Modeling, Simulation and Performance Evaluation of Cage Rotor Permanent Magnet Motor Fed by Variable Speed Drive

With increasing demand for higher efficiency, engineers are looking for an alternative solution to replace induction motors (IMs) in many applications. One of the very promising topologies is the permanent magnet (PM) motor with a squirrel cage on the rotor, which is referred to as the cage rotor PM motor in this paper. Based on the literature survey, the cage rotor PM motors have been studied and compared to IMs for direct on-line applications. Some studies also investigated the performance of line start PM motors (LSPMs) using a conventional VSD by comparing it to an IM using the same VSD. The comparative evaluation shows that, in most operating conditions, the LSPM drive provides better performance (usually higher efficiency) than the IM drive. In this paper, a d-q dynamic analytical model of the cage rotor PM motor is derived. The model is intended to be used in place of finite element analysis (FEA) and for purposes of control development. The model is implemented in Matlab/Simulink and used to study the behavior of different types of the cage rotor PM motor; line-start PM and light cage PM motors, when fed by a standard, scalar controlled drive. The analytical results are verified against the FEA, which shows excellent agreement.