Calculation And Analysis Of Electromagnetic Field In Line-start PMSM

The permanent-magnet synchronous motor (PMSM) has the same operating principle as that of the electric excited synchronous motor. Because of adopting the permanent magnet to excite, the structure of the motor is greatly simplified and the manufacturing costs have been reduced to a certain extent, meanwhile the slip ring and the carbon brush are not used so that the working reliability of the motor has improved. With the absence of the exciting current losses, the power density and the efficiency have been increased correspondingly. Therefore more and more attention has been paid to the PMSM and they have been applied more and more widely in all fields in recent years.First of all, the purpose and the significance of studing the PMSM are introduced as well as the present development state home and abroad in the paper. The operating principle of the line-start PMSM and its design features are declarated briefly. Then the transient electromagnetic field of an 18.5-kW, 6-pole PMSM is calculated and analyzed using the time-stepping FEM coupled with field and circuits. The effects due to the variation of flux barrier of rare-eart size and type of winding- distribution on the starting torque, starting current and the starting counter electromotive force of the motor are studied and analyzed. Finally, the method of calculating the stator exciting current is proposed, by which the sinusoidal time-variation electromagnetic field of the prototype motor under work condition is solved. The validity of the mathematical model of the motor and the feasibility of the method applied to calculating the electromagnetic field of the line-start PMSM are verified by comparing the experimental results derived from the prototype motor with the calculated values. At the same time, the effects due to the variation of flux barrier of rare-eart size and the permanent-...