Abstract: A system and method for operating a turbine power plant, wherein a demand signal based upon load or total turbine steam flow required for a predetermined level of operation controls the value of individual signals representative of valve position for respective steam inlet valves in the single and sequential mode of operation, is disclosed. Each individual valve position signal, which is representative of a selected portion of the total demand signal, is dynamically calculated to reflect the effect of the pressure drop across the nozzles, and to correct for the number of inlet nozzles, associated with each valve. The total demand signal is modified in accordance with actual throttle pressure over a period of time that is dependent on the amount of throttle pressure change.

Abstract: A control system for a steam turbine is disclosed which is operative to protect the turbine from the effects of sudden changes in steam supply pressure, and in particular to protect the turbine from the effects of water induction such as occurs with a sudden drop in steam pressure supplied by a boiler. In a preferred embodiment, a signal is created which represents the time rate of change of steam supply pressure. This derivative signal is compared with a preselected threshold value to produce a pulse signal whose duty cycle is proportional to the amount by which the rate of change of pressure exceeds the preselected threshold value. The pulse signal causes a proportional pulsing of a motor adapted to reduce a turbine load limit and effect a closing of steam admission control valves to counteract the change in steam pressure and reduce the potential for passing wet steam to the turbine.

Abstract: A method of limiting the discharge pressure for turbo compressors by means of a blowoff control which is controlled by an anti-surge controller along with means for measuring the discharge pressure and an extreme value selector as well as means for measuring the pressure flow rate and for generating a signal from a manual controller, comprises, measuring the discharge pressure, comparing the measured pressure with a desired maximum pressure to produce a pressure control signal, measuring the compressor flow rate, comparing the measured flow rate with a minimum permissible flow rate to provide a flow rate control, directing a signal from a manual controller to the value selector to generate a manual controller signal and feeding each of the pressure control signal, flow rate control signal, and manual controller signal to the anti-surge controller to provide a control of the blowoff valve in accordance therewith.

Abstract: A turbine control system which includes dual controllers having microcomputer processing circuits and capable of transmitting and receiving digital information to and from a plurality of valve position control circuits, also including their own microcomputer circuitry for controlling turbine steam admission valves. An operator's panel provides for two levels of automatic control as well as a manual backup which is communicative directly with all of the valve position control circuits. Overspeed protection control as well as fast valving is provided by redundant speed control circuits.

Abstract: An adjustable surge and capacity control system for matching a capacity control system to an inverter-driven centrifugal compressor based liquid chiller having unknown surge characteristics. The necessary adaptation of the capacity control circuit to a particular chiller is attained by the provision of two potentiometers which are adjustable to develop a functional which avoids surge and operates the system in an efficient manner at all feasible operating point loads and heads. The use of a circuit employing a pair of potentiometers permits the formation of the appropriate functional with two degrees of shaping flexibility.

Abstract: A control apparatus comprises a primary control unit composed of wicket gates of a hydraulic turbine and a secondary control unit composed of a bypass valve which is operated to open or close in cooperation with the opening or closing of the wicket gates. First and second link mechanisms are provided between the wicket gates and a hydraulic pressure distributor valve which is operatively connected to the bypass valve to control opening or closing of the latter. The first link mechanism detects the opening or closing motion of the wicket gates and transmits the corresponding signal to the hydraulic pressure distributor valve for the bypass valve, while the second link mechanism detect position of a pressure distributor valve plunger for the wicket gates and transmits the corresponding signal to the distributor valve for the bypass valve.

Abstract: A stress controlling system for a rotor of a steam turbine determines thermal and rotational conditions of the rotor. Thermal and centrifugal stresses produced in the rotor during operation of the steam turbine are calculated from the thermal and rotational conditions, respectively, of the rotor. Also, brittle fracture toughness of the material of the rotor under the thermal condition determined is calculated. Operation of the steam turbine is controlled to prevent the calculated brittle fracture toughness from being exceeded by the combined stress of thermal and centrifugal stresses during operation of the steam turbine.

