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High-speed (HS) electrical machines provide high system efficiency, compact design, and low material consumption. Active Magnetic Bearings (AMBs) bring additional benefits to the high-speed system, such as elimination of the friction losses, reduced wear and maintenance, and a built-in monitoring system. High-speed drivetrains are usually designed for specific applications and require a high level of integration. This paper describes a design method of the HS electrical machine supported by AMBs, considering their mutual influence on the system performance. The optimization procedure, which takes into account both the electrical machine and bearing designs is developed. The optimization is based on a multiobjective genetic algorithm. The selected optimization parameters include the AMB and machine dimensions. The optimization objectives cover the electrical machine performance and the rotordynamics. The results of the proposed optimization algorithm are implemented in the constructed 350 kW, 15 000 rpm induction machine with a solid rotor supported by AMBs. The prototype tests verify the design and optimization results.

Permanent magnet materials are nowadays widely used in the electrical machine manufacturing industry. Eddy current loss models of permanent magnets used in electrical machines are frequently discussed in research papers. In magnetic steel materials we have, in addition to eddy current losses, hysteresis losses when AC or a rotating flux travels through the material.Should a similar phenomenon also be taken into account in calculating the losses of permanent magnets? Actually, every now and then authors seem to assume that some significant hysteresis losses are present in rotating machine PMs. This paper studies the mechanisms of possible hysteresis losses in PMs and their role in PMs when used in rotating electrical machines. Index Terms-Permanent magnet, permanent magnet material, permanent magnet losses, hysteresis, hysteresis in permanent magnets. I. INTRODUCTIONERMANENT magnet (PM) materials are widely used in electrical machines. The applications where permanent magnet machines are utilized include for example industrial machines, wind power generators, traction motors, linear machines, high-speed machinery, and machines used in aerospace applications [1]-[6].Eddy current loss models of PMs used in electrical machines are frequently discussed in research papers. Sintered PM materials have a significant macroscopic resistivity, in the range of 100-200 µΩcm, providing eddy currents with paths Manuscript

A high-speed squirrel-cage induction machine requires a totally different design compared to the traditional squirrel cage industrial motor because of the mechanical limitations caused by the high speed. This results in a more complicated rotor construction and expensive material selection, and sets higher standards for the manufacturing precision. The objective of this paper is to demonstrate the design aspects, material selection, and manufacturing of a squirrel cage rotor for high-speed applications. In this paper, the rotor dimensioning approach based on equations and data analysis is presented. Rotor material selection and construction topology influence on the electrical machine design are discussed. The results are illustrated with the design of a 6 kW, 120 000 rpm induction machine for a turbo-circulator. The rotor parameters' influence on the electromagnetic performance of the designed machine is demonstrated. Mechanical stresses for different topologies are studied with Finite Element Method (FEM) analysis. Several manufacturing methods for producing a high precision rotor are described and compared. The presented rotor design approach, which enables high electromagnetic performance and robust construction, is verified by the testing of a prototype.

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