A balanced rotor assembly

摘要

A rotor assembly 1 for an electric machine such as a motor comprises a rotor 3 on a shaft 2 having a bearing 7, 8 at each end portion, the bearings being arranged to rotatably support the rotor and shaft. The assembly further comprises a balancing member 40, from which material may be removed for balancing the rotor assembly. The balancing member is located in a predetermined position and orientation with respect to the rotor. The balancing member includes an encoder disk 42, arranged to permit the position of the rotor with respect to a stator 13 to be determined. The provision of a balancing member having an integral encoder disk facilitates the manufacture of the rotor assembly. As the balancing member is located in a predetermined position, the encoder automatically assumes a predetermined position and hence the position of the rotor can be determined with certainty.