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Author Topic: Constant flux DC motor/generator.  (Read 26096 times)

broli

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Constant flux DC motor/generator.
« on: December 14, 2009, 01:08:05 AM »
I'm glad to present the latest design being a result of all my homopolar research thus far. This design uses some very basic concepts and principle to make a motor or generator. The crucial part is the understanding of a homopolar motors/generators.

A lot of people have tried numerous methods trying to either have a motor without back emf or a generator without back torque but most attempts have been in vain. My research has lead me to believe that this is possible if the flux is contained rather than radiating freely. Thus far I have seen only one design where this concept is exploited with success. Here I present my own design, first as a proof of concept for table top experimentation and second as a complete unit for continuous power generation.

The motor part generates no back emf when operating since the magnetic part is rotating instead of the conductor part, this is because of newtons third law (the conductor torques the magnetic part and the magnetic part counter torques the conductor). The speed limit thus depends on the components and friction. The generator part on the other hand produces no back torque since both conductor and magnetic part are attached to each other. Since the conductor part that is farther from the axle is moving with a higher linear speed (because v= angular speed * radius), this will overpower the emf caused by the inner part exposed to the field and create a net emf.

In the first attached image the proof of concept of the motor is explained. This needs two C-cores and either a magnet or electromagnet (EM's are more preffered since you don't need to cut the core) to produce the field.  Then a conductor passes this field twice, twice generating what is mostly known as the lorentz force. On both pieces the force is equal but in opposite direction. Using simple leverage law you see that this creates a net torque on the system. and the conductor rotates. The conductor will be drawn into the field and pushed out every turn. Since the field is only present at the air gap the rest of the conductor is not affected.

In the other 3d renditions a possible complete motor design is shown. For the sake of clarity half of the ferromaterial has been cut away. Both rotor and stator are indicated. As you see the rotor is the magnetic part while the conductor is stationary, hence no back emf. This is just one design out of many possible others. There is no limit here, a different design can for instance use a ring magnet. The main principle would remain the same that is....

Flux cutting small radius produces small torque, flux cutting at bigger radius produces bigger torque.

Flux has to be cut two time in order for you to return to the same point. This is like drawing a circle and putting your pen in the middle of it, If you leave it you cross the circle, if you want to go back you need to cross it once more. Our key here is that we can cross it at two different points so a torque can be developed.

I hope people will at least try the proof of concept out to confirm the principle.

lumen

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Re: Constant flux DC motor/generator.
« Reply #1 on: December 14, 2009, 03:12:44 AM »
In the proof of concept example, the outer field would have leverage, but for a shorter rotational distance. After the wire is out of the outer field, it is still in the inner field and would want to rotate back.

The second motor design is much better. However, now things have changed! The same magnetic field is traveling through both gaps. The outer field gap's surface area is much larger than the inner gap's area. This means the inner field will be much stronger than the outer field and will be possibly exactly the potential to rotate either way or not at all!

Maybe you see it differently?


broli

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Re: Constant flux DC motor/generator.
« Reply #2 on: December 14, 2009, 04:13:52 AM »
Let's say the material can be saturated and remains saturated even without a EM or PM. Wouldn't it now be reversed. Since you have more magnetic domains at the bigger radius and thus a bigger net field. The ferromaterial is the crucial part not the magnet.

Only experimentation can reveal the truth. It takes a 5$ circuit to measure accurate field proportionalities.

jadaro2600

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Re: Constant flux DC motor/generator.
« Reply #3 on: December 14, 2009, 02:22:28 PM »
Animate?

I'm not sure what's attached to what given the cross sections.

I have a constant flux where magnetic field stays attached to the rotor, and the magnet spins, unfortunately, the design relies on gravity and it's 'wounded' axis to throw it over the tendency for it to want to align with the outside wire ( yes, the 'reference' frame ).

broli

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Re: Constant flux DC motor/generator.
« Reply #4 on: December 14, 2009, 02:26:08 PM »
Animate?

I'm not sure what's attached to what given the cross sections.

Did you not see the labels? They make clear which parts rotate and which parts stay stationary. An animation is overkill just to show the rotor part spinning.

broli

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Re: Constant flux DC motor/generator.
« Reply #5 on: December 14, 2009, 06:35:22 PM »
@lumen: You may be right about the flux being more dense towards the center. Below is a different design that uses the same flux density between two gaps.

The idea is that the left gap will cause a force on the conductor and a reaction force on the magnetic parts, while the right side will do the same. One can then deduce that the left side of the magnetic part will be affected by the left part of the conductor and the right side by the right side of the conductor. Using this knowledge one can make these parts to rotate freely on an axle to produce unrestricted rotation.
« Last Edit: December 14, 2009, 07:01:11 PM by broli »

leeanderthal

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Re: Constant flux DC motor/generator.
« Reply #6 on: December 14, 2009, 08:33:38 PM »
I don't believe that any of the designs will have BEMF or back torque.  But, I believe that for much different reasons.  Since the conductor crosses the field twice, there is no net current produced.  It is cancelled out.

