Abstract: An A.C. to D.C. power conditioner, which draws sinusoidal input current utilizes digital proportional-integral control to provide output voltage regulation by adjusting the gain of a current program loop. The current program loop controls the state of a power switch to force the instantaneous average current in an inductor to follow the instantaneous rectified line voltage. Variable hysteresis control provides noise immunity by increasing the ripple current in an iron-cored filter inductor when the instantaneous input voltage is high. Digital proportional-integral (PI) control provides output voltage regulation by adjusting, in discrete steps, the gain of the current program loop. A multiplying digital-to-analog converter serves as an interface between the voltage regulation loop and the current program loop. The sampling rate of the PI controller is determined by the input line frequency, which allows good transient response to be obtained.

Abstract: Alternating current electric power fed to a load is controlled to a target value using phase control. During a half cycle of the alternating current waveform, sampling of voltage and square calculation of the sampled value are repeated. During the remaining half cycle, average value calculation based on the result of the above calculation, root calculation and proportional calculation are implemented. Thus, the power control cycle is completed within one cycle of the alternating current waveform. By utilizing a plurality of sampling data, dropped data locating in a non-sampling period therebetween is obtained by interpolation. Sampling starts in synchronism with the energizing start-up phase.

Abstract: A device is described for the generation of drive signals for thyristors or power transistors in circuits for the energy supply of apparatuses and installations with regulated and/or adjustable direct voltages or direct currents. In systems with a master or controlling computer there serves as desired value giver a digital memory, which makes available the calculated desired values as a binary number on its output, while as actual-value giver there serves a binary counter which counts the beat impulses of the computer, in which system a comparison circuit on equality of the numbers triggers an impulse the time beginning of which corresponds to the ingate angle or its duration to the impulse width of a pulse-width modulated signal.

Abstract: In an electrostatic precipitator system powered by a primary power source, the power supply has a converter and a high voltage device. The converter can be coupled to the primary power source for producing a converter voltage with a different frequency content. The high voltage device is driven by the converter, producing from its converted voltage a high voltage. This high voltage is influenced by the different frequency content, having at least one frequency component at a predetermined low frequency which is sized to promote efficient precipitation.

Abstract: An arc welder is provided with a phase control circuit by rectifying elements to simplify the construction of the arc welder and improve the performance and operability. The arc welder is further provided with a storage control circuit to enable the retrieval of stored data of the same welding conditions. A union/individual control circuit is provided to eliminate troublesome adjustment of potentiometers.

Abstract: A circuit for generating control signals used in detecting a power failure in an uninterruptible power supply in which the A.C. signals of the power supply are examined to output a first signal representing the zero crossing of the A.C. signals. This first signal is used to reset an oscillator whose output clock signals are synchronized with the frequency of the A.C. signals by a phase lock loop circuit. The clock output of the phase lock loop circuit operates a counter whose output count is used to address a programmable read-only memory which outputs binary bits to a digital-to-analog converter which in turn outputs a full wave rectified sine wave operating at the system frequency which is used as a reference to detect the occurrence of a power failure in the main source of A.C. power signals. A second control signal is generated indicating a power failure condition which is used in switching an inverter into the power supply for supplying A.C. signals to a load.

Abstract: This apparatus can limit the power by limiting the duty cycle of current carried by a pair of lines. These lines intermittently conduct electrical power. A clock can provide a periodic timing signal. This clock is resettable to change the phasing of the timing signal. A switch serially coupled to at least one of the lines can periodically interrupt current of the lines with a period proportional to the period of the periodic timing signal. A resetter coupled to at least one of the lines can reset the clock in response to the average magnitude of voltage across the lines increasing by a predetermined extent.

Abstract: This apparatus can apply electrical power to a supply terminal from a pair of lines having a variable current and voltage. The apparatus has a voltage tapper and a series device. The voltage tapper is coupled to the lines and to the terminal for applying to the latter power drawn from the lines when their voltage difference exceeds a predetermined value. The series device is serially coupled into a given one of the lines for producing a voltage drop. The series device is coupled to the supply terminal for supplying power thereto as a predetermined function of the voltage drop of the series device.

Abstract: Apparatus can limit power by limiting the duty cycle of current carried by a pair of lines. The lines intermittently conduct electrical power. The apparatus has a clock, a converter and a switch system. The clock can provide a timing signal. The converter is driven by the lines and can convert its intermittent electrical signals to uninterrupted power and can supply this uninterrupted power to the clock. The switch system responds to the timing signal and can periodically interrupt at least one of the lines.

Abstract: A system for controlling the voltage of an electrofilter of the type which, after a voltage breakdown, substantially reduces the magnitude of the electrofilter voltage. After a predetermined deionization time, the filter voltage is raised to a new level which is lower than the filter voltage at which the initial voltage breakdown occurred, by a predetermined amount. The filter voltage is subsequently raised in accordance with a predetermined voltage-time function until a further voltage breakdown occurs. The electrofilter voltage is controlled by a microcomputer system in accordance with stored control parameter values. The stored control parameter values are advantageously recalled to control the electrofilter voltage in response to the operating state of a plant in which the electrofilter is employed.

