Machine having a back-up bearing having a hybrid arrangement

A machine, comprising:

• a stator;
• a rotor having a rotor shaft and located radially inside the stator so that the stator extend over a whole length of the rotor;
• a bearing configured as active magnetic bearing to support the rotor shaft in a contactless manner for rotation about an axis of rotation;
• and
• a back-up bearing operably connected to the active magnetic bearing and configured to catch the rotor in the event of a failure of the active magnetic bearing, said back up bearing having a sliding device arranged directly on a radially inner surface of the stator and a bushing which is arranged radially inside the sliding device at a radial distance from the sliding device, said bushing having a radially inwardly arranged inner ring located directly on the rotor shaft to fasten and retain the bushing on the rotor shaft, an outer ring disposed in radially outwardly surrounding relationship to the inner ring at a radial distance from the sliding device to form a gap therebetween and configured to slide in the sliding device of the back-up bearing in the event of a failure of the active magnetic bearing in a surface-to-surface sliding contact
• between the outer ring of the bushing and the sliding device, and an intermediate layer arranged radially between the inner ring and the outer ring, said inner and outer rings of the bushing being made of different materials and joined to each other by a material bond formed by the intermediate layer.