Throttle Valve Position Control System

A high-accuracy steam valve controller which uses a dc motor and gear train to position a steam valve shaft is described. The system responds to an error signal derived from the difference between an input reference and an output feedback signal. The error signal is amplified to control two firing pulse generators. The firing pulse generator's drive a set of eight SCRs in a dual bridge configuration, providing bidirectional armature drive for a 1/6-hp 115-volt dc motor. The system could easily be modified to handle larger motors by using larger devices in the dual bridge power circuit.