Homebuilt handmade "3 phase" electric motor

[skimask]

Yep, but you will not need the insulator. The current created and suppressed in the copper is the magnetic insulator.

I meant that in terms of electrical insulator, like a thin piece of plastic or something.

Attached is a bad drawing of what I mean.

Yep, that's what it looks like, roughly...same idea all around.

I wonder, if and when I get this thing going, how much power I'll be able to pull out of it.
Rebuild it, put a bigger shaft in it, beefier wiring, bigger copper, and so on and son on...
I wonder what the limit would be...on a beer budget anyways...

[mackrackit]

Well ,on a beer budget the aluminum could be used in place of the copper

Really, I do not think there is a limit. Time maybe. I have been working on a 1KW wind machine for awhile now. Permanent neo magnets, quad disk rotors 3 phase each, 6 foot turbine.

Get a little money, get a little time...

[skimask]

Do I even have my nomenclature correct for this type of motor?
Is what I'm trying to build really a 3 phase AC synchronous motor?
Or is it really an induction motor with 3 driving phases?
I did some more reading and it almost seems like an actual 3 phase AC synchronous motor has a powered rotor, with the 3 phases on the rotor and the 3 phases on the stator out of phase, and it's that out of phase that makes it turn.
And I'm still trying to get my head around how that 'shorted rotor' with all of its 'shorted' copper bars and wires actually generate that 'counter balancing magnetic force'... Got my left hand out with the 3 fingers pointing every which way...maybe I should use my right hand?

[mackrackit]

Do I even have my nomenclature correct for this type of motor?
Yes and No

Is what I'm trying to build really a 3 phase AC synchronous motor?
No, You are building an Asynchronous motor. Synchronous motors need to be spin started to bring then up to sync speed. The starting motor is called a "pony" motor. Or a wound rotor can be used. These are not common because of the cost to build and the controls needed.

Or is it really an induction motor with 3 driving phases?
Yes, Because a EMF in induced at the rotor. In the US we speak of single and three phase, but what about two? This is what adds to the confusion. I would guess your water heater runs with two 120 volt legs, ths is really two phase. Look at vector diagrams for "delta" and "star" sometimes called "Y" to get a visual on it.

I did some more reading and it almost seems like an actual 3 phase AC synchronous motor has a powered rotor, with the 3 phases on the rotor and the 3 phases on the stator out of phase, and it's that out of phase that makes it turn.
Yes, see above.

And I'm still trying to get my head around how that 'shorted rotor' with all of its 'shorted' copper bars and wires actually generate that 'counter balancing magnetic force'... Got my left hand out with the 3 fingers pointing every which way...maybe I should use my right hand?
You may have to take your shoes off for this one one hand will not work

I scaned a few pages from one of my books "Electrical Circuits and Machinery Volume 2 Alternating Currents" Copyright 1942.

I hope you will be able to read it as the pages are getting somewhat on the yellow side.

Again there are two ways of looking at this. Both using the "shorted" idea.

1- Because of the multiple shorted circuits a large current is produced on the rotor, giving a large magnetic flux. This causing the iron between the copper to become a magnet.

2- If an iron bar is placed in a magnetic field it will take on the prperties of the magnet with one end being "N" and the other being "S". If the maget is rotated the iron bar will rotate too. The large current between the iron bars on the rotor act as a shield so each piece of iron has properties independant of the other.

Visualize the setup from the end with four poles . Every 90 degrees around the stator at any point in time there will be N,S,N,S. Looking at the rotor as a whole, an inductor with multiple high current shorts.

The thing with 3 phase and 120 degress between each phase mahes a rotating field with lets say very small gaps. You might think of a stepper motor setup with very small steps.

Single and two phase motors need an extra winding to start to "throw things out of phase" and some times to keep things out of phase. ( built in phase converters ) Start caps and run caps are sometime hooked here.

I hope I am not making this more confusing.

[mackrackit]

More from the book.

[skimask]

Synchronous motors need to be spin started to bring then up to sync speed. The starting motor is called a "pony" motor.

A couple of extra windings or something on the end, just enough to give it a bit of a kick?

Because a EMF in induced at the rotor. In the US we speak of single and three phase, but what about two? This is what adds to the confusion. I would guess your water heater runs with two 120 volt legs, ths is really two phase. Look at vector diagrams for "delta" and "star" sometimes called "Y" to get a visual on it.

Have basically the same types of things on the aircraft. Gyro motors are 3 phase motors, but they'll run on 2 phases as long as you don't lose the common ground. Got an emergency inverter for a backup system. Takes DC and outputs 2 phases and a ground. I have a heck of a time trying to explain to the younger guys why the emergency inverter isn't designed to start the gyro motors (even though that's how the pilots check out the inverter and end up burning them up occassionally), it's only designed to keep them running in the event of a power failure.
About the 1 vs. 2 vs. 3 phase thing...I get that too. A lot of people seem to think they've got 3 phase power because they've got 220 hooked up to a dryer. I let them think that 'cause you just can't explain things to people who won't listen.

