Stator ring question

Hi Stephen,

I worked in R & D at a solenoid and electric motor company for about 15 years (military, aerospace and space applications). It was all leading edge technology projects. I guess first of all I would have to say that your question is to vague. Magnetic strength is measured in gauss or force so you need to know what kind of gauss/force you are trying to achieve or torque I guess since it appears you're working on a motor. Gauss is directly proportional to the force a magnet exerts. Permanent magnets come in a large variety of sizes and gauss. The gauss/force reading will change at an exponential rate with respect to the distance your mating part is from the surface of the permanent magnet so for optimum performance you will want to run extremely close clearances between your mating magnetic fields. Your number of windings/wire size will vary with what kind of force/amperage requirements you are trying to achieve. Force = Amps. x #Turns.

If you're really serious about this project let me know. E-mail me and I will give you the name and number of a motor EXPERT.

Good luck and have fun,

Bill

wfanestil@msn.com

Hi wfanestil, I have a question that's been bugging me for awhile. I know that DC motors have (ie. starters) the permanent magnets on the outside of the shell and generators have the electromagnets on the rotor. Has anyone built a generator with rare earth magnets combined with with coils on the rotor?? I'm thinking that the combination would increase the magnetic flux (old school) with a lower amp draw with increased output. (I know of a lost field. as we would have to flash the rotor when lost.) Is the rare earth magnet too soft or mechanically unsound to handle the rotational speed? Could a lower speed be used as the strength of the field would be so much higher?

Just thoughts

I don't know about building a generator with rare earth magents from scratch. They do have motors with permanent magnets for fields you might try to modify. That might make a good start for you if you can't do it from scratch. A few of the 40KW standby generators that I have worked on would lose their residual magnetism for some reason after sitting idle for a month or two. They would not have any residual magnetism to excite the generator to start it generating. We drilled the stator, epoxyied and peened the stator tight around the magnet to hold it in place and that would give the fields enough "kick"to start generating. So I know that works.

Brushless DC motors have permanent magnets in the rotor, and coils in the frame (stator). They can be used as alternators, with the output rectified to dc if desired. Many brushless DC motors are highly efficient, presenting little need for supplementing the magnets with coils (which would then require the complexity and wear of brushes.

These motors can operate at quite high speeds.

Thanks Blink for the info. I was kind of wondering about combine the two. No pun AC/DC sorta. I was thinking of a winding added to the rare earth magnetics to enhance the flux density. (Gauss??) The idea is to have a slower moving rotor, (more poles) to equal the same output of a faster moving field. I think they are verse visa'.

OK need more beer!! LOL

I have a 12v 3amp power supply, a two way ac switch for the stator ring to make the magnetic field rotate, and 17 gauge wire. I am trying to get a magnetic field that is about the same strength as one of those neodymium magnets that you can pick up from ACE. They are called "super magnets" and their dimensions are 12mm*3mm) disc magnets. So is there a way I can find out how many gauss these magnets are and is there a formula I can plug that value in so I can figure out how many windings to put on each of the four notches on my steel stator ring?

Thanks for the reply.

Stephen

Hi,

Field strength of modern magnets (SmCo and FeNdB) is above 1 M amps/meter.

So if you wind a coil around a magnet in an existing design and the magnet has a length of 10mm for example then you would need 10,000 (ten-thousand!) amps to double (or null) the magnet. Unobtainable!

This difficulty is existing too in magnetising modern magnets as 4 to 7 T is needed and with B(in Tesla)= µ_o(permeability of vacuum) times H(field-strength in A/m) the required current!

Get more magnets if needed.

Below: 2phase motor/generator (1 design flaw)

RHABE