Analysis of the Cogging Torque Reduction in Permanent Magnet Generators for a Very Low Wind Speed

Abstract

This research examines the magnet structure’s effect on the performance of permanent magnet generators. The permanent magnet generator’s cogging torque (CT) is one of the characteristics that this article examines. In an electrical machine or permanent magnet generator, CT is a characteristic that can cause unwanted phenomena like vibration and noise. The permanent magnet generator’s magnetic flux density in the core is another crucial factor affecting the machine’s efficiency. The present study introduces this parameter. This study used the finite element method for magnetics to investigate and compare the values of the tangential and normal magnetic flux densities in air gaps. Using the magnet edge slotting technique might decrease the magnetic flux density, the total magnetic flux pouring into the air gap of the permanent magnet generator, and the CT reduction. It is demonstrated that using the two processes of slotting at the magnet edge can result in improved permanent magnet generator performance. The numerical calculation software FEMM 4.2, based on the finite element method, it was used to validate the CT of the permanent magnet generators under examination. It was discovered that the cogging torque of the proposed permanent magnet generator can be significantly increased—by about 99.3%—compared to the original design of the permanent magnet generators being studied. To retrieve the power that was lost when the magnet was cut, the authors improved the convex shape next to the rotor core. This made the magnet volume bigger, similar to the magnet design in the baseline model. The cogging torque was evaluated using FEMM and contrasted with the cogging torque of the baseline model. It was determined that the cogging torque diminished by 99.2% relative to that of the baseline model. This result is marginally lower than the reduction in the cogging torque value observed without employing convex magnets, which stands at 99.3%.