Constant Speed Drive

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Constant Speed Drive (CSD) is a device fitted between engine crankshaft (shaft) and the alternator to rotate the armature at constant RPM at different engine speeds so as to have constant number of cycles. Example steady 400 Hz current.

In an a-c power system it is usually necessary to maintain a fairly constant speed in the a-c generator.

The CSD, mainly used on aviation jet engine applications, consists of a variable output hydraulic pump driving a hydraulic motor, which, in turn, drives the generator. The output of the pump is determined by engine speed and governor position.