Originally Posted by sikeston34m
No, it's not magnetized at all really.
I've seen this in the forklift AC motors at work. This is also something that throws a monkey wrench into the gears of my understanding.
I realize these are sensor based motors, but I've always wondered a few things:
#1. How does the stator conduct magnetism in such a way to get rotation? I'm sure it's in the winding. Please point me toward more information on this.
This is the beauty of an Induction motor, unlike permanent magnet type, series wound type, or other synchronous type motors, the AC inductions stator coils (stationary) have a 3 phase AC power going through them. Now there are three seperate phases in the motor which are each connected to the ends of the next one (just imagine three people holding hands in a circle), and there are also 6 poles, which if you know anything about Brushless DC motors, you times the poles by the phases... 3 phase x 6 poles = 18 coils, each phase consisting of 6 coils in series, get it? Now, imagine each AC power wave being 60 degrees out of phase to the next one, and then imagine that each coils magnetic field expanding with the AC signal, then from the starting point of the first 'sine' wave (let's call it Phase 1), 60 degrees later the phase 2 starts, then some 60 degrees later the phase 3 coil is starting it's way up. At the time the Phase 1 coil has hit zero again 60 degrees later, it goes into 60 degrees negative wave, and so on, and so on. Now try to imagine all this going on in a circular plane, there being somewhat smooth transitions between each Phase coil to the next... what do you have? A seemingly full rotating magnetic field; imagine having magnets around the perimeter of a motor case and making them spin, spinning field right, well here you are doing it with AC magnetic fields. Invented by the magnificent Nikola Tesla over 100 years ago, some think he was an alien brought here because he invented the 20th century, way ahead of his time.
Anyways part two, the rotor...
Okay, this is super simple really, have you ever had a Neodymium magnet and held it close to alum. or copper plate? Well, nothing happens right? Well as soon as you start to move it, there is resistance, the faster you move it, the more resistance that is apparent. That's because for every action there is an opposite, but equal REACTION (well with magnets it's not quite equal), the MOVING magnetic field in the magnet is INDUCING a magnetic field INTO the very material you are moving it along, the magnetic field induced will naturally be OPPOSITE that of the magnet pole facing it. When you stop moving it, it disappears, when you go, it repels, get it? It's an active dynamic relationship.
NOW, imagine that rotating magnetic field I explained, the rotor is not more than a hunk of aluminum, well aluminum bars actually under that sheathing... anyways, the rotating magnetic field going on around it is INDUCING (hence Induction motor) a magnetic field into the rotor which will be opposite the fields and repel, yada, yada... now to control the speed of the motor, you have a variable frequency controller (inverter), electric car inverters can do 0 - 400 Hz operation, the higher the frequency, the faster the rotating magnetic field is spinning, and the faster the field is spinning, the motor magnetic 'slip' it's called is placed on the rotor, which creates more repulsion, and thus more torque, and power.
My fingers hurt, I think I touched on the basics, err, fundamentals of how it works.
BTW, the rotor weights 34lbs, pretty light really considering how much weight it will be moving!
#2. Can these be used in a sensorless setup? Do they Generate enough EMF to go sensorless?
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