A new graphical approach to three phase two speed induction motor winding design

It has already been shown how to obtain 2-speed winding squirrel-cage induction motors using pole amplitude modulation (PAM) with 6 terminals to the winding. Phase modulation has been used as well to obtain 2-speed winding squirrel cage induction motors with simpler C-terminal change-over switch only. This paper presents a new powerful method (based on the graphical representation of phase distribution) which enables the designer to make his choice easily between PAM and PM. Particular example has been chosen for the presentation together with some experimental results obtained on a trial model.