Analysis of Direct-On-Line Synchronous Reluctance Machine Start-Up Using a Magnetic Field Decomposition

Direct-on-line synchronous reluctance machines combine the characteristics of induction machines and synchronous reluctance machines. Saturation of core materials, the eddy currents, and the asymmetry of the rotor core and cage make it difficult to predict which kind of loads a machine can synchronize. In this paper, the start-up of a direct-on-line synchronous reluctance machine is analyzed with a magnetic field decomposition that makes it possible to quantify and isolate forces between any two distinct parts of an electric machine using a transient time-stepping finite element field solution. The results show explicitly which portion of the torque is produced by the rotor core and which by the rotor cage. Compared with conventional average torque analyses (also known as pseudo-constant-speed or quasi-steady-state analyses) used to distinguish between the torque on the rotor core and cage, the proposed method makes no assumptions on the state of the machine. This results in a more detailed view of the starting transient.