1- Because of the multiple shorted circuits a large current is produced on the rotor, giving a large magnetic flux. This causing the iron between the copper to become a magnet.
2- If an iron bar is placed in a magnetic field it will take on the prperties of the magnet with one end being "N" and the other being "S". If the maget is rotated the iron bar will rotate too. The large current between the iron bars on the rotor act as a shield so each piece of iron has properties independant of the other.

Ok, so it sounds like I really do need some magnetic material between my copper wire on the rotor. I've got an idea of stamping out some recetangles from an old car hood I've got laying around, epoxying a bunch of layers together, enough to make the thickness of the 20ga wire on the rotor, or more to make the air gap even tighter, and then mounting that mess to the rotor somehow. Maybe screw it down, or tape it up with some heavy duty plastic tape.

Single and two phase motors need an extra winding to start to "throw things out of phase" and some times to keep things out of phase. ( built in phase converters ) Start caps and run caps are sometime hooked here.

Shaded pole and that sort of thing?

I hope I am not making this more confusing.

I'm all about getting confused...as long as I get this thing spinning soon!

[mackrackit]

A couple of extra windings or something on the end, just enough to give it a bit of a kick?

Yep, that is why synchronous motors do not have good starting torque.

Have basically the same types of things on the aircraft. Gyro motors are 3 phase motors, but they'll run on 2 phases as long as you don't lose the common ground. Got an emergency inverter for a backup system. Takes DC and outputs 2 phases and a ground. I have a heck of a time trying to explain to the younger guys why the emergency inverter isn't designed to start the gyro motors (even though that's how the pilots check out the inverter and end up burning them up occassionally), it's only designed to keep them running in the event of a power failure.
About the 1 vs. 2 vs. 3 phase thing...I get that too. A lot of people seem to think they've got 3 phase power because they've got 220 hooked up to a dryer. I let them think that 'cause you just can't explain things to people who won't listen.

I do not bring the 2 phase thing up often. You should see the look on an inpectors face when I label a sub panel "2 PHASE".

Ok, so it sounds like I really do need some magnetic material between my copper wire on the rotor. I've got an idea of stamping out some recetangles from an old car hood I've got laying around, epoxying a bunch of layers together, enough to make the thickness of the 20ga wire on the rotor, or more to make the air gap even tighter, and then mounting that mess to the rotor somehow. Maybe screw it down, or tape it up with some heavy duty plastic tape.

Might be able to use welding rod. Laminates are used in transformers to suppress eddy currents, in small motors for cost. Large motors are cast iron/steel with a second pour for the aluminun. Air gap should be the same for magnetic and non magnetic parts. Sounds like you have punch press, How about a lathe? To attach things for testing, J B Weld.

Shaded pole and that sort of thing?

Yes, again that is why the rated HP is low on these motors. Back to top^.

I'm all about getting confused...as long as I get this thing spinning soon!

Can you imagine the spinning in Tesla's head. He reportedly modeled this all in his head.

[skimask]

Yep, that is why synchronous motors do not have good starting torque.

Then how do they get those AC types to work in electric cars (the ones with AC motors anyways) and the like?

I do not bring the 2 phase thing up often. You should see the look on an inpectors face when I label a sub panel "2 PHASE".

I checked the wiring at my house awhile back on a 'scope. I've got 2 legs of 120VAC, both in sync with each other, not 180 or 60 or 120 out of phase. What's up with that?

Might be able to use welding rod. Laminates are used in transformers to suppress eddy currents, in small motors for cost. Large motors are cast iron/steel with a second pour for the aluminun. Air gap should be the same for magnetic and non magnetic parts. Sounds like you have punch press, How about a lathe? To attach things for testing, J B Weld.

No lathe, no punch press, just access to a foot shear and a decent ruler, should be able to punch out a pile of decent rectangles in short amount of time. I wasn't going to use JBWeld, just whatever epoxy I could find that would work reasonably well on sheet metal. If that doesn't work, I'll pop-rivet the parts together. If I had a plasma cutter, I'd cut out chunks of frame rail and use that instead of the stacked up rectangles.
I don't have any welding rod handy, and I've got all this old scrap auto sheet metal laying around.

Can you imagine the spinning in Tesla's head. He reportedly modeled this all in his head.

I have trouble enough with 2 dimensions, let alone more than 3...by that I mean trying to imagine the interaction between voltage, current, and magnetic lines of flux...all at the same time...

Do ya think it matters much that I'm driving the thing using square waves vs. a halfway decent sine wave?