Abstract: A DC power supply having an input stage receiving input power at one voltage and an output stage connected to the input stage producing output power at another, output voltage. The output stage receives a control signal reducing the output voltage by a prescribed amount when the output current exceeds a given level. The control unit includes a comparator which compares the output current with a reference level and produces a current foldback signal if the output current exceeds the reference level.

Abstract: An induction heating apparatus comprising a static power converter operative to produce high-frequency power from low-frequency power and a heating unit to produce a time-varying magnetic field in response to the high-frequency power. The power converter includes a switching circuit and control means for triggering at high frequency during an incipient stage of operation of the apparatus and lower frequency varying according to the input power to the power converter and the load of the heating unit after the incipient stage.

Abstract: A d.c. power supply for use in microwave ovens in which an a.c. voltage having a commercial frequency is rectified and then is chopped at a high frequency by means of a switching element. The resultant voltage is smoothed before being applied to the microwave oven. The voltage level of the commercial frequency voltage is sensed to produce a control pulse the duty ratio of which becomes greater as the voltage level becomes lower. The control pulse is used to control the ON-OFF operation of the switching element. By this circuit configuration, the microwave oven is supplied with a continuously-controllable d.c. voltage having a flat waveform.

Abstract: In a DC/DC stabilized voltage converting unit having a series circuit including an input filter, a converter stage having a control input and an output filter, the improvement comprising: a control stage having an output connected to the control input; a voltage regulating circuit receptive of an output of the output filter and having an output applied to the control stage; an anti-overvoltage and anti-overcurrent stage receptive of an output of the converter stage and having an output applied to the control stage; a voltage converter chain coupling circuit for effecting the linking of units in a chain; an internal monitoring and commutating circuit connected between the voltage regulating circuit and the control stage for surveying the outputs of the converter stage; a visually and electrically signalling alarm circuit receptive of the outputs of the output filter and having the outputs thereof applied to the chain coupling circuit; and wherein the chain coupling circuit includes a first input for linking to

Abstract: Firing signals for the power switches in static power frequency changers are generated by comparing the integral of the output waveform ripple voltage to a repetitively generated stabilizing signal phase locked to, but having a time dependent magnitude independent of, the component waveforms of the output voltage. The stabilizing signal which changes in magnitude in one direction with time is reset to an initial level each time a firing signal is generated.

Abstract: A D.C. voltage apparatus providing isolated regulation. A D.C. voltage to be regulated is coupled through a D.C.-D.C. regulator and a D.C.-A.C. converter to the primary winding of a voltage transformer the secondary winding of which is then coupled to a rectifier and filter circuit. A feedback loop including a current transformer coupled to a rectifier and filter circuit and then through a resistive divider to a summer provides an error signal to the D.C.-D.C. regulator. The feedback loop injects into the summer a voltage which is opposite in phase to the output voltage of the D.C.-D.C. regulator which enhances the regulation capability of the device.

Abstract: Firing pulses to the thyristors in the nonload carrying bank of a naturally commutated power circuit of a static power converter are inhibited only after the current therethrough actually goes to zero. Where the thyristors are arranged in pulse groups, the firing pulses to each group are inhibited separately and in some instances not all groups in the nonload carrying bank are inhibited. Termination of current flow through a thyristor group is determined by comparing the group output voltage with a composite signal representative of the intended group voltage which is generated by summing selected portions of the source voltages applied to the group. Further firing of the thyristors in the group is inhibited only after the difference between these two signals exceeds a preset threshold value for an interval at least equal in duration to the thyristor reverse recovery time.

Abstract: A protected converter arrangement having electronic power circuitry using controlled valves and electronic information-processing control circuitry. The electronic power circuitry is provided only once, but the electronic information-processing circuitry is redundant and contains at least two complete control units. One unit leads and controls the electronic power circuit and at least one other unit operates in parallel, in standby condition. A monitoring device is associated with the control units and, in the event of a disturbance in the leading control unit, switches control of the electronic power circuit to an undisturbed control unit. The arrangement is especially suitable for use in protected converter arrangements which provide interruption-free supply of a load, having the advantage that the expensive electronic power circuitry is provided only once and is not operated in partial-load operation.

Abstract: A method for controlling a high-voltage direct current transmission system having a rectifier and an inverter of the controlled valve type, including the step of reducing the reference value of the current supplied from the rectifier to the inverter in a direct relationship to the value of the differencae between a predetermined value and the smallest of the margin angles of the inverter valves when the smallest of the margin angles of the inverter valves falls below the predetermined value, the current reference value being set above or equal to the minimum permissible value.

