Impact Of Inductance Parameters On Torque Of Interior Permanent Magnet Synchronous Motor

Interior Permanent Magnet Synchronous Motor(IPMSM) is capable of simplestructure, good reliability, high efficiency and high power density, with thesecharacteristics it has been widely used in traction applications, air-conditioning drive,ship and aerospace in recent years. IPMSM has high complexity of rotor magneticcircuit structure,and a non-linear characteristic due to saturations and cross-couplingimpact, so the inductance parameters are difficult to calculate accurately, so does theanalysis of the motor performance.First, the paper introduces the fundamental theory of permanent magnet motor andFinite Element Method. And based on these theories, a IPMSM model with lateralmagnet is established by the JMAG-designer software. After analysis of the magneticfield of the IPMSM model, flux linkage equation and torque equation are put forwardwhich contain cross-coupling impact between direct-axis and quadrature-axis. On thebasis of FE model of IPMSM, this paper uses frozen permeabilities method （FPM）tocalculate inductance parameters, and makes a theoretical analysis to the results of thecalculation. The results indicates that there is significant cross-coupling impact betweend-q axes, especially in the unsaturated region.Second，the impact of inductance parameters on max torque per ampere isanalyzed, the result reveals that when IPMSM is operated with high torque, thenegative increase of the reluctance torque caused by cross-coupling impact is animportant reason for the decrease of max torque per ampere.At last，the impact of width of stator teeth，width of magnet bridge，and the shapeof permanent magnets on magnetic field, inductance parameter and electromagnetictorque are analyzed. Then, a modified V-shape model is created, the comparison oftorque between modified V-shape model and lateral magnet model is made. The resultreveals that when the IPMSM is operated with high torque, the modified V-shape modelcan produce more permanent torque, meanwhile,it reduces the range of the negativeincrease of the reluctance torque cross-coupling. As a result, the modified V-shapemodel can produce more electromagnetic torque.