Abstarct: Hysteresis motors are among the main selections for some special high speed applications, e.g. centrifuges, gyroscopes, and turbochargers, because of their unique features. The operation mechanism of these motors is baxsed on the magnetic hysteresis phenomenon. Unfortunately, due to the complexities of accurate hysteresis models, as well as their coupling the modern modeling techniques of electric machines, approximate methods have been used in most of the previous researches on the hysteresis motors. In this dissertation, the capabilities of multi-stack structures of disk-type hysteresis motors are investigated. Stators with slotless magnetic core and without magnetic core have been proposed to be employed in these structures, in order to reduce the parasitic losses. An algorithm is presented for design optimization of the studied motors, in which the shortcomings of previous works have been resolved. A novel approach has been introduced for the indirect coupling of classical Preisach model and finite element model of the studied motors. This approach is baxsed on the linear approximation of the hysteresis characteristic for each point of the hysteresis disk, between two successive time instants. To find the accurate field distribution inside the hysteresis disk, a separate Preisach block has been considered for each spatial field component of each element in the rotor mesh. The finite element model has been replaced by a new integral model of the studied motors, in order to reduce the calculations time, and hence, another modeling method has been proposed for these motors. It is shown that the new method is very accurate and it is much faster than the first method. An important result of these modelings is that the parasitic losses are negligible for the studied structures. The proposed procedures for design optimization and modeling of the motors have been verified by the experimental results obtained from a prototyped sample motor. Capabilities and limitations of the slotless and coreless motors have been compared. Furthermore, through a systematic experimental method, studied structures have been compared on the basis of some important criteria. The most important result of these comparisons is that the circumferential flux path in hysteresis disks is superir to the axial flux path.