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LAN_403

Salvador

Sat Jun 20 2015, 04:58PM

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

well im starting to think that way , the biggest problem would be to make the field coil attachments because one end needs to be physically part of the stator while the other pole has to have a magnetic path around the staor into the rotor

to get anything uself out the airgaps for the flux paths to the rotor would need to be as small as possible ,

but when you think about it what does your intellectual guess say ? does it even sounds plausible because if it's not working in theory why should I waste time and money to try it in real life thast why i'm asking before.

Ash Small

Sat Jun 20 2015, 05:42PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Even if the gaps aren't 'ideal' you should still be able to measure what's happening.

I'd start by finding a toroidal core. Once you've decided on that, sizes of everything else are easy.

Salvador

Sat Jun 20 2015, 06:04PM

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

i have an idea to just get an old induction motor strip of its coils and wind it toroidally , where wires in one direction go through the slots where the coils normally are located and come back through the outside and into the slots again ,
i could cut the rotor on both sides to make it more simlar to the one in my drawing, anyways ash why you didnt say what your thoughts are on the theory of this idea? is it even worth trying or do you honestly don't know , I would like to hear your and ofcourse other's opinion on the mater.

Ash Small

Sun Jun 21 2015, 10:24PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I don't fully understand what you are trying to do, so I suggest you build a 'model', apply some small AC signal to it, spin it up, and use any old 'scope to 'see' exactly what happens

I used to make simple electric motors as a kid by winding the rotor windings around pieces of wood, using nails as bearings. the commutators were the only 'tricky' bit, but I used to just use copper wire and I got acceptable results (they used to spin pretty fast)

You could spin yours up using a belt and a couple of pulleys. Large elastic bands can be used as drivebelts if nothing else is to hand.

radiotech

Thu Jun 25 2015, 08:49AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546

Consider a 6 pole, wound rotor synchronous motor, which is being started
on a 60 Hz power line. As it starts the rotor is connected to slip rings. and
resistors are attached to the slip rings.

Just as it starts, the rotor is the secondary of a very large transformer. As it
moves, there is a high frequency current produced in the resistors. As it
speeds up, the frequency of this current reduces. As it approaches the speed
it is intended to run at, the rotor current approaches DC.

In practice, an automatic relay operates at a precise moment as the rotor
current approaches DC, and the resistors are switched out, and a DC power
source, is connected. At that moment the speed of the motor locks on to
a sub multiple of the power line's angular velocity.

Somewhere in this description, your idea for a machine may lie.

Perhaps there is a training video on line about synchronous machines.

A Vulcan mind-meld with those who have actually experienced the
ills and joys of such machines would help too.

Salvador

Thu Jun 25 2015, 02:10PM

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

Well not a very common motor the one you described , well actually i believe very similar except for the comuttator with brushes instead of slip rings and brushes is the universal motor , it too ahs a wound rotor , just that instead of the rotor behaving like a bar magnet that locks and fol;lows the mains frequency it constantly pushes itself against the field of the stator.

well my idea is actually much simpler than these, instead of having poles you just arrange a coil in a way that the flux cuts the wires that go only in one direction , then you vary the flux density along the length of the coil to have induction at all, and then you can vary the flux itself with a certain frequency and waveform and this variation should mirror in the output from the coil.
the very key being that the output follows the waveform and frequency of the input field coil signal.By doing this one can adjust the generator to its load by just adjusting the frequency.
in a local AC grid this would require an AC to DC inverter to then convert the output to the grid 50 or 60hz. Or you just have to run the generator itself on 50hz Sine wave. but in places like submarines, airplanes and other areas where small lightweight generators are needed or HVDC lines the high frequency AC output could just be rectified and then fed into the grid.

Salvador

Thu Jul 09 2015, 08:31PM

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

So I'm back as some of you suggested and as I thought myself I made a prototype.I kinda lame one but it has the things I think it should have.
I havent yet fully tested it only half way there and I have some doubts about whether it would work as I want it to work or work at all, but I want to give you some pictures and ask what do you think?

the welded screws attached to the stator are meant to be magnetic flux paths from the field coils to the rotor, as the idea is to have the flux go through the airgap at the rght angle so alike poles are faced both into the rotor and the other alike poles are forced into the stator and they should meet through the airgap.
the rotor has a shape that when it rotates it drags the area of high flux density around the stator.

i couldnt post the pictures here because the filesize was too big.

mister_rf

Sat Jul 11 2015, 08:36PM

Registered Member #4465 Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145

Well, if you donâ€™t increase the number of turns in the coils, there will be no success. IMO try at least fifty time more than the actual design.

Salvador

Tue Jul 14 2015, 05:53PM

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

sadly it doesnt work , even with such little count of turns on windings i ashould have got atleast something on the meter.
maybe its due to the geometry of a ac induction motor's stator where the windings are kinda into the stator and the part that first encounters the flux is the stator metal itself, or maybe my idea doesnt work.

but theoretically everything should work, one pole is always in the stator , the other pole in the rotor , the rotor geometry is shaped as in pictures so that as the rotor rotates the areas of high flux rotate with it , the signal into the field coil is AC.the output coils should get induced current o the frequency of the field current but magnified due to the fact that the rotor stator airgap has a varying and physically moving flux.

sadly most poeple whom i have asked are not interested into thinking about it.

Ash Small

Tue Jul 14 2015, 06:44PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I suggested building something simple from scratch, starting with a toroidal core. I think your present setup is prone to leakage inductance.

I'm not saying your idea will work, though, just trying to give some 'constructive criticism'.

As you point out, I would have expected the meters to indicate something.

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