Design and analysis of a novel claw-shaped modular stator relieving-DC-saturation doubly salient machine with 3D complementary magnetic circuit

Here, a novel DC-excited doubly salient machine with a claw-shaped modular stator and three-dimensional (3D) complementary magnetic circuit is proposed for wind power generation application. The key is to artificially construct a 3D complementary structure to suppress torque ripple and employ auxiliary slot-opening PMs to relieve DC-saturation in the stator core and improve overload capability. The novel 3D complementary structure provides an alternative magnetic path for the main flux, so the flux leakages in the air gap at open-circuit position are effectively cancelled, and the flux in the yoke remains relatively constant. Hence, the output torque ripple is suppressed. Furthermore, the saturation issue in the stator is solved with auxiliary permanent magnets which have opposite magnetization direction to that of DC field excitation. Therefore, the torque capacity of the machine is improved. Here, the machine structure and operation principle are introduced, and a 2D equivalent model is also developed to replace the 3D model to improve the calculation efficiency. Multi-objective optimization algorithm is developed to improve the performance of this new machine. The validity of machine design is finally verified with 2D and 3D finite element analysis.