Influence of the Rotor Slot Numbers on the Parasitic Torques and the Radial Magnetic Forces of the Squirrel Cage Induction Motor; an Analytic Approach

Studies regarding the right rotor slot number continues today although the so-called slot number rules were developed long ago. This paper examines the changes in asynchronous and synchronous parasitic torques and radial magnetic forces as a function of the mathematically continuously changing rotor slot number, by an analytical method using the formulas outlined in previous works of the author. It is suggested whether - in terms of subject phenomena only – a rotor slot number greater or less than the stator slot number should be used. A new theorem was derived that including and above the first stator slot harmonic the rotor fields they generate do not have to be taken into account when calculating subject phenomena. The paper provides a new method for incorporating fractional sub harmonics and harmonics caused by fractionalslot winding (although rarely used in induction motors) into the calculations based on the physical background.