Different from the design of conventional permanent magnet (PM) motors, high-speed motors are primarily limited by rotor unbalanced radial forces, rotor power losses, and rotor mechanical strength. This paper aimed to propose a suitable PM motor with consideration of these design issues. First, the rotor radial force is minimized based on the selection of stator tooth numbers and windings. By designing a stator with even slots, the rotor radial force can be canceled, leading to better rotor strength at high speed. Second, rotor power losses proportional to rotor frequency are increased as motor speed increases. A two-dimensional sensitivity analysis is used to improve these losses. In addition, the rotor sleeve loss can be minimized to less than 8.3% of the total losses using slotless windings. Third, the trapezoidal drive can cause more than a 33% magnet loss due to additional armature flux harmonics. This drive reflected loss is also mitigated with slotless windings. In this paper, six PM motors with different tooth numbers, stator cores, and winding layouts are compared. All the design methods are verified based on nonlinear finite element analysis (FEA).

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This paper is aimed to provide the detailed design and operational investigations of synchronous reluctance motors (SynRM) that are commonly assembled by laminated electromagnetic steels. The magnetic flux paths in the SynRM rotors with various barrier and segment compositions will be analyzed, along with the generated motor torque and loss assessments. As the related mechanical cutting and/or punching processes on the rotor steels are required to achieve desired direct-and quadrature-axis reluctance ratios, their impacts to the flux paths due to saturations will also be thoroughly evaluated. Assisted by three-dimensional finite element analyses, the results clearly indicated that the additional annealing process on the electromagnetic steel strips must be introduced for these SynRM designs with smaller sizes and higher efficiency requirements.

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A new aromatic diamine, with an isopropylidene and bromo-substituted arylene ether structure, 3,3Ј,5,5Ј-tetrabromo-2,2-bis[4-(4-aminophenoxy)phenyl]propane, was synthesized by the nucleophilic substitution reaction of p-chloronitrobenzene with 3,3Ј,5,5Ј-tetrabromobisphenol A, followed by a catalytic reduction of the resulting dinitro compound. Novel aromatic polyimides with inherent viscosities ranging from 0.53 to 2.1 dL/g were then obtained by a one-step or two-step polymerization process with this diamine and various aromatic dianhydrides. These bromine-containing polyimides showed typical amorphous diffraction patterns and were readily soluble at room temperature in N-methyl-2-pyrrolidone, N,NЈ-dimethylformamide, N,NЈ-dimethylacetamide, and even in less polar solvents such as chloroform, tetrahydrofuran, and pyridine. They also dissolved in dimethyl sulfoxide, m-cresol, o-chlorophenol ,or concentrated sulfuric acid with heating. Glass-transition temperatures were 272-303°C, depending on the nature of the dianhydride moiety. Thermogravimetric analysis showed that all the polymers were thermally stable, with 10% weight loss occurring between 465 and 499°C in nitrogen and between 457 and 492°C under atmospheric conditions. The bulky bromine substituents not only increased the solubility but also compensated for the loss of thermal properties caused by the flexible ether linkage.