Homebuilt handmade "3 phase" electric motor

[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?

[mackrackit]

The AC electric cars I have looked at use Async motors like the one you are building. Spped control is easy with a varibl frequency drive like the one you are building. Depends on how the motor is built as to the low rpm torque developed.

Synchronous motors with rotor windings to a controler can give good low rpm torque but then the overhead will increase, and more trouble with slip rings and all of that.

I knew I was going to confuse something. Your house like most I think have one transformer connected to one of the phases provided by the power company. The transformer has two output taps, both 120 volt. So both legs are on the same phase.

A typical 240 three phase will have one 240 leg and two 120 legs. ( some are 208/277 but that is another story) All coming from different transformers. Look at a power utility pole. If I place a meter across any to legs or phases it will read 240 volt. The water heater thing I mentioned is what messed this up .

The attached pict is a schematic of a water chiller. The compressor is 3 phase and the circulation pump is a standard 240 volt setup. The pump motor runs from two of the 3 phases making it a two phase motor. The same motor will also run on the 240 two leg single phase at your house.

But you can not feed a transformer with one phase and have three taps and run a 3 phase motor.

[mackrackit]

Hi Skimask,

Did you get your motor working?

[skimask]

Hi Skimask,
Did you get your motor working?

Not yet, kinda slowed progress on the motor, holidays and stuff (birthdays, parties, etc).
I've gotten it to kick quite a bit, but not go 'round and 'round...so that's probably a software issue.

[mackrackit]

Understaand all of that (family first).

Might be a time problem. Could you post your algorithm. Might be able to help.