Analysis of an induction motor with square wave currents in the rotor

A method of analysis for a slip ring induction motor with quasi square wave currents in the rotor and sinusoidal voltages in the stator is presented using the machine equations in terms of Park´s vector. A close form solution to the stator flux linkage is obtained. The analysis shows that the stator currents are essentially sinusoidal superimposed by slip dependent harmonics. The torque developed is found to contain pulsations both at six times and twelve times the rotor frequency. At lower speeds where the rotor frequency is large, the higher order torque pulsations become insignificant. At very low rotor frequencies, the frequency range of these pulsations may cause dangerous vibrations.