Time-stepping finite element analysis on iron loss distribution of cage induction motors

To study iron loss distribution characteristics in stator and rotor cores of cage induction motors, this paper establishes a computational model, with skew rotor bars considered, based on Time-Stepping Finite Elements Method (T-S FEM). Taking a 5.5kW cage induction motor as an example, time variations and loci of the flux density at different core locations is analyzed with no-load and full-load conditions, then the loss density and iron loss distribution in different locations in stator and rotor cores is derived. It is shown that high loss density appears in the middle of the tooth top for both the stator and rotor cores. Furthermore, iron loss distributions in different core areas are compared. On the stator side, iron losses mainly distributes at the boundary between teeth and yoke, in yoke and in tooth bodies, respectively occupying a proportion of 32%, 28% and 17.5% of the total calculated iron loss with no-load condition and 28.6%, 23.8% and 15.4% with full-load condition. On the rotor side, iron losses in the tooth top area caused by harmonic fields contributes 15% and 19% to the overall iron loss of the machine, with no-load and full-load conditions respectively. Experiments are performed on a special prototype motor, and the effectiveness and correctness of the above analysis is verified. The achievements could provide necessary technical supports for developing optimal design to reduce iron losses.