In this paper, a new topology of fractional slot concentrated winding double rotor axial flux permanent magnet synchronous motor (FSCW-DRAFPMSM) is introduced. The desired structure consists of a nonslotted stator core and two rotor discs. The pole number of the two rotors is different and these two rotors rotate at different speeds in opposite directions. A sample motor with an output power of 200 Watts is designed with the proposed structure. The two rotors of this sample motor rotate with speeds of 1200 and 857 rpm. The Finite Element Method (FEM) is employed to evaluate the performance of the proposed structure. Some performance characteristics of the case study machine, such as the Back EMF, input power, and electromagnetic torques of two rotors are presented to confirm the correctness of the operation of the proposed structure. In addition, the shifting technique is used to improve the Back EMF waveform of the machine. An analytical formula is proposed for calculating the fundamental component of the Back EMF waveform. The accuracy of the formula is approved by FEM.

This paper presents a new algorithm for sizing equations of an Axial Flux Permanent Magnet (AFPM) machine based on an analytical method. To obtain a better performance, the dimensions of the stator and rotor cores are calculated. It is shown that the magnetic flux densities throughout these cores remain closed to the flux density of the B-H curve knee point of the ferromagnetic material characteristics. A new algorithm is proposed to determine the dimensions of the different parts of the machine, and it is used to calculate the height of the permanent magnet precisely. To show the effectiveness of the suggested algorithm, a sample AFPM machine is designed based on sizing equations, and Finite Element Analysis (FEA) is employed to validate these design formulas. A complete simulation study is accomplished, and some of the results are presented to confirm the accuracy of the sizing equations.

Mitigating the cogging torque is an important issue in designing the YASA machines. The main aim of the paper is to optimize an efficient technique to mitigate the cogging torque of YASA machines. In the suggested technique, the permanent magnets (PMs) are segmented into several segments in the radial direction, and then these PM segments are shifted at appropriate angles in the peripheral direction. The proposed PM segmentation method is compared with the conventional PM segmentation as well as the conventional PM skewing approaches in terms of the amount of cogging torque reduction and the amount of negative impact on the generator load-ability. It is shown that compared to the other two studied approaches, the proposed method is more effective in reducing cogging torque and at the same time, has a less negative impact on the generator output power. Using the suggested technique and via several finite elements based simulations, it is shown that without causing a significant negative impact on the generator load-ability, the generator cogging torque can be reduced considerably (about 90%). By implementing the RSM (Response Surface Methodology), optimal shift angles of the PM segments (factors) are determined to mitigate the cogging torque and maintain the generator load-ability. The experiments are carried out based on the RSM, as an important topic in the statistical DOE (Design of Experiments) approach, to study the impacts of PM segments shift angles on the output power and cogging torque of the YASA-AFPM generator. All of the experimental samples are extracted via the FEA simulations. Also, some of the simulation results are verified using the experimental tests.