Abstract: A controlled current inverter system including an inverter circuit having controlled rectifiers for supplying an output of variable voltage and frequency for application to a load; e.g., an electric motor, further includes a variable direct current power source for supplying electrical power to the inverter circuit. Protection against overvoltage conditions of the inverter circuit rectifiers is provided as a function of the inverter output voltage, current and the electrical characteristics of a load supplied by the inverter circuit. This protection takes the form of circuitry which anticipates a potential overvoltage condition and acts to reduce the output of the direct current power source and inhibit the firing of the rectifiers of the inverter circuit until such time as the potential overvoltage condition is eliminated.

Abstract: A controlled current inverter system forms the basis of an a.c. motor drive system for furnishing the motor load with a variable frequency, variable magnitude a.c. current from an inverter which is supplied from a variable d.c. current source by way of a d.c. link including an inductor. Torque is the control parameter employed in the system and the motor speed and torque are controlled through the control of motor flux and motor current, by maintaining a controlled ratio between the direct and quadrature motor currents, through separate control paths to the d.c. source and the inverter. A third control path functioning on the difference between the desired and actual motor flux serves as a modifier to the main control paths to improve overall operation and control. Means associated with the basic control paths provide for dynamic braking of the motor.

Abstract: In association with a polyphase hybrid rectifying bridge having controlled rectifiers, there is employed, in addition to the normal means for controlling the firing time of the controlled rectifiers, additional circuitry for preventing or at least reducing the probability of the occurrence of a commutation fault. This is achieved by first producing a timing signal which is representative of the time intervals during which a voltage exists across a load being supplied by the bridge and by then combining the timing signal with a basic reference signal representing a minimum time period during which this voltage should exist to guard against a commutation failure of the controlled rectifiers. When a prescribed relationship exists between the timing signal and the basic reference signal, the normal control means is overridden and the firing angle of the controlled rectifiers is advanced to a point which will guarantee commutation.

Abstract: In association with a polyphase rectifying bridge having controlled rectifiers there is employed, in addition to the normal means for controlling the firing time of the controlled rectifiers, additional circuitry for preventing the occurrence of a commutation fault. This is achieved by first producing a timing signal representative of the time intervals during which a commutation between successively fired controlled rectifiers of the bridge actually exist. This timing signal, after being properly shaped is combined with a basic reference signal representative of a predetermined value to which the rectifiers may be phased back in their firing angle without resulting in a commutation failure. Stated in another way, the width of the existing commutation period serves to set a minimum to which the next commutation period must conform.

Abstract: A speed regulator and control system for controlling a motor from a polyphase AC source includes a data processor and a regulator and rectifier control interfacing the data processor with a controllable rectifier driving the motor is disclosed. The regulator and rectifier control, under control of the data processor, selectively transfers system parameters to the data processor, receives a calculated value proportional to firing angle from the data processor and supplies firing pulses to the rectifier to selectively connect each phase of the AC source to the motor as calculated by the data processor.

Abstract: A control or protection system for a line commutated inverter detects prescribed conduction-through faults and initiates a control sequence for recovery without shutting down the inverter. A conduction sensor in each leg provides a signal representing conduction and this is compared with a signal representing the forbidden interval when conduction should not occur in that leg. When conduction is detected in a forbidden interval it normally indicates a conduction-through fault and the gating pulses are advanced for at least the next two pulses to occur immediately but with a limit of 60.degree.. This causes commutation of the legs which are carrying the conduction-through fault current provided that sufficient volt-seconds remain in the alternating current part of the circuitry.

Abstract: A programmable data processor or controller serving as the main control in a control system contains an executive program for controlling the transfer of information between the processor and system equipment, updating that information during on-line control of the equipment and modifying the executive program to change operating parameters of the system while the data processor is controlling the system equipment. Modification of the executive program and displaying of system parameters relative to the executive program and the system equipment is accomplished through the use of an operator's console which communicates with the data processor and system equipment as a result of operator intervention.

Abstract: A controlled rectifier inverter system of the type in which the inverter circuit has capacitors across which voltages are developed as a function of the current output of the inverter, such voltages being utilized to commutate the rectifiers of the inverter circuit, includes means to limit the magnitude of the rise in output current between successive commutations of the rectifiers of a group to prevent the achievement of a current in excess of that which can be commutated by the voltages on the capacitors.

