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self excited homopolar generator (no PMM!!!)

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Salvador

Tue Apr 07 2015, 06:48PM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Right the charge is being pushed sideways so to speak not directly in the very direction the magnet travels.

So when I now visualize this in my drum type homopolar generator , well i have the exciter coil wound on the stator and the load coils on the stator , the stator itself imagine to be sort of similar to that of an AC induction motor, only difference would be the way the coils on it are wound .and there is a drum rotor ,the way I imagine the rotor is copper foil or flat litz wire wound in a toroid like manner forming a loop , well imagine a toroid transformer for better understanding and now kinda make it longer sort of strecth it out and put it centered on a rotor piece.

the question im trying to solve in my head is would this follow chain of events take place the way I imagine it to be ,

The Rotor spins up and rotates , I apply a current kick to the exciter coil which has a capacitor in series with it , the current in that coil form a small magnetic field the rotor spins through that field (AC fiel) there is now current induced in the rotor windingthis now forms a larger field and this larger field from the rotor now charges the capacitor in the exciter field coil and also induces AC current in the other load coils on the same stator , but since the way the coils are oriented towards one another , I am hoping to not only get the induction of current due to the changing field itself (transformer effect) but also the additional boost of current due to lorentz force on the charges , so im hoping to in each cycle get the induced current +the boost of lorentz current which is basically the same current just amplified due to the lorentz forces from the onpassing field of the rotor , these two currents being in phase ine each cycle.

Hard to explain I hope you understood the idea this is also the answer to your question about the motivation behind these questions , just an idea that's all.

Uspring

Wed Apr 08 2015, 10:11AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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A bit confusing. Can you make a drawing?

Salvador

Wed Apr 08 2015, 09:45PM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Well I'm not good at drawing actually im bad at that.

I will make a drawing soon with one of my friends helping me out but meanwhile I want to show you something very interesting I found searching on google.Although a bit different it pretty much seems to be the same thing im talking about here , can I ask you guys a favor , I will attach the PDF file can you please take a look and tell me what you think.

As much as I understand they have a flat field coil close to the center axis which is fed with DC current so makes a DC field then there is a faraday disc like rotor with blades , the disc part rotates in the DC field coil and the blades extend the " induced" magnetic field in the rotor to the periphery where the double sided circuit board windings are.I assume tis machine must induce current in those outer windings by means of induction as in classical generators and also by means of lorentz force as the layout is like a faraday homopolar generator.

But the interesting part is not that the rotor which has non uniform structure can induce current into further windings because when it rotates it makes the windings to see a variable field, the interesting part is how does the rotor disc gets its magnetic field , it's said in the paper that it gets it from a field coil which is quote :" fed with DC"

So does this macine work because the spinning rotor is a magnetic continum of the DC field coil and because it has uneven sides the magnetic field seen by the armature windings on the cirucit boards is changing since the blades move past those windings so there is current induced in them , so this is a kind of AC homopolar generator with no brushes and slip rings , correct?
]axialflywheel_ieee-ias_2002.pdf[/file]

Andy

Thu Apr 09 2015, 02:44AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Hi Salvader, look up axialflux wind turbine genny, its the same princple but with a dc electro magnetic instead of Neos, but by the looks it would make a good genny, the field strength would be weaker, as the magnetic path is spreadout, but it is mechincal good so should beable to get high speeds, compared to the axial flux.
If your going to build this pdf, make the steel top and bottom rotor thinkness as large as possable, and large radius, with the airgap were the coils are in the centre, less than 1cm between top and bottom electromags, and it would make a good about 12-24 volt 30amp setup.

Edit
It also remindes me of a car alternator, if the slots didnt match up from top to bottom, you would have n,s,n,s and get double the voltage as the magnticfield ampultude is changing twice as quick, but iI would move the feild coil to the outside to make the magntic path from high,low,exra high,low,high too low,low,extra high,low,low which should increase the maxiunim ammount of amps possabile from the device.

Uspring

Thu Apr 09 2015, 08:30AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Looks like a more or less synchronous motor to me. As they say:

The torque is created by interaction between this field and the rotating field produced by the three-phase armature winding.

The geometry is interesting, though.

Salvador

Thu Apr 09 2015, 08:37AM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Well I will not build exactly this I have something similar yet different in mind.
why you say it's a synchronous motor? doesn't all synchronous motors have a direct electrical path between their stators and rotors , hence the brushes hence called universal motors that can work both on DC and AC?

Wolfram

Thu Apr 09 2015, 09:11AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
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Posts: 971

What's the goal of the project? It will probably be easier to visualize the idea if we know what the purpose of it is.

Salvador wrote ...

Well I will not build exactly this I have something similar yet different in mind.
why you say it's a synchronous motor? doesn't all synchronous motors have a direct electrical path between their stators and rotors , hence the brushes hence called universal motors that can work both on DC and AC?

A synchronous motor has a rotor (permanent magnet or iron in the case of reluctance motors) that is locked to the rotating field generated by the incoming AC frequency. A universal motor is not a synchronous motor, but a brush-commutated motor, like toy DC motors, but with an electromagnet for the stator.

Salvador

Thu Apr 09 2015, 09:54AM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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right correct I mixed them up , synchronous and asynchronous are words that refer to the way the field aligns with the rotor,
a universal motor is a synchronous motor, yet not the only case.

Salvador

Sat Apr 11 2015, 07:56PM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Posts: 86

Now I guess my final question for now would be , if you are familiar with the machine described in the PDF i added in a few posts above , there you see a rotor with "blades" having a magnetic field in it excited from a DC field coil , the blades pass by the armature windings creating induction current in them, the authors describe that as an AC homopolar generator due to the geometry of the machine also lorentz drag is induced in the windings as the blades pass,

what I wonder is what would happen and how would it work if I changed these things, make the rotor a two sided dish, no blades just a uniform dish like circle inbetween put a field coil and at the outer sides put the armature windings that part being the same as in the machine described above. Now run AC current through the field coil , the dishes or the rotor rotates and so now it has changing flux through it would the armature windings between the dish get both induced current and also lorentz drag in each cycle as in the original machine where the rotor has uneven geometry or blades?

just in case someone cant see the original PDF here it is one more time

Andy

Sat Apr 11 2015, 08:37PM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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What are you after, volts current or power, the ac will make more volts, as you have motion aswell as magntic field ampultide changes, but the current max will be minial because a inductor stores more and more energy in the feild towards dc, its like motor gears, one is hardened steel the other a liquard, the transfer mechinics is bad, as the power is volts times current, you could spin it upto the speed of light and beable to extract as much power as a electrostatic machine, but you would have gigavolts to use.

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