Starting Performance of Salient-Pole Synchronous Motors

This paper presents an analysis of the sub-synchro-nous speed phenomena of a salient pole synchronous motor in which formulas and equivalent circuits are developed, making it possible to calculate the torque and current for a broad range of Conditions. Equations in terms of the impedances of the direct and quadrature axes are first derived from the revolving field point of view. The equivalent circuits for the two axes are then set up and expressions for the separate impedances of the circuit elements established. Adequate means of taking into account the combined effects of salient poles, incomplete amortisseur windings, and open or closed field windings are presented. The results obtained are illustrated by a comparison of the predicted performance and test data for a large 60-pole motor. The calculated distribution of current between the amortisseur bars of the same motor is shown by curves. Other curves show the calculated performance of the motor with and without continuous end rings between the poles and with the field winding open and closed. A final example shows the theoretical effects of changing the positions of the bars in the poles of a large waterwheel generator.