4 pole induction motor

[Devo]

First off a big thanks to those who told me how to move my 3 jaw chuck on the backing plate to centre up my lathe I am within 5 thou & will tweak it in better yet.( was out more than 60 thou before)

I have turned down the rotor & used permatex cold weld to adhere the magnets.

I put 4 #29(thanks NTL) mags around the rotor

I will post results & pics later. I want to remove the rotor & try 8 mags to see the difference. If I go nn ss nn ss  my rotor will be 4 pole like the coils with some cancelation as the magnet mass will be bigger than the hole. If I go n s n s n s n s around the rotor a n & s pole will be on opposite legs of the coils some times but also a little cancelation.

I am wondering if any one has done this before to save me trying both ways to achieve maximum output using 8 mags.

Should I try 6 mags as well n s n s n s to post results?

Thanks for any input on the most efficient layout.

Devin

[Flux]

If it is a 4 pole winding you must have a 4 pole rotor. If you want to double up on the magnets you have t use NN SS NN SS. If the core is not saturated you will gain, if it is saturated you will see little improvement.

Flux

[vawtman]

Flux what would his signal be that the core is saturated?A paper clip sticking to the shaft?Thanks

[Flux]

There is no easy way for you to know the flux density in the core except by the voltage you get at a certain speed.

The first place to saturate is the core teeth, when this happens you still get some increase in volts but it needs a lot more magnet to produce a few more volts.

I haven't done anything with motor conversions but from experience with wound field machines, I suspect some of the conversions must be near saturation at least in the teeth.

I am inclined to suspect that with curved neos that fit the rotor and stator curvature and covering 2/3 of the pole pitch, you will be close to saturation with magnets 1/4" thick.

Using rectangular blocks which don't fit the curvature and leave large air gaps may require a lot more thickness.

From the output point of view, taking the teeth into saturation is good, but it will give more iron loss. Like all things there is probably an optimum between low speed performance and maximum output.

 Flux

[Devo]

Thanks Flux, one thing I don't quite understand is when doing the axial flux wind genny it was best to have a north magnet crossing one leg of the coil when a south is crossing the other. I can acheive this with 8 magnets going n s n s n s n s.If I was to find the wire going from each coil to the next & "pull" it out so that each coil was individually rectified would there be any benefit to going that way versus nnssnnss?

If not I will stick with the 4 mags because 1 magnet just fits the centre of the coil so 2 side by side the same polarity would cause alot of cancellation.

Is everyone elses world like mine , I finally get my lathe ,get it working , get some glue that will hold the magnets on , get the rotor turned down & magnets attached & start to assemble & I can't find the back half of the motor ..aaahhhh :-)

Thanks for all the help

Devin

[Devo]

Got the motor conversion complete using 4 mags , I am quite happy with the outcome.

both sets of 4 coils go into there own bridge rectifier so I have 2 rectifiers.

If I wire them in series I get 37 volts at 210 rpm (open) this will put about 2.9 amps into a 12 volt battery at 13 to 14 volts at at 280 there is little improvement at 350 about 3 .2 I believe

In parellel I can't remember the open voltage but it was 2.5 amps at 13 volts at 210 rpm. 3.2 amps at 15 volts at 280 & it would make my drill press cut out at just over 4 amps at about 15 volts at 350 RPM so an easy 60 watts at 350 rpm , cogs pretty hard though. , I may through an 8 foot set of blades to catch low winds & start easy

& make it furl out of the wind early.

I forgot to try it as a 2 phase through 1 bridge , maybe after supper.

I also never put bearings in it just left the oil bushings so that may be increasing drag as well.

Devo