Abstract: A method for operating an electrostatic precipitator with a DC voltage and superimposed pulses or superimposed AC voltage in which individual parameters such as amplitudes, pulse repetition frequency, pulse width, etc. are iteratively and continuously varied in such a manner that the sum of the pulse and the DC voltage power approaches a minimum. A computer which calculates, from the dust load and the absorbed electric energies of the filter, control commands for the DC and pulse voltage source is used for this purpose.

Abstract: A back corona detector that reduces current flow to the plates of an electrostatic precipitator when a corona occurs between a plate and the dust layer that forms on the plate thereby minimizing the corona condition. The ramping voltage in a transformer/rectifier set under usual operating conditions will vary proportionally with current flow. At the onset of a back corona condition, a comparator senses a sudden increase in current with respect to the voltage indicating that the current is being consumed to maintain the corona rather than providing for particulate precipitation. A current set-back circuit is then pulsed periodically so that the current is continuously reduced until the voltage/current relationship is maintained at the knee of the voltage/current curve.

Abstract: Disclosed is a method and circuit for automatically adjusting the firing angle of a switching element, such as a thyristor or triac, to minimize surge currents produced in reactive loads in AC power applications. A typical application would be in a microwave oven controller when the circuit would be used as an interface between the microwave oven control circuitry and the thyristor driving a magnetron. The circuit is comprised of a digital-control, phase-locked loop oscillator which produces a series of triggering pulses which are synchronized with the AC line voltage; the oscillator oscillates at a known frequency and clocks a counter during one half-cycle of the line voltage, resetting the counter during the opposite half-cycle. A peak fire detection circuit is coupled to the oscillator. An enable signal is generated by the microwave oven control circuitry. Since the oscillator frequency is known, the AC line voltage peak occurs at a known state of the counter.

Abstract: A voltage control system for an induction motor, consisting of a SCR AC voltage controller with sensing and control circuitry, adjusts the motor voltage in response to the load torque demand, thereby minimizing the motor's magnetizing current and its associated losses. The motor displacement power factor angle, which is responsive to load torque, is sensed by directly sensing the motor voltage, deriving its fundamental or line frequency component, and phase-comparing that component with a similiarly derived fundamental component of the motor current. The resulting displacement power factor signal is amplified, together with a stability augmentation signal, to form a phase delay command signal for the AC controller. The stability augmentation signal, representative of the blocking voltage across the AC controller SCRs, is formed by rectifying the 180 Hz single phase sum of the three motor voltage signals.

Abstract: The automatic recording of the current-voltage characteristic of an electrostatic filter in which the characteristic obtained upon stepwise variation of the control is displayed to the operating personnel and at the same time saturation phenomena and voltage maxima are picked up.

Abstract: A method for controlling the voltage of an electrostatic filter at the breakdown limit in which, when a breakdown occurs, the voltage is reduced by an amount which is determined by the breakdown voltage and the prior history of the breakdown and the waiting time to the next increase of the filter voltage is made dependent on the ratio of the voltages at successive breakdowns by comparing voltage amplitudes which immediately precede the breakdowns.

Abstract: A trigger system and method for use in a line commutated power converter as used in either a rectification or an inversion mode of operation and more particularly a trigger system and method for a static converter for accurately controlling the firing angles for controlled rectifiers for converting between multiphase a-c power and d-c power by use of digital signal having magnitudes which are varied for varying firing angles for providing a converted output having a regulated voltage and/or current.

Abstract: A digital control system for controlling firing pulses supplied to thyristors for power conversion to desired phases, wherein data necessary for obtaining desired phase control signals is set in a counter which normally counts clock pulses having a predetermined period and the firing pulses are generated in synchronism with the generation of overflow pulses from the counter. The data setting to the counter, which is repeated at a period shorter than that of the source voltage, is performed by reading out the actual count value of the counter by a digital arithmetic processor circuit, by correcting the read value by the use of the value corresponding to a desired phase and by setting the corrected value again in the counter.

Abstract: A digital control unit for a static converter contains a binary-coded counter which counts the pulses of an oscillator. The counter outputs are connected to the address inputs of a function memory in which sawtooth or ramp functions are stored. The numbers read out of the function memory are compared in a comparator, with a number determining the drive of the static converter. The result of the comparison and pulses on selected outputs of the counter are linked, in a logic circuit, to form firing pulses for the static converter. The invention is suitable for control units for static converters, in particular for AC control elements and inverters. All expense of adjusting, and all compensation of drift errors is obviated.

