Dampins and synchronizing torques of power selsyns

SELSYN systems are used very widely as power drives and as indicators when it is necessary to have the position of an element correspond synchronously with that of a controlling element which is remotely located. The receiver Selsyn is used either directly as the output driving motor or as an input to a following power-amplifying stage of a control system.
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In the study of such Selsyn systems and of the control systems of which Selsyn systems form one of the links, it becomes necessary to determine the hunting-torque characteristics of these machines (that is, the damping and synchronizing torques for small oscillations) as affected by speed, load, oscillation frequency, and, of course, the various design factors. The direct calculation of these hunting-torque characteristics is difficult, but within the past few years methods have been developed whereby the machine performance may be represented by equivalent static electric circuits. The purposes of this paper are: 1. To show how these hunting-torque characteristics can be simply determined by measurements on equivalent electric circuits set up on an a-c network analyzer. 2. To present some of the results of studies made of specific Selsyn systems.