Dynamic representation of a hydraulic constant-speed drive

The hydraulic constant-speed drive is an important component of many air-borne electric systems; it is used to convert the varying aircraft engine speed into a constant alternator shaft speed needed to maintain constant system frequency. To study the behavior of electric systems with isolated alternators and other systems with paralleled alternators, it has been necessary to find descriptions of the system components which may be translated into mathematical terms in a formulation convenient for block diagram representation and analog computer simulation. Descriptions of voltage regulators, exciters, alternators, and system load, have been developed and presented in the literature.1¿3 The purpose of this paper is the presentation of information about the hydraulic constant-speed drive and some associated components. The basic drive equations pertain to the ball drive, the axial piston drive, and to the radial piston drive. The equations of the ancillary equipment are pertinent to a particular model.