VACUUM PUMP

摘要

A vacuum pump (1) comprises first and second Northey mechanism rotor assemblies (4, 5). Each rotor assembly is mounted on a drive shaft (2, 3), each drive shaft being independently driven by a respective synchronous motor (8, 9). The shafts contra-rotate in use such that the rotor assemblies intermesh. A controller (12) is provided for controlling the frequency of the voltage supplied to each motor.