Abstract: A digital firing control circuit is disclosed for controlling the generation of firing pulses for the eight controlled rectifiers (thyristors) in a bridge power converter in five distinct operating modes as well as effecting a smooth continuous transition between modes. The circuit compares and combines a plurality of locally generated time related waveforms according to a predetermined control algorithm in response to an applied analog command voltage to control the d.c. output voltage as well as providing certain protection functions such as end stops or inversion limits. The locally generated time related waveforms comprise sets of square voltage signals generated in accordance with selected cross-overs of the line voltages of the a.c. sources as well as the cross-overs of six firing reference ramp voltage signals separated from each other by 60.degree. and extending 240 electrical degrees.

Abstract: A control system including a controller for reading temperature values from sensors in a gas turbine, determining the reliability of the sensors, and issuing a fuel control signal for use in controlling the turbine is disclosed. The fuel control signal has a calculated value which is a function of the turbine operating temperature derived from the values of temperature signals generated by the sensors.

Abstract: A semiconductor and heat sink assembly of the type having two groups of semiconductor devices only one group of which is operable at any instant in time has the semiconductor devices arranged, with respect to the heat sink portion of the assembly, in a divided manner such that maximum utilization is made of the heat sink to thereby provide improved duty cycle capabilities.

Abstract: A method of controlling the thyristors of an a.c. to d.c. bridge converter, having neutral connected thyristors, at relatively low power levels by gating each phase leg thyristor conductive for a predetermined minimum period within the electrical separation between adjacent line to neutral phase voltages and immediately gating the respective neutral leg thyristor conductive for the remainder of the period such that there are no intervals in the cycle when both neutral leg thyristors are in conduction. In a three phase bridge converter system, this requires at least 60 electrical degrees minimum conduction for each phase leg thyristor followed by a 60.degree. conduction of the neutral leg thyristors. In any event, the sum of the phase leg conduction and the neutral leg conductions is always equal to 120.degree. in a three phase system.

Abstract: A power conversion unit for supplying electrical power to a load from a polyphase a.c. source includes a controlled rectifier bridge connected between the source and the load. Control of the rectifiers is provided through the generation of a firing wave signal for each phase of the source which wave signals are phase displaced with respect to the phase-to-phase source voltages by a prescribed amount. Reference signals proportional to the desired output of the bridge and steering signals defining prescribed relationships between the firing wave signals are combined with the wave signals to generate signals utilized to control the conduction of the bridge rectifiers.

Abstract: A method and apparatus for correcting camber occurring during the rolling of a flat metal workpiece employs individual end adjustment of the work roll gap in response to the amount of camber detected.

Abstract: A system, for supplying electrical power from a source to a load, of the type employing phase controlled rectifiers for controlling the power from a polyphase source to the load includes circuitry to detect the existence of a rectifier which is conducting at an improper time and to provide appropriate corrective action to terminate such improper conduction.

Abstract: A method of controlling the shape of a workpiece in a rolling mill through the control of workpiece crown as the workpiece is being rolled includes the calculation of the roll-separating force required on each reducing pass as a function of roll elasticity, diameter and crown and workpiece resistance to deformation, width, entry crown and target crown.

Abstract: A constant horsepower drive system for a grinding wheel includes a first motor and associated control for rotating the wheel at a constant peripheral or surface speed and a second motor and associated control for providing linear relative motion between the wheel and a workpiece. Constant horsepower operation below the rated or base speed of the first motor is achieved by controlling the relative position of the wheel and the workpiece through the operation of the second motor. The control of the second motor is effected by the development of a correction signal which is a function of the quotient of a signal value representing the desired wheel surface speed divided by a second signal representing the counter electromotive force of the first motor.

Abstract: A method and apparatus for determining the initial opening of a pair of opposed work rolls utilized to reduce the thickness of a metal workpiece provides that selected readings of the roll separation force occasioned by passage of the workpiece through the rolls on a next preceding pass are utilized to determine the initial roll opening setting for the next pass of the workpiece between the rolls. The readings selected differ in accordance with a determination of whether or not the next pass is to employ automatic gage control.

Abstract: A friction hoist having at least two friction wheels each carrying a rope supporting a counterbalanced conveyance includes a motor to rotationally drive at least one of the wheels. The wheels are mounted for independent rotation on a common shaft and are permitted limited axial motion with respect to one another. A braking apparatus is provided for engagement with outer faces of the wheels while opposed inner faces of adjacent wheels are provided with a braking material such that actuation of the braking apparatus forces the wheels together and the wheels are braked as a unitary structure.

Abstract: A programmable data processor or controller serving as the main control in a control system contains an executive program for controlling the transfer of information between the processor and system equipment, updating that information during on-line control of the equipment and modifying the executive program to change operating parameters of the system while the data processor is controlling the system equipment. Modification of the executive program and displaying of system parameters related to the executive program and the system equipment is accomplished through the use of an operator's console which communicates with the data processor and system equipment as a result of operator intervention.