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Discussion Starter · #1 · (Edited)
Well, it might be more of a pancake motor, but I'm in the mood for pizza, and there is actually a reason for my choice of names. It looks about like this:



The "pizza" is the plastic or metal ring which forms the stator housing. It connects to the six thick slices of "pepperoni" which are the six coils arranged around it. They are wound on steel laminations like a transformer or solenoid, oriented vertically (parallel to the shaft). There are also six radial supports which hold a bearing for the shaft, which can be seen protruding from the top. It is protruding through a C-shaped section of steel laminations, which are positioned just above and below the surfaces of the coils, so it forms a continuous magnetic loop except for the gaps. There are also windings on these pieces, so the entire assembly is basically a transformer. ;)

I would drive this motor with a sequence of voltages on opposite coils, which will operate as electromagnets and attract the C-shaped armature to center on them. I would then apply the voltage to two sets, which should cause the armature to rotate and center on them. As I repeat this pattern the armature should rotate. I think it will work even without the coils on the armature. But they might be used like the shorted windings in the rotor of an induction motor. :cool:

I'm not really sure how well, or even if, this will work. But it is similar to some of the wheel motors I have seen, although most of them seem to have permanent magnets. I have some of the materials need to build this, and it seems fairly simple. Any magnetics and motor design experts out there to comment? Thanks! :)
 

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I am about as far from a "magnetics and motor design expert" as is possible but I think it is an interesting concept. I have been considering something similar except I see your 'pizza' as a three phase stator and the magnets as electomagnets powered by slip rings similar to an alternator. Control would be interesting but I think that field weakening for increased rpm would be much easier than for BLDC motors.

Edit: In rereading the OP I see little difference between the original proposal and my imaginings.
 

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Discussion Starter · #3 · (Edited)
It's very similar to a pancake motor and many brushless motors, but they all use permanent magnets. I want to make it purely an induction motor. But the windings on the rotor could be connected to slip rings which could supply DC and it could work as an alternator, or a synchronous motor.

Also the rotor and the stator could be reversed. In that case, the six coils could be replaced with magnets for a PM motor. The rotor could be a plastic or maybe aluminum disc with the magnets pressed in so it would be very smooth and have low windage. And instead of the coils on top and bottom, I might use toroid stator electromagnets with slots to accommodate the disc rotor.

I would probably encapsulate the magnetic components in plastic so the entire motor would look almost spherical or something like a yoyo. In general, it is best to keep magnetic loops circular, as toroids, or at least with smooth curves like a C-core transformer.

I've never actually made a motor except one of the simple homopolar motors I've seen on youtube using a AA cell, a rare earth button magnet, and a bent copper wire draped over it which spins:


And here is a pancake motor which is similar to my design:

 

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It's very similar to a pancake motor and many brushless motors, but they all use permanent magnets. I want to make it purely an induction motor. But the windings on the rotor could be connected to slip rings which could supply DC and it could work as an alternator, or a synchronous motor.

Also the rotor and the stator could be reversed. In that case, the six coils could be replaced with magnets for a PM motor. The rotor could be a plastic or maybe aluminum disc with the magnets pressed in so it would be very smooth and have low windage. And instead of the coils on top and bottom, I might use toroid stator electromagnets with slots to accommodate the disc rotor.

I would probably encapsulate the magnetic components in plastic so the entire motor would look almost spherical or something like a yoyo. In general, it is best to keep magnetic loops circular, as toroids, or at least with smooth curves like a C-core transformer.

I've never actually made a motor except one of the simple homopolar motors I've seen on youtube using a AA cell, a rare earth button magnet, and a bent copper wire draped over it which spins:


And here is a pancake motor which is similar to my design:

as for i know every brushless dc motors must have a driver.If this isn't true please correct me.your simple pancake motor also have driver.and as i see u have used arduino for it.My question is how did you make the bandages.And how could you decide its amount.And how could you make the commutation.
 

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Discussion Starter · #5 ·
The videos were not mine. They were only examples of the interesting but impractical homopolar motor, and a "pancake" motor that looked a little bit like my concept. You might want to contact the person who posted the video.

