Non-linear model of rotor delevitation in an active magnetic bearing system including parameter estimation

Backup bearings (BBs) are used to protect active magnetic bearings in the event of rotor delevitation. To gain insight into the design, selection and operation of BBs, a model that can accurately simulate the behaviour of a rotor and BB system during a rotor delevitation event is required. This paper presents a model that can accurately simulate rotor delevitation and predict the occurrence of forward and backward whirl. The model, called BBSim, is based on the integration of a number of simpler models for each of the important mechanisms that govern the behaviour of a BB system. Estimation of parameters that are critical in determining the rotor's behaviour inside the BB clearance is achieved using empirical methods. Rotor orbit plots confirm the model's capability of simulating the characteristic motions of rotor delevitation.