Effect of Step Skewing on the Cogging Torque of Permanent Magnet Synchronous Generator

Permanent Magnet Synchronous Generator (PMSG) is a generator whose magnetic field is generated by a permanent magnet located on the rotor and which does not require any external excitation source to generate the magnetic field. Although permanent magnet machines are high performance electric machines, there is a torque component that affects their output performance, being called cogging torque. Cogging torque also creates torque ripple during operation which also causes other disadvantages such as reduced efficiency, noise, and vibration in the system. To overcome the cogging problem, this research offers a step-skewing method. The purpose is to reduce the value of the change in reluctance with respect to position. A change in the axial dimension design of the rotor will reduce the value of the change in reluctance in the circumferential direction and thus the cogging torque will be reduced. The effect of the step-skewing in reducing the cogging torque on a permanent magnet synchronous generator is to be examined using 3D simulation using finite-element method (FEM) based software. Step skewing method is applied by varying the magnetic segments (j) parameter into 3, 4, 5, 6, and 7. The results show that the step-skewing method is effective in reducing the cogging torque on the permanent magnet synchronous generator. The greater the number of magnetic segments (j), the smaller the cogging torque value.