Electric motor with reduced vibration for acoustically sensitive area - has asymmetric air gap for generating magnetic side thrust on output shaft to minimise effect of pulsed torque variation

摘要

The electric motor comprises a brushless dc drive with permanent magnet rotor (1) and pulsed stator winding (12) for generating a rotating magnetic field in stator (7). Troublesome rotor oscillations giving rise to noise are reduced by promoting a magnetic thrust at right angles to the rotor axis. The thrust holds the drive shaft (6) firmly but flexibly against the bearing areas of housing (8). The required side-thrust is produced by an asymmetric airgap and several methods of achieving this are described. USE/ADVANTAGE - In applications where quiet running is important. Is particularly effective where drive shaft is vertically mounted.