Some Considerations in the Design of Damper Windings for Synchronous Motors

As the application of synchronous motors is extended to include more specialized fields, the design of damper windings for special starting performance becomes more of an exact art. Methods have been presented before the Institute by which the starting performance can be determined with good accuracy. The purpose of this paper is to present certain possibilities and limitations of the performance which may be obtained by variation of the damper winding design. For purposes of consideration, damper windings are arbitrarily classified as low reactance and high reactance types. It is pointed out that low reactance damper windings are well suited to give a high ratio of torque to kva., especially during the initial part of the starting period. Many other types of performance, including a fairly uniform torque over the starting period or, a low starting torque with high pull-in torque-all with a relatively low kva. can be obtained with high reactance windings.