In order to establish the mathematical model of synchronous motor, it is necessary to make necessary assumptions about the actual three-phase synchronous motor to simplify the analysis and calculation. It is generally believed that:

The magnetic permeability of (1) motor magnet is constant, ignoring the influence of hysteresis and magnetic saturation, eddy current and skin effect.

(2) For the longitudinal axis and the transverse axis, the motor rotor is completely symmetrical in structure.

(3) The position difference of the three windings of the stator is 120? From an electrical point of view, the three windings are identical in structure. At the same time, they all produce sinusoidal magnetomotive force in the air gap.

(4) The slots and ventilation ditches of the stator and rotor do not affect the inductance of the stator and rotor of the motor, that is, the surface of the stator and rotor of the motor is smooth.