II. SYSTEM DESCRIPTION The following assumptions are made for the AC asynchronous motor in this paper:1) The magnetomotive force is sinusoidal distributed along the air gap; 2) Ignore the magnetic saturation; 3) The self-inductance and mutual inductance of each winding are constant; 4) Ignore the core loss. After the synchronous rotation coordinate transformation and rotor flux orientation, the model of AC asynchronous motor in m t- coordinate system can be written as