Parameters of solid-rotor induction machines with unbalanced supply

The paper is directed towards appraisal of the tubular-axle induction motor (t.a.i.m.) with solid rotor when used with single-phase supply and a Ferraris-Arno phase conversion system for railway traction. A mathematical model is presented for solid-rotor induction machines with unbalanced supply. Some basic measurements are reported of the incremental permeability of steel under conditions where two alternating excitations of differing frequencies are superimposed. This data is used in a proposed method for calculating the negative-sequence impedance of the solid-rotor machine from design data. A new method is described for measuring the parameters of machines with unbalanced supply under actual operating conditions, and is shown to be very useful when variations due to magnetic saturation are significant. The theoretical work is verified by comparison with tests on both large and small machines (150 kW at 500 rev/min and 250 W at 1500 rev/min),and the application of the model in the simulation of traction systems is illustrated.