Asynchronous and single-phase operation of synchronous machines

ASYNCHRONOUS operation of synchronous machines has been the subject of numerous articles in the technical literature, for example, the articles of Fechheimer,¹ Hay and Mowdawalla,² Putman,³ Park,⁴ Linville,⁵ Lauder⁶. The fact that articles on this subject continue to be of primary interest to design and operating engineers is attributable to the importance of satisfactory operation at asynchronous speeds. It is only through a precise knowledge of the conditions present in asynchronous operation that machines can be designed for and operated through these asynchronous periods satisfactorily. As examples of the extreme conditions which can arise during asynchronous operation, it should be noted that stalling a synchronous machine with the field voltage applied can result in pulsating torques greater than those obtained by inadvertent synchronizing 180° out of phase;⁶ or that the currents in the damper bars on the trailing half of a pole can be considerably greater than the currents in the corresponding bars on the leading half of the pole, and the resulting unequal heating will influence the design of the damper winding to a considerable degree. Because of the importance of these and similar phenomena, the problem of asynchronous operation must be studied continuously until a complete, easily visualized, and easily applied solution is obtained.