Evolution of requirements to the material properties of permanent magnets for electrical machines

The paper presents the development of a technology for the production of magnetically hard alloys intended for use in the inductors of electrical machines. It shows how the properties of such alloys affect the design of electrical machines. The paper further describes the application-determining properties of the most common alloys. It also proves why it is necessary to control the excitation flux in traction motors. In addition, the paper describes the fundamental possibility to use hysteresis motors for traction due to their ability to control the excitation flux using the stator circuit. It further analyzes the advantages and disadvantages of such motors. Consideration is given to hysteresis motor control algorithms that improve its energy performance when starting and running. The paper also compares the magnetic reversal of the inductor in hysteresis motors and in permanent-magnet motors while discussing the magnetic reversal of hysteresis motor rotors in electric drives in detail. As a result, the paper concludes with the requirements to alloys to be used in the inductors of traction hysteresis motors.