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In this article, the design and characteristic research of the coaxial magnetic gear for the contra-rotating propeller in the premium yacht are presented. The scale-down model of 1/25 is reviewed as the research of the applicability of the coaxial magnetic gear. The space harmonic characteristics of the magnetic field in the coaxial magnetic gear with the low gear ratio from 1 to 2 are investigated, and the optimized models with the surface-mounted permanent magnet and quasi-Halbach array are obtained using the response surface method. In the several operating points of the diesel engine, the magnetic loss and the resultant thermal characteristics are analyzed and compared in each model. Finally, the desired coaxial magnetic for the contra-rotating propeller in the premium yacht is achieved. [ABSTRACT FROM AUTHOR]

Axial‐flux permanent magnet synchronous machines (AF‐PMSM) using printed circuit board (PCB) windings are attracting interest because of an increased demand for machines with thinner geometries. A critical element in designing these machines is the choice of its PCB winding which should ensure high‐performance characteristics with an efficient use of the PCB surface. However, there is a gap in the knowledge regarding the performance of different PCB topologies. The research reported here is motivated by the need to compare common wave‐type PCB windings stator topologies. Accordingly, overlapping parallel wave, non‐overlapping radial wave and overlapping radial wave PCB winding topologies are assessed, using finite‐element analysis, and compared based on their key performance characteristics such as the generated back‐electromotive forces, inductances and electromagnetic torque. The PCB winding that provides the best torque production is then chosen and manufactured. Experimental tests on the prototyped PCB AF‐PMSM provide validation. [ABSTRACT FROM AUTHOR]

This paper investigates the characteristics of the radial force density according to the shapes of the flux modulation poles (FMP) in a surface-mounted vernier machine (SPMVM). The air-gap flux density harmonics obtained from the finite-element analysis method are analyzed using the analytical equations derived from the magnetomotive force and the air-gap permeance distributions. Then, in order to find the radial force density harmonics that generate the exciting force on the stator, the spatial orders and the angular frequencies of the radial force density harmonics are calculated by using the Maxwell stress tensor method. The analysis results show that the permeance harmonics generate the radial force density harmonics, but the resulting harmonics of the radial force density are time-invariant in the spatial domain. Consequently, the variation of the FMP shape can improve the torque characteristics of the SPMVM without the increase of the exciting force on the stator core. [ABSTRACT FROM AUTHOR]

This paper presents an accurate initial pole position (IPP) estimation method for a surface mounted permanent magnet synchronous motor (PMSM) without the use of pole sensors. To estimate the IPP, the proposed method uses the concept of reference frame. In this method, three torque commands, separated by 45° electrically from each other, are applied to the PMSM. Using the reference torque commands, moving distances are measured and transformation matrix is applied to eliminate the load torque term. Finally, the IPP is determined using the secant method. The IPPs under no load and at specific loaded condition are measured. The result of the load condition is compared with the previously proposed two reference frame method. The proposed method gives better result under load condition, compared with the two reference frame method, which fails to give satisfactory result under load condition. [ABSTRACT FROM AUTHOR]

The magnetic geared motor, which has improved torque density because of the magnetic gearing effect, has been researched. However, its narrow operating region due to the operating mechanism by the magnetic gearing effect and field flux by the PM is a challenge that needs to be overcome. Whereas, the doubly fed magnetic geared motor (DFMGM) can extend the operating region because of the double stator and double winding structure with the individual frequency control of the current fed to the inner and outer windings. However, two rotating magnetic fields, which are produced by the inner and outer winding flux, exist at the air-gap, and the large numbers of space harmonic components of the modulated flux density are produced at the air-gaps. These space harmonic components, which are produced by the winding MMF, influence not only the back-EMF of the winding but also the performances of the operating torque. Besides, the inner and outer windings affect each other in the back-EMF, and its characteristics appears differently in the inner and outer windings. Thus, in this paper, the structure, operating strategy, and basic characteristics according to the frequency condition in the inner and outer windings are presented. [ABSTRACT FROM AUTHOR]

• Proposed operation needs to ensure a high torque (>1 KNm) magnetic coupling. • A radial flux-CPMC (RF-CPMC) with magnet retaining rings and a flux concentrating-CPMC (FC-CPMC) are compared. • The electromagnetic and electromechanical characteristics are used for comparison. • Based on the installation environment and the magnet use, RF-CPMC is prototyped and tested. This paper presents design and comparative study of high torque coaxial permanent magnet couplings (CPMC) for the use in a tidal current generation (TCG) system. Two different models such as a radial flux-CPMC (RF-CPMC) with magnet retaining rings and a flux concentrating-CPMC (FC-CPMC) with inner and outer rotor yoke changed by retaining rings are analyzed to find the best model under certain design constraint conditions to achieve a minimum pull-out torque of 1.0 kNm. Moreover, the effect of the electromechanical characteristics such as the radial force, stress and deformation are analyzed for both models. Based on the analysis it is found that both RF-CPMC and FC-CPMC are capable of producing the pull-out torque higher than 1.0 kNm, however considering the installation environment and the magnet use, RF-CPMC is selected for prototyping, which is tested using a 3 MW induction motor based dynamometer system to compare its torque production capability with respect to the simulated model. The comparison shows that the prototype is capable of producing the required amount of pull-out torque. [ABSTRACT FROM AUTHOR]