The effects of inter-bar currents in cast aluminium and cast copper rotors

In this paper, a study of the influence of inter-bar currents on induction machines with aluminium and copper casted rotors is presented. The resistance between the rotor bar and the iron core is measured on five different rotors. An analytical model to predict the influence of inter-bar currents on machine performance is developed, and the results are verified by measurements. It is found that the measured inter-bar resistance is lower in cast copper rotors than in cast aluminium rotors. This leads to a reduced pull-out torque and increased stray-load losses.