M.M.F.-harmonic effects in induction motors with phase-wound rotors

While the influence of m.m.f. harmonics on the winding inductances of practical induction motors with phase-wound secondaries is extremely small, their effect on the current waveforms may be profound. The problem posed by this phenomenon is readily stated in terms of dynamic circuit theory, but the standard transformation techniques do not facilitate a solution. A method of direct solution of the original timevarying-coefficient differential equations, based on an analytical solution for constant-current excitation, followed by an iterative process for conversion to constant-voltage excitation, is described. Experimentale evidence is advanced to show that the iterative process converges with great rapidity. Oscillograms of actual currents are compared with predicted waveforms, to demonstrate the validity of the technique