Abstract: A diesel engine which may, for example, be a V-12 engine, is provided with a turbocharger having two sections, a turbine section which receives exhaust gases and which drives the associated compressor section. The turbocharger increases the input air pressure to the input manifold of the diesel engine up to several times atmospheric pressure. Both the turbine section and the compressor section of the turbocharger have adjustable vanes to vary the coupling with the exhaust gases, in the case of the turbine section, and with respect to the input air in the case of the compressor. An associated control circuit senses the temperature at the inlet to the turbine (the engine exhaust temperature), the speed of the engine, and the engine inlet manifold pressure, and adjusts the orientation of the turbine and compressor vanes for optimal engine performance, while avoiding cavitation or "stall" conditions in the compressor.

Abstract: A method of controlling the operation of multistage centrifugal compressor equipment provided with inlet guide vanes and diffuser vanes at each stage to enable operation to be practiced at a low energy consumption level. The method includes the steps of determining whether the prevailing flow rate, for example, is in a range of flow rates near the desired flow rate or in a range of flow rates remote therefrom; and controlling a combination of the amount of operation of the guide vanes with the amount of operation of the diffuser vanes, which is set beforehand, when the prevailing flow rate is determined to be in the latter range to promptly bring the prevailing flow rate to the desired flow rate level, and effecting fine adjustments of the inlet guide vanes and diffuser vanes to control the angles thereof when the prevailing flow rate is determined to be in the former range, thereby enabling increased efficiency to be achieved in the operation of the compressor equipment.

Abstract: A linkage system for the variable stator vanes of a gas turbine engine is augmented by control means operable as a function of compressor speed designed to match the aerodynamic requirements of the airflow through the compressor so as to define the rate of schedule change of the vanes over its angular movement by compensating for the inadequacies inherent in the capabilities of the linkage system.

Abstract: A dedicated supervisory control system for a steam turbine-generator comprising a hierarchy of microcomputer subsystems interactive with a conventional analog electrohydraulic control system to provide control and monitoring capabilities during all operating phases of the turbine-generator. The separate microcomputer subsystems are programmed for coordinated interaction and communication through shared, dual-port read/write memory units and each microcomputer subsystem is programmed and configured to handle a separate group of control responsibilities in a distributed control system.

Abstract: An adjustable surge and capacity control system for matching a capacity control system to an inverter-driven centrifugal compressor based liquid chiller having unknown surge characteristics. The necessary adaptation of the capacity control circuit to a particular chiller is attained by the provision of two potentiometers which are adjustable to develop a function which avoids surge and operates the system in an efficient manner at all feasible operating point loads and heads. The use of a circuit employing a pair of potentiometers permits the formation of the appropriate function with two degrees of shaping flexibility.

Abstract: A method and apparatus for regulating a steam turbine comprising at least one resuperheater arranged between a high pressure section and a low pressure section and in which a reference-actual value comparison of the rotational speed is performed to produce an adjustment signal derived from the reference value actual-value difference which is delivered from the difference between the impeller casing pressure of the high pressure section and the output pressure of the resuperheater which feedback signal is coupled into the regulation circuit opposite to the adjustment signal.

Abstract: The proposed method for automatic control of a power plant is as follows. A control signal of the electric generator's electric load is applied to a first control element which controls the flow of gas supplied from the gas line to the high-pressure section of an expansion engine. This controls the amount of gas directed from the take-off chamber of the expansion engine to the gas pipeline. A control signal to control the pressure downstream of the expansion engine is applied to a second control element to control the flow rate of the gas flow directed from the low-pressure section of the expansion engine to the controlled counter-pressure line. A control signal to control the pressure downstream of the expansion engine is applied to a third control element to control the gas flow rate, which is installed in the line that bypasses the low-pressure section of the expansion engine, whereby the rest of the gas flow is directed to the controlled counterpressure line.

