I think the more relevant question is the component for the air gap MMF which is embodied in the total magnetizing current. If the air gap MMF is significantly greater than the magnetic material MMF then the return on investment for using higher permeability + high saturation flux density material may not be realized.If we assume the same geometry, is the air gap a constant rather than a variable?
- Same magnetic field in stator with different current flows.
- Same air gap.
- Same toque
So, with different current flows at the stator windings, we may have same torque.
Am I right? I mean no load case.
I think this is because there is no soft magnetic material which will satisfy the high permeability and high saturation magnetiztion. We don't know how to achieve that particular magnetic properties. We know what is the best material, but we do not know how to make it. And my question is if such materials are developed, what will be the merits of that materials in motor? Especially in terms of efficiency?I'd ask the question - why haven't induction machine manufacturers gone down that road already if the economics were justified.
Air gap, Hmmm, it's a difficult part for me to explain because I do not understand it clearly. Sorry, I am a mateirlas engineer!"I think the more relevant question is the component for the air gap MMF which is embodied in the total magnetizing current. If the air gap MMF is significantly greater than the magnetic material MMF then the return on investment for using higher permeability + high saturation flux density material may not be realized."
There's the root of the problem which must be resolved. Suppose 60% [or more] of the magnetizing current goes into driving the air gap flux - for the same air gap structure the pay-off for improving the magnetic material properties would not necessarily be significant.With high permeability materials, we can get the same magnetization value(say 1.5T) with less current. Therefore, we can save significant amount of copper loss.
My point is that the first step is magnetization of stator core.
Does it make sense?
Well I consider it very illustrative to start up a 700W hand drill having a weak grid supply. You will see lights do darker for a moment...jinksung, the way I understand this and was taught in school, the current in an induction motor at no load is almost completely reactive current, ie. almost 90 degrees out of phase. You're not paying for the electricity used in most cases since the utility company bills on in phase component. As the motor is loaded the in phase resistive component increases and so does your electrical bill. The two components of current add vectorily so that means the phase angle of the current will move in the direction of zero degrees as the motor is loaded. Another point to remember is the spinning rotor creates a back emf opposite to the line voltage which limits the current through the motor windings just to the point of overcoming the resistance to turn the rotor. As the motor is loaded the back emf is reduced which increases the current flowing in the windings. That will make the motor heat up and if loaded enough stall and burn out the windings.