Asymmetries in Planetary Touch-Down Bearings

For certain applications, magnetic bearings are preferred over rolling element bearings, for example, due to the absence of mechanical friction leading to high efficiency and low maintenance needs. However, they also require touchdown bearings (TDB) to bear thpe rotor in case of a malfunction or overload. For vertical systems with high DN numbers, like outer rotor flywheels, the design of the TDB becomes a challenging task. For such systems, the planetary TDB can be applied. The suitability of this design has already been shown in the literature (Quurck et al., 2017; Quurck et al., 2018). However, there are multiple parameters influencing the performance of the planetary TDB. For example, if an asymmetric planetary TDB should be preferred over a symmetric one, and if this is the case which asymmetries increase the performance of the planetary TDB. Therefore, this paper investigates asymmetries in planetary TDB in a simulation study performed with the Matlab-based simulation environment ANEAS. The results of this study indicate that the performance of planetary TDB can be increased when the air gap of the individual bearing units differs. If the air gap from one bearing unit is reduced by 20 % the maximum force acting on the TDB was reduced, in the best case up to 52 %.