My design is for a three phase AC induction motor but it could also be made as a BLDC. In either case it would need a driver. I use Microchip products and not the Arduino, and I don't see a problem designing the circuitry or the PIC code. The magnetics are the part I don't fully comprehend. But I have been doing some simple experiments and then I'll have a better idea.
 

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Discussion Starter · #6 ·
I just found another video that is a rather good demonstration of how a three phase induction motor works. It uses six transformer cores and coils:


I may use a variation of this design, as I have a large number of 32 watt transformers and today I took one apart and reassembled it with all the E laminations facing the same way so as to create an electromagnet.

But I have thought a little more about the "pizza motor" concept, and here is what I have come up with:



This shows the rotor at 0, 15, and 30 degrees rotation. The pole coils start so that they are aligned, with maximum magnetic flux which takes a fairly short path between adjacent poles, rather than across the width of the rotor as in the example in the video above. I am hoping that the rotating magnetic field will induce current in the coils of the rotor which will cause it to move and generate BEMF as it approaches synchronous speed. At this point I am not concerned about torque ripple, which I think will be considerable. I am just trying to maximize torque.

One important feature of this design is its simplicity for manufacture. The coils are simply round bobbins on a round stud, which needs to be made of laminated iron. Since that is difficult to form into a cylinder, it could be a square cross-section with stacked laminations. The frame where the coils are mounted should also be laminated for good magnetic qualities. This design also could be stacked along the shaft, with multiple points of support.

Another idea I find interesting is to use ferrite or powdered iron for the magnetic components. It may be more fragile, but the parts could be molded into an epoxy resin or other material. The possibility that interests me is that of a high frequency motor for very high speeds and high efficiency. A two pole motor like this should run at 1800 RPM at 60 Hz, but ferriite might handle 60 kHz, which would be 1,800,000 RPM! :D

That is extreme, although there are motors that run at 1 million RPM. But this design might work for a large wheel motor or a bicycle rim motor, where possibly as many as 200 poles could be used. In that case, 60 Hz would be 18 RPM, but at very high torque. And if the magnetics can handle it, 6 kHz would be 1800 RPM, rather fast for a bike wheel! :eek:

Anyway, I think it will be fairly easy and fun to build a prototype. If it works (or even if it does not), I'll put it on youtube and share it. :cool:
 

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I just found another video that is a rather good demonstration of how a three phase induction motor works. It uses six transformer cores and coils:


I may use a variation of this design, as I have a large number of 32 watt transformers and today I took one apart and reassembled it with all the E laminations facing the same way so as to create an electromagnet.

But I have thought a little more about the "pizza motor" concept, and here is what I have come up with:



This shows the rotor at 0, 15, and 30 degrees rotation. The pole coils start so that they are aligned, with maximum magnetic flux which takes a fairly short path between adjacent poles, rather than across the width of the rotor as in the example in the video above. I am hoping that the rotating magnetic field will induce current in the coils of the rotor which will cause it to move and generate BEMF as it approaches synchronous speed. At this point I am not concerned about torque ripple, which I think will be considerable. I am just trying to maximize torque.

One important feature of this design is its simplicity for manufacture. The coils are simply round bobbins on a round stud, which needs to be made of laminated iron. Since that is difficult to form into a cylinder, it could be a square cross-section with stacked laminations. The frame where the coils are mounted should also be laminated for good magnetic qualities. This design also could be stacked along the shaft, with multiple points of support.

Another idea I find interesting is to use ferrite or powdered iron for the magnetic components. It may be more fragile, but the parts could be molded into an epoxy resin or other material. The possibility that interests me is that of a high frequency motor for very high speeds and high efficiency. A two pole motor like this should run at 1800 RPM at 60 Hz, but ferriite might handle 60 kHz, which would be 1,800,000 RPM! :D

That is extreme, although there are motors that run at 1 million RPM. But this design might work for a large wheel motor or a bicycle rim motor, where possibly as many as 200 poles could be used. In that case, 60 Hz would be 18 RPM, but at very high torque. And if the magnetics can handle it, 6 kHz would be 1800 RPM, rather fast for a bike wheel! :eek:

Anyway, I think it will be fairly easy and fun to build a prototype. If it works (or even if it does not), I'll put it on youtube and share it. :cool:
waiting for your good news :)
 
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