Analysis and effects of inter-bar current and skew on a long skewed-rotor induction motor for pump applications

This paper describes an investigation into the reasons for the reduction in starting torque of a very long skewed-rotor induction machine. It was previously assumed that inter-bar currents were the reason for the torque reduction and this is investigated by variation of the inter-bar resistance and also inclusion of inter-bar inductance. However, the fabrication process meant that the inter-bar resistance is high, and the simulation results for this machine illustrate that it is not true in this instance. It is found that several skew effects account for the reduction in torque and this is investigated in a variety of ways. In addition, the fitting of a large-diameter shaft is investigated.