Digital transfer control system for dual mode turbine operation

Abstract

A digital transfer system for transferring the operation of a steam turbine between a single and sequential mode of operation is disclosed. A total flow demand signal is applied to all of the valves in parallel for the single mode; and applied to all of the valves through individual function generators for the sequential mode. A digital up/down counter is connected to a rate multiplier for generating pulses at a frequency corresponding to the status of the counter. An electronic switch is connected to conduct either the single or sequential mode signal to the valve operating mechanism to respond to the pulses for repetitively applying alternately the single and sequential mode signal during the transfer. Digital components both control and are controlled by the counter to increase incrementally the frequency of operation of the electronic switch to apply the particular signal toward which the transfer is being made at such increasing frequency during the first portion of the transfer period and to incrementally decrease the operating frequency of the switch and apply the particular signal from which the transfer is made during the final portion of the transfer. Provision is made to adjust the period of transfer; and to stop or reverse the transfer between modes at any period during the transfer.