.5 in diameter. They are some steel disc out in the yard i had. it wont have the 5 studs to adjust the airgap but will be machined down to the gap I need. Im not sure on the voltage but I prefer to make it where I can change from either 12 to 24 volts depending where I put the tower and how high. The test coil improved considerably. I had a 1 1/2 hole in the center for the magnets. that read .57 volts. I squeezed it down to 1 1/4 hole and it improved to .80. One think about the lathe you can test the in and out also.pretty cool. One thing that has me stymied a little is that this test coil is for a single phase size. I a will be goin 3 phase so the coil is a little wider. I hope 3 phase is better. Im just takin peoples word for it as I dont really understand how 9 coils though bigger can be better than 12 coils.Im going to build another jig and coil soon and bump it up to 50 turns flat but wide. Im going to try to keep the total airgap down to 5/8 due to the smaller neo magnets. I was lookin at the pig machine . I built a 3 blade 6 foot6 inch rotor for another machine last year. that is what i am goin to put on this.Im trying to get my numbers better before i do my casting. Woops my galpal has to use the phone. So Long for now. Thanks JB

coil testing ??????? | 3 comments (3 topical)

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