Analysis of the Impact of Magnetic Materials on Cogging Torque in Brushless DC Motor

The cogging torque is the most significant issue in permanent magnet applications, since it has a negative impact on machine performance. In this article, the impact of magnetic materials on cogging torque is analyzed on brushless DC motors (BLDC). The effect of neodymium magnets (NdFeB), compression molded magnet, and samarium cobalt (SmCo) magnet on the cogging torque is analyzed to the BLDC motor designed for hybrid electric vehicle traction that has the peak power rating of 50 kW motor with 48 stator slots and 8 rotor poles. With the presence of these three magnetic materials, the cogging torque is estimated independently using multiposition simulation. The multiposition is simulated using a transient application that runs at constant speed. The results of cogging torque, rotational speed, angular position of BLDC motor, and magnetic flux density distribution have been presented. Also, the maximal, mean, minimal, rectified mean, and rms values of cogging torque were provided.

Stator flux barriers to improving interior permanent magnet motor characteristics

There are many methods to improve the characteristics of permanent magnet motors. One of them is by making flux barriers on the stator or rotor, or both. This paper discusses the adding stator flux barriers on the rectangular-shaped stator of the interior permanent magnet motor. The purpose is to increase the maximum rotation of the machine. The shape of the flux barrier is circular considering the ease of the manufacturing process, with the proposed diameter is one slot pitch. Several diameters of larger and smaller sizes will also be simulated for comparison. Other parameters, which are cogging torque and stator core loss, are also investigated. Design and simulation are carried out analytically and numerically using 2D finite element analysis. The simulation results indicate that the proposed flux barrier diameter can provide the maximum rotation with only a tiny decrease in output torque. In this regard, it can be concluded that the stator flux barriers affect the speed than output torque. Additional advantages are also obtained from the decrease in cogging torque and core loss at the base speed compared to a stator without flux barriers.

Design and Analysis of a Permanent Magnet Vernier Machine with Non-Uniform Tooth Distribution

To improve the torque performance of the permanent magnet vernier machine in the direct-drive system for Unmanned Aerial Vehicle (UAV), this paper proposes the topology of non-uniform tooth distribution. This distribution, considering the additional flux harmonics, aims to contribute to torque improvement, whereas the cogging torque also increases at the same time. A phasors method is proposed to solve the issue caused by the non-uniform structure, adjusting the mechanic angle of each tooth reasonably to restrict the cogging torque. In addition, the non-uniform design is illustrated in detail, which includes the method of grouping the teeth, considering the factors of series pole ratio and winding layout. By using the three-dimensional finite element method, torque is significantly increased without additional torque ripple, which satisfies the desired design target.

Automatic Tolerance Analysis of Permanent Magnet Machines with Encapsuled FEM Models Using Digital-Twin-Distiller

Tolerance analysis is crucial in every manufacturing process, such as electrical machine design, because tight tolerances lead to high manufacturing costs. A FEM-based solution of the tolerance analysis of an electrical machine can easily lead to a computationally expensive problem. Many papers have proposed the design of experiments, surrogate-model-based methodologies, to reduce the computational demand of this problem. However, these papers did not focus on the information loss and the limitations of the applied methodologies. Regardless, the absolute value of the calculated tolerance and the numerical error of the applied numerical methods can be in the same order of magnitude. In this paper, the tolerance and the sensitivity of BLDC machines’ cogging torque are analysed using different methodologies. The results show that the manufacturing tolerances can have a significant effect on the calculated parameters, and that the mean value of the calculated cogging torque increases. The design of the experiment-based methodologies significantly reduced the calculation time, and shows that the encapsulated FEM model can be invoked from an external system-level optimization to examine the design from different aspects.

Optimal Design of Step-Sloping Notches for Cogging Torque Minimization of Single-Phase BLDC Motors

This paper presents a method for reducing the cogging torque for a sloping notch with two notches applied on the stator teeth. The accuracy of FEA was confirmed by a comparison with a previous model using an asymmetric notch for the experiment data and 3D FEA results, followed by a comparison of the cogging torque of a two notches model and a sloping notch model. The sloping notch model was modified to a step-sloping notch model in consideration of a potential manufacturing process. The optimal design for minimizing the cogging torque was developed considering the sloping degree, angle, position, and size of the notches. As the optimal design result, the cogging torque on the optimal model was reduced. Finally, the analysis and optimal design results were confirmed by FEA.