STARTING TORQUE OF THE INDUCTION MACHINE WITH STARTING DISC

Abstract

As it is well known, with the increase of the unit output, the relative starting torque (related to the nominal value) decreases in the induction machine with squirrel-cage rotor. This effect can be partially eliminated by using a new type patented rotor, having a starting disc. The disc, made of ferromagnetic material, is fixed to the shaft near the end rings of the single-cage basic machine. The discs can be regarded as a solid rotor where the stator is formed by the end windings of the basic machine. A further effect is that it causes skin effect in the neighbouring end rings (resistance increase in the rotor circuit of the basic machine). The increase of the starting torque is proportional to the sum of the eddy-current losses in the starting discs and the surplus loss in the end rings. The rotor, with starting discs, can be used with the best results for induction machines of high output and small pole number (Pn > 500 kW, p < 2).