Abstract: A fan control system for cooling apparatus such as cooling tower in which water and air are brought into contact together. According to this system, the running speed of the fan is continuously and proportionally changed responsive to the temperature of the cooling water or the external atmospheric conditions, to substantially control the cooling capacity of the cooling apparatus. The control system consists of a main fan motor, an electronic adjustment circuit and a power transmission means consisting of a variable pitch diameter belt speed changing means and a constant pitch belt reduction device, whereby the speed changing ratio of the belt speed chaning means is continuously and proportionally changed depending upon the control signals from the adjustment circuit. Further, the adjustment circuit may have a soft-start control circuit.

Abstract: A safety system for a steam turbine installation is disclosed based on a closed circuit principle and includes a two-channel low-pressure section in which safety devices are utilized and a high pressure section. Each channel of the low-pressure section acts hydraulically on the high pressure section by way of a tripping and reset relay. The high pressure section includes a high pressure hydraulic system and is divided into an intermediate safety system and a principal safety system each having a two channel arrangement. A one-channel common safety system is provided with stop valves for the steam turbine. Feed and discharge amplifiers are hydraulically connected in series and separate the intermediate and principal safety systems.

Abstract: The invention provides a method for operating a power generating assembly which assembly comprises a steam generator and a turbine, and said method comprises controlling the quantity of heat released by the steam generator by a signal which is representative of the difference between the predicted stresses which will exist at the instant to+T on that part of the turbine which undergoes the greatest thermal stress and the maximum permissible stress on this same part at the same instant, to being the present instant and T being a period of time close to the time constant of the power production assembly.

Abstract: In a system and method for automatically starting, synchronizing and operating a steam turbine, control means for valve position limiting wherein such limit can be changed non-linearly. Means are provided whereby the system operator has the ability to manually select a minimum incremental change of the valve position limit as a keyboard-entered constant. If the operator enables a continuing change in the limit it is introduced arithmetically, permitting large swings in a reasonably short period of time.

Abstract: A turbine speed control system comprising a pair of concurrently operable electronic microprocessor-based controllers which are coupled together by a data link to functionally cooperate in controlling turbine acceleration primarily during start-up operations in accordance with a set of predetermined measured and calculated turbine conditions. One controller is operative to control the speed of the turbine at selected accelerations from turning gear to a predetermined speed value. This same controller monitors a plurality of temperature differences from preselected regions of the turbine and inhibits turbine acceleration in accordance with an out-of-limit temperature condition associated therewith. In addition, the one controller is further operative to selectively override the turbine speed hold initiated by an out-of-limit temperature condition, the override permitting the one controller to proceed with controlling the speed of the turbine at a desired acceleration.

Abstract: A stall control system for axial flow compressors incorporating: a plurality of pressure transducers for developing signals indicative of the nonsteady pressure variations within the compressor and wherein these signals are separately filtered and rectified; analog comparators and gate comparators for each such signal to develop an output indicative of the difference between each of the signals and an adjusted pressure reference signal which is derived from the pressure rise across the compressor; a logic circuit for generating an actuating signal if any one of such signals is higher than the reference signal for controlling the opening of a gate which passes the combined pressure signals to an integrator which develops an output control signal to take corrective action in the presence of rotating stall within the compressor: an adjustable time delay circuit providing long and short decay times to prevent over-control.

Abstract: A forced air heating and/or cooling system in a building is provided with the usual main supply conduits or duct which have various branch ducts leading to different areas of the building. Pressure sensitive instruments at spaced locations in the main supply duct are connected by electrical wiring or pneumatic tubing to a comparing instrument which senses pressure signals from the different zones determining the maximum required pressure that must be supplied to the system. Zone thermostats sense increases in room temperature and operate conventional variable volume boxes to increase the supply of air thereby lowering the air pressure. The comparing instrument sends a signal to a variable speed drive comprising a motor having a spring loaded pulley connected by a drive belt to a fan pulley and the motor is electrically driven by a separate drive means to adjust the tension on the spring loaded pulley thereby changing the speed of the fan for a more economical operation.

