Speed-Torque Calculations for Induction Motors with Part Windings [includes discussion]

Test and calculated speed-torque curves are given for two 3-phase induction motors with part-winding starting. A 6-pole 300-horsepower (hp) motor was tested with three different winding arrangements: 1. full winding; 2. part winding, omitting alternate phase belts; and 3, part winding, omitting alternate slots. A 4-pole 40-hp motor was tested with the alternate slot connection. The individual field harmonics of each winding arrangement were obtained by Fourier series analysis, and an equivalent circuit for the entire winding was developed by connecting the circuits for the individual harmonics in series. The calculated speed-torque curves derived from these equivalent circuits check the test data with satisfactory accuracy.