Abstract: Induction heating apparatus using gate-controlled switching devices includes a zero crossing point detector for detecting the occurrence of each zero crossing point of high frequency energization current, and a timing circuit which provides timing action in response to the detected zero crossing point. The timing action is controlled by a power control circuit which detects the level of energy delivered to a load within a range from the inherent turn-off time of the gate-controlled switching devices to a desired value.

Abstract: A regulated power supply circuit includes a transformer having a primary winding and a secondary winding electromagnetically coupled by an iron core. A source of AC operating voltage is coupled to the primary winding of the transformer via an actuable switch means. A load circuit coupled to the secondary winding circuit is adapted to be energized by a voltage developed in the secondary winding circuit. Means are provided for sensing the polarity of each half cycle of said source of AC operating voltage. Memory means are coupled to the transformer for providing information representative of the polarity of each half cycle of the source of operating voltage applied to the primary winding of the transformer. The memory means are operable to maintain the information for a period of time when the switch is actuated to be opened. Means are also provided for sensing a parameter in the secondary winding circuit related to the energy available in the secondary winding circuit.

Abstract: Disclosed is a phase detecting circuit having first and second sets of two-phase sine wave signals each set of which has phases different from each other by 90.degree., an arithmetic operation circuit for detecting a phase difference between the two-phase sine wave signals, and a frequency variable signal generating circuit for producing an output pulse with a frequency varying in accordance with the sum of proportional and integrated values of an output signal from the arithmetic operation circuit. The phases of the sine wave signals are so changed as to minimize the phase difference. The phase detecting circuit is provided with a function generating circuit which counts the output pulses from the frequency variable signal generating circuit and produces the second set of two-phase sine wave signals with phases different from each other by 90.degree. whose phases are changed on the basis of the count data.

Abstract: There is provided a precipitator system including a voltage controller which produces from an alternating power source a variable output. This variable output drives a high voltage converter which applies a high voltage to a precipitator. This variable output is controlled by a control signal from a command subsystem. Preferably, the command subsystem is operative to repress the drive to the high voltage converter in response to its loading exceeding a predetermined limit during a corresponding limit interval. After this limit interval, the command subsystem is operative to rapidly restore productive drive to the high voltage converter, preferably by the next half cycle of the power source that has a polarity opposite to that existing at the beginning of the limit interval. In this fashion stablized operation is quickly achieved. Also included, preferably, is a conductive element that is coupled to the high voltage converter.

Abstract: In a method and system of controlling the effective value of alternating current supplied to a load through controlled semiconductor switching elements which are connected in parallel opposition, circuits are provided to produce data ##EQU1## where .DELTA.I represents an increment of the load current, .DELTA..alpha. an increment of the ignition angle .alpha. and I.sub.90 the effective value of the load current at an ignition angle of 90.degree.. .DELTA..alpha. is calculated according to an equation ##EQU2## where K is a constant smaller than 1. Then .DELTA..alpha. is added to an ignition angle .alpha..sub.1 in a preceding half cycle to determine a new ignition angle which is used to control the controlled semiconductor switching elements.

Abstract: In a method and apparatus for controlling an AC power supply from a power source to a load having a considerably large inductance through electric valve means, the ignition phase angle of the valve means is limited to a value greater than the angle of the power factor. The limiting value is calculated for each cycle based on the power source voltage and a turn-off period of the valve means in the cycle immediately preceding the aforementioned cycle.According to this invention, it is possible to automatically control the ignition of the electric valves over the entire cycle.

Abstract: A solid-state circuit breaker is provided with circuitry for permitting off/on/reset operations actuated by a mechanical toggle control switch for close simulation of magnetic circuit breaker operation. A power continuity feature is provided for load power by locating the control switch so that it opens all of the circuit, except the static power switch branch, between the source and the load, to provide a high degree of fail-safe protection for the apparatus. The power continuity feature includes means for zero crossover synchronization both upon power-up and power-down conditions. A circuit lockout feature is used so that on power-up or turn-on, operation is delayed until the occurrence of an internal power-ready condition. On power-down or turn-off, there is means for circuit retention subsequent to switch opening and internal power removal in order to accomplish load turn-off at a desired zero crossover point of the load power through the power switch.

Abstract: A solid state circuit breaker is provided with circuitry for permitting off/on/reset operations actuated by mechanical toggle switch for close simulation of magnetic circuit breaker operation in three phase or other multiphase systems. A power continuity feature is provided for load power by locating the control switch so that it opens all of the circuit except the static power switch branch. The control switch is located between two of the supply voltage phases and the power supply for the control circuitry. The correct zero crossover of one phase is utilized to produce turn-on at zero degrees of that one phase while the other two phases are respectively at minus 120.degree. and plus 120.degree. without any significant impairment of overall circuit breaker performance. An overcurrent protection system is included that uses optical isolators with reduced sensing voltages developed directly from terminals of the power switch elements.