Abstract: A method of, and apparatus for, regulating a resuperheated steam turbine wherein there is carried out a reference value-actual value comparison of the rotational speed and there is derived an adjustment or control magnitude from the reference value-actual value difference, this adjustment magnitude being infed to a regulation valve arrangement. There is derived from the resuperheated pressure a feedback magnitude which, as a function of time, yields to null and is coupled into a regulation circuit opposite to the adjustment magnitude.

Abstract: Present speed and present steam temperature are utilized in accordance with a mathematical model to evaluate present steam to turbine heat transfer and turbine heat propagation quantities, and present turbine rotor and casing surface and volume average temperatures. The model is corrected for inaccuracy based on comparison of calculated rotor to casing differential expansion with measured values, and is exercised once more with anticipated speed and steam temperature quantities to develop anticipated rotor to casing differential expansion and anticipated rotor stress. These quantities are compared with various predetermined limits to determine whether the present and anticipated speed and acceleration are within allowable limits.

Abstract: Apparatus and method for automatically determining and indicating that the rotor of a steam turbine has attained a predetermined minimal temperature. Means are utilized for measuring axial dimensional changes of the steam turbine cylinder and rotor due to an increased temperature and summing pertinent axial dimensional changes thereby determining the axial expansion of the rotor which in turn, through known physical properties of the rotor material, corresponds to a temperature increase. This increase of the temperature added to the initial temperature of the rotor provides the total temperature, and upon the total temperature reaching a predetermined value, the steam turbine is available to be brought up to speed and loaded.

Abstract: Surge control systems prevent and control a surge condition for fixed or variable speed compressors and compressors having variable geometry which provide air to pneumatic loads. A signal proportional to the ratio of the measured compressor outlet pressure to the measured inlet pressure is combined with a signal corresponding to a selected reference pressure to provide a vent valve command signal. When the signal representing the ratio of the measured pressure exceeds the signal corresponding to the selected reference pressure, a surge condition is developing and the vent valve command signal causes a valve to vent a portion of the air to the pneumatic load. The venting of the air reduces the measured pressure ratio and the vent valve command signal decreases, to close the valve. A signal is provided to reduce the effect of the reference pressure ratio if the weight flow rate through the compressor is reduced, as by decreasing compressor speed and/or repositioning the inlet guide vanes of the compressor.

Abstract: Surge control systems are provided for compressors which supply air to a pneumatic load. A signal proportional to the pressure ratio of the outlet pressure to the inlet pressure plus a selected reference pressure is compared to a measured weight flow rate of air through the compressor to provide a vent valve command signal. If the measured pressure ratio plus the reference pressure ratio exceeds the measured flow rate, a surge condition may ensue. The vent valve position command signal causes a venting valve to vent a portion of the air provided to the load, which reduces the measured pressure ratio and increases weight flow rate. During normal operation of the compressor, the vent valve command signal is zero for all values of weight flow rate. A transient control channel is provided which is responsive to the rate of change of the measured pressure ratio and/or measured weight flow rate.

Abstract: A surge control system for controlling and preventing a surge condition and a method of controlling surge in a fixed or variable speed compressor or a compressor having a variable geometry which provides air to a pneumatic load. A transducer provides a signal proportional to the outlet pressure of the air from the compressor. The signal is differentiated with respect to time and if a surge condition is ensuing, the absolute value of the differentiated signal is greater than a reference. When the differentiated signal is greater than the reference, a portion of the air supplied to the load is vented to reduce the outlet pressure. A reduction in the outlet pressure alleviates the ensuing surge condition and the absolute value of the differentiated signal decreases, causing the venting valve to close.

