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Extensive literature has been produced on the investigation of eddy current losses in Surface-mounted Permanent Magnet (SPM) electric machines in presence of circumferential segmentation by analytical solution of two-dimensional (2D) models. What is missing in the present literature and constitutes the aim of this paper is a simple but accurate procedure enabling the designer to quickly and easily estimate the impact of circumferential segmentation on permanent-magnet loss reduction. The problem is hereinafter addressed in two stages: first the Helmholtz equation is solved in the permanent magnet region neglecting segmentation; then suitable gauge fixing terms are added to the vector potential and eddy current field solutions to account for segmentation. Unlike existing approaches, the method leads to manageable formulas whose accuracy is extensively assessed against finite element simulations on an example SPM machine equipped with a fractional-slot concentrated winding. Furthermore, simple practical rules are derived and validated regarding the impact of magnet segmentation on permanent-magnet losses caused by air-gap magnetic field space harmonics of different orders.

To achieve modular integration of relativistic triaxial klystron amplifier (TKA) devices and reduce the energy consumption of the whole high-power microwave (HPM) system, a compact Ku-band TKA packaged with permanent magnets is proposed and investigated in this paper. By optimizing the electromagnetic structure and utilizing TEM mode energy coupling, the length of the uniform magnetic field area required for the Ku-band TKA is reduced from 32 cm to 19.6 cm, with a reduction rate of 39%. By utilizing the NdFeB-N50M mainly magnetized in the ${R}$ direction, a permanent magnet guiding system weighing 90 kg is proposed. Besides, the length of the uniform zone is 20 cm with a longitudinal magnetic field of 0.5 T. Verified by the PIC simulation software CHPIC, an HPM with power of 430 MW and frequency of 14.25 GHz is generated when the diode voltage, current, and the injected microwave power are 340 kV, 4.2 kA, and 15 kW, respectively. The phase jitter of the output microwave is controlled within ${\pm } 5{^\circ }$ , which is beneficial to the coherent power combination of modular integrated TKA devices

This paper presents the design and fabrication schemes of a magnetic system consisting of segmented permanent magnet (PM) blocks, back-iron and frame structures. Here, a frame structure aims to bind PM blocks and iron structure. Non-intuitive design of segmented PMs and back-iron are obtained using multi-material topology optimization formulation. Subsequently, a non-magnetic frame structure is designed through a post-processing procedure, which is proposed using the smoothed fields of optimized PM and back-iron densities. Final design results are converted into computer-aided design (CAD) models and fabricated using conventional or additive manufacturing techniques. Segmented PM blocks, and back-iron structures are processed using water-jet cutting and wire electrical discharge machining, respectively. A frame structure is fabricated by additive manufacturing using a multi-jet printing machine. Using the proposed schemes, two magnetic systems are successfully designed and fabricated, respectively, for maximizing the magnetic field inside a rectangular cavity, and maximizing the magnetic force generated with a C-core electromagnet.

A fully submersible permanent magnet synchronous machine (PMSM) is introduced in this paper. Underwater operation requires that the machine parts have to be resistant to corrosion, and the electrically conducting parts need to be properly insulated from water. The machine under study consists of a rotor-surface permanent magnet rotor, protected by a glass-fiber-reinforced plastic (GFRP) cover, and a fully stainless stator. The novelty of the machine is found in the design and special materials used in the manufacture. The stator core is made of ferritic stainless steel laminations, and the selected winding material is polyvinyl chloride (PVC) insulated copper wire. An extra low-speed, stainless-core submersible PMSM was constructed and tested. To simplify the machine construction, a tooth-coil single-layer winding was adopted. An asymmetric stator design was selected to enhance the machine performance. The performance of the 1.7 kW, 80 r/min machine was analyzed by finite element analysis (FEA) and validated by experimental tests, where despite a very low rotational speed, 74% efficiency was reached at the target load point. The PMSM was found to be fully functional for the application.

This paper proposes a novel analytical method for the analysis of the dynamics of electrical machines. The method is applied to the analysis of complex permanent magnet (PM)-type magnetic contactors (MCs), which exhibit strong magnetic non-linearities and a high portion of stray and leakage magnetic fluxes. The latter means that the analysis of PM-type MCs using traditional magnetic equivalent circuit (MEC) methods is impossible, thus requiring computationally expensive and time-consuming finite element analysis (FEA). To overcome the limitations of traditional MECs, the magnetic field distribution in PM-type MC is studied in great detail, and a novel non-linear dynamic MEC (ND-MEC) method is proposed. The accuracy of the ND-MEC method is comparable to that of FEA which is achieved by accounting for non-linear effects and dynamic changes in the magnetic flux distribution using a novel stray path elliptical function. Furthermore, the applicability of the ND-MEC is extended to the time domain by combining it with the time difference method (TDM). The complete method, referred to as the non-linear transient path energy method (NT-PEM), combines the ND-MEC, TDM, and a path energy method for the calculation of electromagnetic forces. The validity of the NT-PEM is verified by comparing it with 3D FEA and experimental results obtained from a PM-type MC prototype. The NT-PEM is a fast and inexpensive alternative to FEA, which is particularly advantageous when many designs must be analyzed and optimized while reducing analysis costs. The proposed method can also be applied to the analysis of emerging technologies dealing with multiphysics coupled problems, as in the case of smart materials.