Rotor cage anomalies and unbalanced magnetic pull in single-phase induction motors. II. Experimental and theoretical studies

For pt. I see ibid., p.558-65, (1996). This paper consists of an experimental and theoretical investigation of the effect that rotor cage defects have on the unbalanced magnetic pull (UMP) present in a single phase motor. The model used in the theoretical studies is developed in a companion paper. In the experimental investigation, the UMP developed by a number of nominally identical motors that were known to have rotor defects, was measured using a specially designed test-rig. The rotors were then divided into two equal groups. The rotor bars in the first group were removed from the rotors, and their resistance measured to determine the range and distribution of porosity defects. The ovality of the rotors of the second group was carefully measured, and their end-rings turned off to enable the bar-to-bar resistance to be measured. This was done for all pairs of adjacent bars in the rotors of the second group, giving again an indication of the range and distribution of soldering defects. The range of bar and inter-bar resistances measured in the experimental investigation was then used to specify the data input to the theoretical model to investigate the likelihood that these defects are a major contributor to the UMP measured.