Abstract: A vacuum pump a the magnetic bearing assembly includes the magnetic bearing assembly with rotor position sensors and backup bearings being placed inside the rotatable shaft of the vacuum pump. The sensor placements are independent of the bearing position, so that the respective radial sensors can be at the same axial position as the respective radial bearings, which provides sensors co-location and a space saving within a turbopump housing, in particular, in its axial direction, while sensors and mechanical backup bearings are placed in a better protected area with respect to pumped corrosive gases.

Abstract: A vacuum pump has a back-up bearing assembly for allowing its rotor to spin down safely without damaging the pump if the primary bearing system becomes disabled. The drive shaft of the rotor is tubular and contains the back-up bearing assembly in its hollow interior. Back-up bearings are mounted onto a tubular center shaft which is coaxial with and inside the drive shaft. An axial position sensor is nested inside the center shaft and light emitted from its light emitter is reflected by a reflective target inside the drive shaft to detect the relative axial position of the drive shaft with respect to the center shaft. A polymer sleeve is attached to the end of the drive shaft as a thermal compensator, which restricts the axial movement of the drive shaft.