Abstract: Surging of a centrifugal compressor is avoided by ensuring that in operation ##EQU1## WHERE K and k are parameters whose values depend on the characteristics of the compressor, g is the acceleration due to gravity, h.sub.p is the polytropic head produced by the compressor, Vc is the velocity of sound in said inlet gas, and Mn (the Mach Number) is the ratio of the flow velocity V of the gas at the inlet to the compressor to the velocity of sound Vc therein. This is normally effected by arranging that ##EQU2## where .DELTA..sub.p is the differential pressure across a throttling member disposed in an inlet duct of the compressor, P.sub.1 is the compressor inlet pressure, and P.sub.2 is the compressor outlet pressure.

Abstract: An integral plus proportional control system responding to more than one variable controls a single actuator wherein the integral gain is selected in accordance with the error of that variable which is being controlled to compensate for varying process dynamics. An error selector serves to discriminate the error signal which is being controlled and synchronously selects the gain of the integrator.

Abstract: An isolated electrical power generation system is described with multiple isochronous, load-sharing engine-generator units. The system includes load sensing means for generating a signal representing the individual power output of each engine-generator unit, means for generating a signal representing the total power output of all the engine-generator units in the system, and load-sharing means responsive to deviations between each individual power output signal and the total power output signal for controlling the fuel inputs to the respective engines in the various units. A load simulating means responds to the occurrence of a preselected condition, such as an excessive temperature, in an individual unit for adding a simulated power output signal to the individual power output signal for that particular unit.

Abstract: An improved high-water-level trip control for a steam turbine is disclosed. Instead of causing a trip of the turbine (or reactor) based merely on the water level in the steam generator, the present invention generates a trip command that is based on a function of more than one parameter. Such a function more accurately indicates the quantity of water droplets in the steam leaving the steam generator than a function of a single parameter does. In particular, it is disclosed to trip the turbine when the water level exceeds a variable reference that increases as steam velocity decreases; this takes into account the effect of steam velocity on the entrainment of water droplets by the steam.

Abstract: At the point of time to when the turbine speed has come up to a first speed N.sub.1, a thermal stress expected in the turbine when the speed is increased to a second speed N.sub.2 at a rate .alpha..sub.1 is presumed. Thermal stress .sigma..sub.s(t) -.sigma..sub.sT1 at the point of time t.sub.o1 for commencing acceleration to the second speed N.sub.2 is then obtained, which point of time t.sub.o1 would never cause the maximum value of the presumed thermal stress to exceed a predetermined limit .sigma..sub.sl of the thermal stress when the turbine speed is increased at that rate. Then, a length of time T.sub.w1, referred to as a warming time, is determined which is required for the thermal stress .sigma..sub.s(t) to decrease to the level of (.sigma..sub.s(t) -.sigma..sub.sT1) when the warming is continued after the point of time t.sub.o. Subsequently, a length of time (N.sub.2 -N.sub.1)/.alpha..sub.1 required for increasing the turbine speed from N.sub.1 to N.sub.2 at the rate .alpha..sub.1 is calculated.

Abstract: In a steam turbine-generator with means for determining a load demand signal in accordance with a load reference signal, means for determining the valve opening under each admission mode of full-arc and partial-arc in accordance with said load demand signal and means for adjusting the ratio between valve openings under the each admission mode in accordance with a load change the ratio of steam flow under each of the admission modes is controlled in accordance with a load change so as to minimize the thermal stresses and thereby reduce the turbine load changing time.

Abstract: In a control system for a hydroelectric power station system including upper and lower water reservoirs connected through a water channel, an intermediate water reservoir having a smaller storage capacity than those of the upper and lower reservoirs and provided on the water channel in cascade with the upper and lower reservoirs, and two power stations disposed between the upper and intermediate reservoirs and between the intermediate and lower reservoirs, respectively, the control system is arranged such that the water level of the intermediate reservoir is detected continuously and the detected value of the water level is used to correct the load instructions which are applied to the power stations for controlling outputs of the power stations whereby the water level of the intermediate reservoir is maintained substantially constant, while the power generation of the power stations is controlled so as to satisfactorily meet with the load instruction applied to the power system.

