Marine turbine control

A control system for a marine turbine power plant, said power plant having at least one ahead turbine and at least one astern turbine;

• each turbine having an output proportional to the flow of motive fluid through respective ahead and astern turbine inlet valves;
• said ahead and astern inlet valves selectively positioned by a valve position circuit according to a signal from said control system;
• said control system comprising:
• a throttle providing a first signal proportional to a desired valve position and a desired turbomachine shaft speed;
• means providing a second signal proportional to the actual turbomachine shaft speed;
• a speed feedback circuit including a first summing junction for combining said first and second signals to provide a third signal proportional to speed error;
• a second summing junction for combining said first and third signals to provide an inlet valve position signal;
• a malfunction proportional control providing an input signal to said second summing junction for modifying the inlet valve position signal;
• rate selection logic having inputs from said throttle and said malfunction proportional control, said rate selection logic providing an output rate selection signal in accordance with said throttle and malfunction proportional control inputs;
• and
• rate limiter means receiving said rate selection signal for applying said inlet valve position signal to said turbomachine inlet valve at a rate set by said rate selection logic.

The control system recited in claim 6 wherein the speed feedback circuit further comprises:

• first and second redundant speed pickups for providing said second signal actual speed input;
• digital means interconnecting said first and second speed pickups whereby the second speed pickup is enabled upon failure of the first speed pickup;
• logic means for disabling the speed feedback circuit upon failure of both speed pickups;
• direction control logic for controlling the polarity of the second signal actual speed input for ahead and astern operation;
• and,
• a threshold circuit through said logic means for disabling the speed feedback circuit when said first signal input exceeds an adjustable threshold value above the preset value of the signal limiter.

The control system recited in claim 15 wherein said rate limiter means comprises:

• an input amplifier for receiving the inlet valve position signal from said second summing junction;
• first, second, and third parallel rate selection channels corresponding to fast, normal and slow rates of valve operation, respectively;
• said rate selection determined by selective closure of switches according to the rate selection signal from said rate selection logic;
• an integrating amplifier receiving the output from at least one of said rate selection channels according to the rate selection signal the integrating amplifier output being input into said valve position circuit.

A control system for a marine turbine power plant, said power plant having at least one ahead turbine and at least one astern turbine;

• each turbine having an output proportional to the flow of motive fluid through respective ahead and astern turbine valves;
• said inlet valves selectively positioned by a valve positioning circuit according to an inlet valve control signal from said control system;
• and, said control system comprising:
• means for providing a first signal proportional to a throttle setting;
• means providing a second signal proportional to actual shaft speed;
• a speed feedback circuit including a first summing junction for comparing said first and second signals to provide a third signal proportional to speed error;
• a second summing junction for combining said first and third signals to provide an inlet valve control signal;
• rate limiter means having at least two selectable rates for applying said inlet valve control signal to said turbine valve positioning circuit;
• logic means for selecting at least one of said two rates depending upon said throttle setting and providing a rate selection signal to said rate limiter means.