Lee

broli

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Re: Constant flux DC motor/generator.
« Reply #7 on: December 14, 2009, 08:41:38 PM »
I don't believe that any of the designs will have BEMF or back torque.  But, I believe that for much different reasons.  Since the conductor crosses the field twice, there is no net current produced.  It is cancelled out.

Lee

This is correct, the last posted design does not operate as a generator only as a motor, where the magnetic source rotates instead of the conductor. The previous designs could have been a generator IF the fields where equal, but as lumen pointed out this can not be necessarily the case...but the proportionality can always be tested with a 2$ hall sensor and a voltmeter.

leeanderthal

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Re: Constant flux DC motor/generator.
« Reply #8 on: December 14, 2009, 08:53:33 PM »
Quote
This is correct, the last posted design does not operate as a generator only as a motor, where the magnetic source rotates instead of the conductor. The previous designs could have been a generator IF the fields where equal, but as lumen pointed out this can not be necessarily the case...but the proportionality can always be tested with a 2$ hall sensor and a voltmeter.

I don't see how the last posted design can operate as a motor as the conductor again is crossing the field twice.
All of the designs have a couple of other problems as well.  Mechanically they would be impossible to build unless you could figure out how to levitate some of the components.  Electrically, way to much internal resistance (dead wire).

Lee

broli

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Re: Constant flux DC motor/generator.
« Reply #9 on: December 14, 2009, 09:03:50 PM »
I don't see how the last posted design can operate as a motor as the conductor again is crossing the field twice.


 Yes and? Have you forgotten newtons third law. Action equals -Reaction. The conductor, which remains stationary, is acted upon by forces of the magnetic material. The magnetic material are acted upon by the reaction force of this. You perform some simple rules to get the forces and reason will tell you that the left part will mainly be affected by the left conductor side crossing the flux and the right part by the right conductor side. Hence the rotation of both sides albeit in opposite direction. If you don't get this logic then I can't help you.
 
Mechanically they would be impossible to build unless you could figure out how to levitate some of the components.  Electrically, way to much internal resistance (dead wire).

There is nothing to figure out except for experimental data, I annoted everything clearly. The parts you think that should be levitating in the first design are either stationary in motor mode or glued to the rest in generator mode. My designs are meant to inspire and explain the concept in a very general way, not present an autocad and CNC ready model.
 

leeanderthal

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Re: Constant flux DC motor/generator.
« Reply #10 on: December 14, 2009, 09:26:01 PM »
@ Broli
Sorry, It is not my intention to rain on anybody's parade. I just tend to think in terms of practicality.  I fully appreciate your thoughts and solutions for the puzzle at hand.
I can see how the posted design could work as a motor.  But why not a generator?
Do you believe that as a motor it would not have BEMF because of a uniform field?

Lee

broli

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Re: Constant flux DC motor/generator.
« Reply #11 on: December 14, 2009, 09:37:23 PM »
As a generator you would need to rotate the conductor loop. If you start rotating the loop, in the last design, the wire pieces between the two gaps will generate an EMF. But since the direction of speed and their magnitude are the same AND the direction of field and their magnitude are the same they will both generate an EMF that cancels the other thus there would be no net EMF. This is like moving a rectangular conductor loop in a constant uniform field. You can see that the single wire pieces do get polarized but in a loop they all cancel out. So this is why it probably won't generate. You can heavily modify it and make it generate but then you will end up with a homopolar motor with back torque....as far as I know. Nothing I say is fact even if it's something very obvious, that is why I would like to encourage others to get involved and get the experiments out.

leeanderthal

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Re: Constant flux DC motor/generator.
« Reply #12 on: December 14, 2009, 09:53:32 PM »
I was thinking that as a generator not rotating the conductor loop but rotating the left and right components in opposite directions.  Just as it would operate as a motor.

Lee

broli

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Re: Constant flux DC motor/generator.
« Reply #13 on: December 14, 2009, 09:55:07 PM »
I was thinking that as a generator not rotating the conductor loop but rotating the left and right components in opposite directions.  Just as it would operate as a motor.

Lee

this would do nothing. Just like in a homopolar generator rotating a magnet in front of a stationary disc.

leeanderthal

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Re: Constant flux DC motor/generator.
« Reply #14 on: December 14, 2009, 10:16:47 PM »
Ok, if you were to take the magnets out of the center of you design and place them around the rims of the left and right components with opposite poles facing each other.  I think that it would then operate as a generator.  How would this then affect the objective of your design?

Lee