Abstract: A centrifugal pump includes a housing containing an impeller mounted on a shaft which is journaled for rotation within the housing. An inlet to the housing directs fluid from a supply to one end of the impeller and axially spaced first and second volute diffusers formed around the other end of the impeller receive fluid from the impeller. The volute diffusers are of different predetermined sizes designed to handle different flowrates of fluid while producing about the same pressure head. A sleeve telescoped into the housing and surrounding the impeller may be moved between extended and retracted positions to close off and open the flow of fluid into the larger one of the volute diffusers.

Abstract: Method and apparatus for controlling the set point for steam temperatures for cold start-up of a steam generator-turbine unit wherein inlet steam temperature and turbine load absorption are steadily and substantially simultaneously increased in accordance with a predetermined relationship so as to reach their final values substantially synchronously.

Abstract: A turbine control system incorporating a speed monitoring system for generating an actual turbine speed measurement for control of turbine speed and load is disclosed. The speed monitoring system employs two identical speed channels each of both analog and digital form and a third channel of only analog form. The two identical speed channels of digital form and the third channel of analog form are coupled to a programmed digital computer based process controller for use in controlling turbine speed and load. The two identical speed channels of analog form and the third channel are coupled to an overspeed protection controller for use in preventing turbine overspeed. Within each controller, an identical channel is selected without preference to be used as the actual turbine speed measurement. A transfer between identical speed channels will only be performed if a malfunction is detected in that identical channel utilized as the actual turbine speed measurement.

Abstract: A system for detecting the failure of steam inlet valves to respond properly to their respective control signals, is disclosed. The detection of such a contingency provides an appropriate indication, and also initiates a transfer to single valve operation when operating in the sequential valve mode. The system provides for indicating and/or transferring to single valve operations only after the contingency has been detected for a predetermined interval to compensate for the velocity limiting characteristics of the valve actuators.

Abstract: A method and apparatus for protecting a dynamic compressor from surge. The method includes a first step for providing a simultaneous control of a smaller relief means and a main control member of a dynamic compressor or the driver thereof for changing the performance of the compressor. This combined action provides for the protection from surge and at the same time insures the invariability of the main control parameters of pressure, mass flow rate to the user, or the speed of rotation. The second step provides for controlling a larger relief means and provides for antisurge protection in those cases when the first step is not sufficient to protect the compressor from surge. Apparatus is also provided for automatically implementing the method.

Abstract: An electric power plant having dual turbine-generators and a steam source which includes a high temperature gas-cooled nuclear reactor. Each turbine includes a high pressure portion driven by superheat steam and a lower pressure portion driven by reheat steam. A turbine bypass system permits minimum flows of superheat and reheat steam from the source at times when the turbines require flows of such steam that are less than the minimum flows. Before it is reheated, steam that has passed through the high pressure portions and their bypass lines drives auxiliary steam turbines that rotate means for propelling the coolant gas through the reactor. During acceleration of a turbine-generator to its synchronous speed, one of the steam flows through its high and lower pressure portions is varied to govern the shaft speed, while the other flow is held relatively constant, that one of the flows which is varied being determined by the shaft speed.

Abstract: An improved automatic fuel shutoff system is provided for a turbine type power plant which incorporates (1) sensing means responsive to a preselected abnormal engine operating condition for initially cutting off fuel flow to the engine and (2) latching means for maintaining the cutoff until engine conditions favorable for a normal restart are obtained.

Abstract: An electric power plant steam turbine system with digital computer control in which control signals are generated as a function of the actual steam conditions present in each turbine section and in a manner which maintains the sum of the instantaneous power developed in each turbine section equal to the total demand placed upon the turbine system.

Abstract: In a plant of a composite cycle which includes a steam turbine having a high pressure portion and a low pressure portion, a gas turbine, and a waste heat boiler having heat exchangers producing high pressure steam and low pressure steam to be fed to the steam turbine, by the use of exhaust gas from the gas turbine as a heat source; there are provided steam valves on steam passages through which steam is fed from the heat exchangers of waste heat boiler to the steam turbine; a detecting device for detecting the condition of steam flowing into the steam valve; and another detecting device for detecting the r.p.m. of the steam turbine; whereby the opening and closing of the steam valves are controlled by means of a selecting device which preferentially selects either of signals from the aforesaid detecting devices to adjust the quantity of steam to be fed to the steam turbine for controlling the steam turbine.

