A study on oscillatory and effective torques of an line-start PM motor in start-up operation

摘要

In this paper, various effective and oscillatory torque components in a line-start permanent magnet (LSPM) motor are analyzed using the principle of superposition through the analytic approach with an equivalent circuit. According to the independent sources, in the asynchronous speed the induced rotor current and braking stator current are derived by using the DQ equivalent circuit and Laplace transformation. Then, two effective components and three oscillatory components of torque are calculated quantitatively by using the analytic torque equations. Finally, to check usefulness of the proposed method, the current and torque characteristics are compared with finite element analysis and measurement results for various speeds.