In this paper, we present improved Lumped-Parameter Models for simulation of a Interior Permanent Magnet Synchronous (IPMS) machine to calculate PM flux linkage, and Q and D-axis inductances which can be used for torque calculation. These improved models include all details of flux barriers and air bridges of rotor and also the effect of saturation in central posts and stator core. To validate the accuracy of these models, results are compared with the Finite Element Method results for a presented IPMS machine.