Abstract: A reversible cycle ice making machine provided with a tube-in-tube evaporator having disposed between the tubes thereof an annular chamber through which a refrigerant is adapted to flow and bond a hollow ice column upon the inside surface of the inner tube during the freezing cycle; and during the succeeding defrost cycle, to thaw the bond by a dual acting defrost system.One of the defrost actions of the system is effected by flowing a defrost fluid, such as hot gas, endwise through the annular chamber to cause the refrigerant remaining the chamber from the preceding freezing cycle to be progressively replaced by the defrost fluid while the ice column bond is progressively thawed in the endwise direction. Thus, the length of the chamber containing the defrosting fluid progressively increases as the complementary length containing the remaining refrigerant fluid decreases during the flow of both fluids in tandem and downstream through the chamber.

Abstract: The speed of an engine driven pump is sensed and compared with the desired maximum operating speed to detect overspeed. The discharge of the pump is controlled by a variable flow rate controller. When an overspeed condition exists, a command signal is sent to the discharge controller to reduce flow by a discrete decrement. The control signal is blocked after activating the controller for a preselected time interval. During the blocking interval the engine speed is maintained substantially at the operating speed by cyclical reduction of the power input thereto.

Abstract: A turbine control system for changing two speed governing operations of a steam turbine from a throttle governing operation to a nozzle governing operation and vise versa by controlling steam control valves comprises function generators grouped according to the two speed governing operations and operated by a main control flow-rate request signal to produce function outputs which are applied to respective low-value gate circuits, means for comparing the sum of the outputs of the gate circuits and the main control flowrate request signal, and means for varying the main control flowrate request signal with the aid of the difference between the signals thus compared in such a manner that while one of the outputs of the gate circuits decreases, the other output increases to supplement the decrease, whereby the steam control valves are gradually operated with the output of the turbine being kept unchanged during the operating mode changing operation.

Abstract: A control system for an extraction type steam turbine driven by steam from a steam generator wherein it is desired to control the steam pressure in the steam generator, at a predetermined level, by varying the position of the steam inlet valve. Turbine speed may be controlled at a predetermined level by varying the position of an extraction control valve. The inlet valve and the extraction valve are independently operable except under a condition where the extraction valve is completely closed and the turbine speed continues to rise. In this instance, means are provided for positioning the inlet valve according to a speed control signal which dominates an inlet pressure control signal for lowering the inlet steam valve until normal conditions are restored.

Abstract: A system for detecting turbine compressor surge wherein a transducer produces a signal in response to discharge pressure fluctuations and depending upon the magnitude and frequency of the signals the compressor flow and pressure rise is regulated.

Abstract: A gas turbine power plant is provided with an industrial gas turbine which drives a generator coupled to a power system through a breaker. The turbine-generator plant is operated by a hybrid control system having digital function capability during sequenced startup, synchronizing, load buildup and steady state load, and shutdown operations. The control system also contains monitoring and protective subsystems which function through all stages of operation, with redundancy and permissive features which maximize turbine availability.

Abstract: An automatic control system for high pressure blower applications prevents surging under variable supply flow rate requirements and achieves maximum efficiency of operation. The supply flow rate establishes the set point of a proportional plus reset controller, the latter receiving a feedback signal corresponding to the static discharge pressure of the supply blower and responding thereto for controlling the output of the supply blower. A return blower is controlled either through a characterizer relay in proportion to the control of the supply blower to maintain a fixed precalibrated relationship between supply and return flow rates or by a further proportional plus reset controller responsive to the supply flow rate, for establishing the set point thereof, and to the return flow rate, as a feedback signal thereto, for controlling the output of the return blower.