Optimal Rotor Bars Number in Four Pole Cage Induction Motor with 36 Stator Slots - Part I: Numerical Modeling

The identification of the optimal number of rotor bars in grid-fed, four-poles, three-phase cage induction motor is addressed in this two-part work for the frequent case of 36 stator slots. The optimization criterion being adopted is the minimization of the electromagnetic torque pulsations in full-load steady-state conditions. In Part I of the work results from the parameterized winding function (PWF) model are presented and successfully validated against time-stepping finite element simulations. In Part II the electromagnetic torque pulsations obtained from the PWF model are evaluated for different numbers of rotor bars. During this process motor rated power, stator winding design and main machine geometry are maintained invariant. The evaluation is applied to both possible practical cases of unskewed rotor bars and rotor bars that are skewed by one stator slot pitch.