Magnetic gears are able to transmit torque between an input and an output shaft without mechanical contact. As for electrical drives, torque density, acoustic noise, and torque ripple are of primary concern. This paper describes the influence of the pole numbers on the radial forces and the cogging torques. We show how continuous and discrete skewing can suppress torque harmonics effectively. Further, we investigated different simulation modes for magnetic gears using finite-element software. A multiobjective optimization was conducted to find a Pareto-optimal magnetic gear, whose cogging torque was minimized by skewing one rotor. Finally, we present a prototype with a gear ratio of 1:21, and compare finite-element results with the measurements of unskewed and skewed magnetic gears.

This paper deals with the analysis and optimization of radial, coaxial magnetic gears. Multi-objective optimizations of the modulator shape of two magnetic gear configurations, one with and one without back iron on the outer rotor, are presented and discussed. The focus of this publication is to show that a magnetic gear with the same total volume and output torque can provide a much higher efficiency when the outer rotor is built with no back iron. To guarantee comparable results, equal start geometries, objectives, and appropriate optimization parameters are considered. After the optimization process, the geometries of the two gear configurations show different optimal modulator shapes and, therefore, different flux distributions. The gear configuration without back iron achieves a comparable torque capability in comparison with the gear configuration with iron yoke. However, 2-D finite elements calculations estimate for the latter design a loss reduction of 70%.

This work presents a tilt stabilization coil inside an exemplary high speed bearingless disk drive. The coil is based on the passive, electrodynamic ‘Null-Flux’ principle where there are no coil currents and, thus, no losses when the rotor is non-deflected during rotation. The proposed conductor structure is then used as a means of active actuation on the rotor by energizing the coil actively for first producing tilt torque. Modifying the structure geometrically into multiple, coaxial conductor loops which are energized with currents in the same or in equal direction then allows producing additional axial forces and tilt torque with multiple degrees of freedom, depending on the coil design. Different connection possibilities allow the combination of active and passive characteristics. Simulation and measurement at prototype drives demonstrate the functioning of both, the passive stabilization and the active actuation principles.

In this paper, a magnetic-geared motor with an integrated bearingless high-speed rotor is proposed. Active two-axis suspension forces are provided to the suspended high-speed rotor by three-phase suspension windings. The principles of magnetic suspension and torque generation are presented. In addition, the suspension characteristics are evaluated in 3-D finite element analysis. A test machine was built, and both magnetic suspension and rotation were verified. As a result, the principle of a magnetic-geared motor with a magnetically suspended bearingless high-speed rotor has been confirmed for the first time.

Passively magnetically stabilized degrees of freedom yield the benefit of reduced complexity and therefore costs. However, the application of passive magnetic bearings (PMBs) also features some drawbacks. The poor damping capability leads to exaggerated deflection amplitudes when passing the resonance speeds of the applied system. This results in the necessity of external damping. Complying with the goal of costs and complexity, viscoelastic materials offer a suitable solution. However, these materials show high frequency and temperature dependent properties which induce the necessity of a proper model. Thus, the design of systems, as presented in this paper, requires accurate modeling of the dynamic behavior including the nonlinear characteristic of damping elements to predict the system displacements. In the investigated setup only two degrees of freedom remain to be controlled actively. These are the axial rotation and the axial position of the rotor which are controlled by the motor and an active magnetic axial bearing (AMB). This article focuses on the rotor dynamic modeling of a radial passively magnetically stabilized system especially considering the nonlinear behavior of viscoelastic damping elements. Finally, the results from the analytic model are verified by measurements on a manufactures test system.

Position measurement is a major topic for the control of nearly every moving or rotating device. The demand for reliable and affordable position measurement systems is high. This paper presents the design of an eddy current position sensor and explains the working principle, which is based on injection locking of coupled oscillators. Thereby, the stability and the characteristic of the sensor are dependent on the combination of the used components. To investigate the complex dependency of the parameters, a single-axis sensor was analyzed by a coupled magnetic 2D finite element and an analog electronic simulation. To achieve a stable operation, a high linearity and a high sensitivity an optimization of the sensor was conducted. The suitability of the simulation results were verified by measurements on an implemented sensor.