Design Construction and Testing of a Turbomolecular Pump with Five Axes Magnetic Suspension

A turbomolecular pump with five-axes magnetic suspension has been designed and built in 1993 as a result of a co-operation between the Elettrorava S.p.A. and the Laboratory for Mechatronics of Politecnico di Torino. The design and the construction of the pump are here described, together with some problems which have been encountered and solved during the construction stage. A dynamic analysis of the closedloop system has been performed before the construction to make sure that the system stability was achieved over the entire operational range. Two prototypes with a total rotor mass of about 10 kg running at 27000 rpm have been built and tested, and some minor modifications are now in process in order to start series-manufacturing. The tests on the prototypes have given very satisfactory results: vibration and power consumption are very low compared with a conventional turbomolecular pump with ball bearings, and the agreement between theoretical predictions and actual behaviour is very good.