Garbogen

[Turfdr]

I've got a 1/2 hp Emerson motor with 36 poles on the stator and 50 poles on rotor.

The rotor poles look to be close to 1/4" wide.

I was thinking I could machine the rotor down to almost 1/4" then mill 1/4" flats following the skewed poles and glue in 50 1/4"x1/4"x1" n42 magnets.

Then I remembered I already had 16 1/4"x1/2"x1" n45s.

Maybe if I glue 25 of these, after machining of course.

I wanted to get some opinions on if either one would work or if one way is better than the other before I buy more magnets or do all that machining.

Thanks.

[ghurd]

How about some more info on the motor and plan?

Single phase?  Name plate RPM?  Planning a rewinding?

I doubt you can use 50 neos.  Certainly can't use 25.

I would use the larger neos.  Easier.

G-

[Ungrounded Lightning Rod]

I assume you mean pole PIECES rather than POLES.  How many poles you have depends on how the rotor and stator are magnetized.  More than one pole PIECE will participate in each POLE and the rotor and stator will end up with the same number of poles.

The number of poles may not evenly divide the number of pole pieces on the squirrel-cage rotor, too.

You need to know the number of poles so you know how many magnets to put N up before you switch to putting S up and vice-versa.  And you want to leave a gap between the poles, rather than paving the whole rotor with magnets, when you do a conversion.  (Note that laying down the magnet next to the gap will be difficult because it will repel its pole-partners and attract the next pole, so it will want to jump into the gap.)

You can figure out the number of poles from the motor RPM and frequency rating.  On an induction motor RPM = (1 - slippage) * 60 * Hz / ( 2 * poles ).  Slippage is a few percent so the pole count is the even integer just over (RPM * 2) / (Hz * 60).

When you cut the flats for laying your rectangular magnets down, try to space the flats so you can skew the magnets to reduce cogging.

[Turfdr]

Ungrounded Lightning Rod

Yes, thats what I ment pole pieces.

The motor I have is 6.7 amp and does'nt have RPM on it , but search on this site took me here.

http://www.fieldlines.com/story/2004/6/8/201557/0741

http://www.fieldlines.com/story/2007/1/15/23411/0137

I think I understand now.I need 4 poles.

I don't know where I thought it needed to be N S N S came from?

ghurd

I agree I can't get 50 magnets in that space unless they were tapered at the bottom.

So if I lined up say 11 magnets N and 11 magnets S in groups and alternate them that would give me 4 poles?

What effect would the gap between poles have on output?

Thanks.

[ghurd]

The magnet grouping is related to the motor's pole count.

I figure the motor is probably either

a 1750 RPM (4 pole) and needs 4 magnet groups, 5 N up, 5 S up, 5 N up, 5 S up.

or

a 3550 RPM (2 pole) and needs 2 magnets groups, 11 N up, 11 S up.

The gap between the poles is not likely to make a lot of difference, within reason.

A couple pics of the coils would help.

G-

[ghurd]

Is this thing actually a garbage disposal motor?

If so, the armature is the thinnest I ever saw in one.  And the cleanest.

And I believe they are all 4 pole motors.

The "Certainly can't use 25" magnets is because the count has to be (should be) even.

G-