Analysis of Frequency Characteristic of Surface Permanent Magnet Synchronous Machine

The surface permanent magnet synchronous machines have been widely used in direct-drive wind power generation system. The transient reactance and time constants are important parameters to describe electric transient process, and determine the safe operation and stability of the system. First, an analytical method is presented to predict the direct- and quadrature-axis operational inductances originating from asynchronous test method. The finite element results validate the analytical prediction. Next, the physical nature of the transient process is concluded according to the mechanisms of eddy current field. Finally, based on the frequency characteristic of operational inductance, the subtransient inductance and time constants of the surface permanent magnet machine can be obtained by curve fitting.