Losses In Squirrel-Cage Motors Due To Rotor Skew

A discussion of the losses caused by skewing of a rotor with uninsulated bars is presented, giving full consideration to the distributed nature of the rotor parameters. At first, tooth pulsation and surface losses are reviewed briefly. Then an approximate method of calculation of losses due to iron cross currents in the rotor is presented and shown to yield experimentally acceptable results. The equations for the latter losses are relatively simple and the effect of parameter variations can be studied. The losses in the bars are shown to be inversely proportional to the square of the differential leakage coefficient of the rotor; the surface losses in the iron are a function of the resistance between adjacent bars of the squirrel cage and are inversely proportional to the first power of the differential leakage coefficient.