The Babcock & Wilcox Company

John W Robertson, Jr

Edward Bastijanic

Gordon D Woolbert

Scotty Y Jewett

John J Fry

Edward L Sterling, Jr

Jane E Smith

James M Smith

David J Wroblewski

Stuart B Siegel

An overcurrent protection system for AC motor control systems which provides a separate overcurrent shut down mechanism for each phase of the AC power used in an AC motor. These separate phase shutdown mechanisms provide protection for minor overcurrent conditions without shutting down the entire motor control system. The overcurrent protection system also provides a mechanical feedback apparatus for totally shutting down the motor control system only in a severe overcurrent condition.

Current fault detection system and method for AC controller

An automatic calibration and control system for a combined oxygen and combustibles analyzer comprises a process control computer which automatically calibrates a combined oxygen and combustibles analyzer. The computer initiates a calibration sequence through a mechanical unit which introduces calibration gases to the analyzer. The computer calculates a drift adjustment for both oxygen and combustibles and applies it to the incoming oxygen and combustibles signal from the analyzer to arrive at calibrated oxygen and combustibles signals. The system allows both oxygen and combustibles signals to be calibrated automatically and concurrently with minimal operator interface.

Automatic calibration and control system for a combined oxygen and

A safety control system for a coal pulverizing mill is disclosed. The control system utilizes measurements of the net oxygen level and the carbon monoxide equivalent (CO.sub.e) level of the combustible gases within the pulverizing mill. First levels of the net oxygen and the rate of carbon monoxide equivalent change in the pulverizing mill are utilized in a control logic system to actuate alarms. Second levels of the net oxygen and the carbon monoxide equivalent (CO.sub.e) level in the pulverizing mill are utilized to accomplish the inerting of the mill.

Apparatus for monitoring low-level combustibles

Apparatus for monitoring low level combustibles

An improved power supply for power switches arranged in a totem pole configuration is disclosed. A single power supply, having an output voltage substantially less than the voltage applied to the upper power switch, periodically charges a capacitor within a flying capacitor circuit. Microprocessor based control circuitry controls the charging and discharging of the capacitor and the periodic operation of the power switches resulting in the voltage at the output of the power switches being at system common or at the voltage applied to the upper power switch.

Power supply for totem pole power switches

An electronic integrator for integrating a linear voltage signal utilizes a voltage-to-frequency converter for converting the voltage to input frequency. A binary counter counts pulses of the input frequency. The binary counter generates a first operating frequency which is applied to a scaling circuit and another calibration frequency which has a much higher rate than the operating frequency. Both, however are proportional to the input frequency. The scaling circuit scales the operating frequency to a selected extent to form a counting signal. Using the double pole switch, either the calibration frequency or the counting frequency are applied to a pulse counter which is either used to integrate the input voltage signal by counting up pulses of the scaled counting signal, or the integrator can be calibrated using the calibration frequency which quickly increments the pulse counter.

Electro-mechanical integrator

A pressure transmitter assembly comprises a pressure transducer having a pair of inputs each connected to a separate pressure line. A valve is connected in each pressure line. A pressure equalizing line is connected between the pressure lines at a point between the valves and the pressure transducer. The pressure equalization line is provided with an equalization valve. All three valves are connected to a switching circuit which is controlled by a microprocessor. The switching circuit functions to open both of the valves in the pressure lines while closing the equalizing valves so that the pressure transducer is exposed to two separate pressure and generates a signal corresponding to a difference in two separate pressures. To zero the transducer and recalibrate the transmitter, the low pressure line valve is closed while the equalizing valve is opened. This equalizes the pressure between the two pressure lines so that any signal from the transducer corresponds to a zero pressure difference value.

Self-zeroing pressure transmitter with automatic pressure manifold

Programmed digital equipment is utilized to generate three-phase pulse width modulated waveforms that are used in controlling an induction motor. A microprocessor is programmed to initialize conditions in the system, to perform a main task including the storage of converted analog signal, the checking of limits of motor motion and information fed back from the motor concernings its position, and the ramping of frequencies to change the position of the motor. A memory is provided for the programming which memory also contains tables that correspond to 90.degree. of each desired wave form. A single 90.degree. segment of each wave form is needed to generate all parts of each of the three phases. An analog to digital converter is utilized to convert analog information concerning gain, set point, dead band and feedback signal into digital signals which are stored and processed by the microprocessor. Programmable timers are connected to the microprocessors for generating the wave forms and for supplying master timing and interrupt signals indicative of an undesirable condition in the motor control.

Digital generation of 3-phase PWM waveforms for variable speed control

A resistive network is used for an electro-pneumatic converter so that the speed of the electro-pneumatic converter can be regulated. The converter includes a reversible DC servo motor having a pair of terminals connected to a pair of lines. The lines are selectively connectable to a common terminal of a power supply. The power terminal of the power supply is connected over a variable resistor to a terminal connecting the lines. Selectively connecting one of the lines to the common terminal causes electrical power to pass through the motor and one for an opposite direction to turn the motor shaft in a selected direction of rotation. The speed of rotation is determined by the position of the variable resistor. The motor shaft is used in conjunction with a cam that is associated with a nozzle supplied with pressurized gas over a bellows. The nozzle is moved closer or further away from the cam edge as the bellows expands or contracts. A line connected upstream of the bellows provides gas at a selected pressure which is porportional to the position of the cam. The position of the cam is determined by the rotation of the motor shaft.

Variable speed resistive network for a pneumatic servo assembly of an

A controller for an induction motor used as a servo positioner comprises a position control module including a microprocessor with memory for generating a plurality of pulse width modulated waveforms. The module includes an analog to digital converter for converting one of four analog signals into digital signals readable by the microprocessor. The analog signals correspond to a gain signal, a feedback signal, a set point signal and a dead band signal. The module also receives digital signals for programming purposes. The microprocessor is programmed to initialize conditions and convert the analog signals. The module is included in a three phase drive controller which has drivers connected to the module for receiving the waveforms and generating corresponding AC inputs to the three phase motor. An overcurrent detector is provided for sensing overcurrents in the AC signals and for generating an interrupt signal which is applied to the module for interrupting the function thereof. The module according to its programming can be placed in one of three modes for interface with a broad spectrum of automatic control systems. The modes include automatic-analog, automatic-pulse, and closed-contact controls.

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Chesterland, OH, United States of America

John W Robertson, Jr