Abstract: In an arrangement in which a power source is required to supply energy to a load requiring at times more energy than can consistently be drawn from the source: the invention provides1. A charge control circuit which controls the charging of an energy store from a power source,2. A discharge control circuit which controls the amount of energy supplied to the load from the energy store and3. A processor which receives information concerning the state of the power supply and the energy store and which controls 1 and 2 above accordingly.

Abstract: An inverter system including a controlled direct current (d.c.) power source for providing a variable d.c. voltage to a variable output frequency inverter circuit by way of a suitable d.c. link, includes suitable circuitry for detecting a commutation fault or shoot-through condition within the inverter circuit and for taking appropriate remedial action to correct such condition. The shoot-through condition is determined as a function of the d.c. input current to the inverter circuit, the output alternating current (a.c.) of the inverter circuit and the extant condition of the load. In the particular embodiment of the invention illustrated, the load is an a.c. motor and the load condition sensed is whether the motor is in the running or idle mode of operation.

Abstract: A circuit means by which a high voltage, complex load may be precisely sensed and controlled. With high voltage AC loads, the effect of unavoidable stray capacitances is to render extremely difficult to measure and/or control that portion of total current which contributes actual power; that is, the resistive portion. Herein described is a circuit for rejecting all capacitive currents while measuring only the true resistive portion and deriving from the signal a filtered (averaged) voltage suitable for regulation and/or control. The circuit samples the total current only during the time when there is no capacitive current flowing. This sample is then compared with a reference, the difference amplified, and then averaged over many samples to derive a precise control signal.

Abstract: This invention relates to an improvement in a circuit arrangement for defined current sharing, between parallel-connected switching regulator modules in DC switching regulators with continuous inductor current and common error amplifiers for the purpose of generating regulated DC voltage from an unregulated voltage source, the improvement comprising means in each switching regulator module, composed of an inductor, a semi-conductor switch, a free-wheeling diode and a pulse-width modulator, whereby for the purpose of controlling the pulse-width modulator a signal proportional to the time-varying inductor current of the individual switching regulator module is negatively fed back to the output signal of the error amplifier, and where the signal resulting therefrom is used to control the pulse-width of the corresponding switching regulator module.

Abstract: In a power converter system wherein each thyristor of a three-phase full-wave bridge circuit having thyristors connected in all of bridge arms is fired for its controlling to thereby control the dc output voltage, when the dc output voltage is low, the firing angle of a group of thyristors on the negative side is fixed to a large value and the firing angle of a group of thyristors on the positive side is rendered variable within a small range so that a period may occur through which two thyristors connected in series in the full-wave bridge circuit are fired simultaneously. When the dc output voltage is high, the firing angles of groups of thyristors on both the positive and negative sides are made equal to each other and varied simultaneously. The system improves power factor and form factor over the entire controlling range of the dc output voltage.

Abstract: The method and apparatus of converting a sine-wave signal of one frequency to a sine-wave signal of a different frequency comprises a four port pass means that is controlled by at least two control signals. An error signal is generated by the difference between the rectified output signal and a locally generated reference signal. The error signal is compared to a high frequency sawtooth signal to provide a pulse width signal which generates a two state output signal. The first state is when the amplitude of the sawtooth signal is less than the error signal and the second state is when the amplitude of the sawtooth signal is greater than the amplitude of the error signal. The two state pulse width modulated signal is combined with the output from a polarity control means for obtaining the control signals.

Abstract: In a method and system for controlling high voltage direct current power transmission plants, the delay angle for the each converter is calculated directly by a calculating arrangement, which is provided for controlling all converters totally, from data set by an operator and data transmitted by suitable sending-receiving apparatus from each converter. Each converter receives the delay angle signal by suitable sending-receiving apparatus from the calculating arrangement and operates in accordance with the received delay angle value.The delay angle value is given the following equation. ##EQU1## where .alpha. is a delay angle value. E is either a measured or calculated A.C. voltage, and if it is a measured voltage, it is the voltage from an A.C. system to which each converter is connected, V is either a set or calculated D.C. voltage, I.sub.d is either a set or calculated D.C. current and X is a converter commutation reactance.

Abstract: An improved reactive power control for a static convertor wherein the improved control compensates for voltage transients caused by the connection and disconnection of reactance elements in an AC convertor network by making corresponding transient adjustments in a normal control angle of the convertor. A maximum angular increment in the direction of 90.degree. is applied to the normal control angle when the AC reactance switching occurs. If a capacitive reactance element is connected to the AC network, the maximum angular increment is rapidly built up after the connection and is thereafter gradually reduced. If the capacitive reactive element is disconnected from the AC network, the maximum angular increment is gradually built-up prior to the disconnection and after the disconnection the maximum angular increment is rapidly reduced. The sequence of incremental control angle build-up and reduction is reversed if the reactance element is a reactor.

Abstract: The DC to DC voltage converter consists of two single ended pulse width modulated converters with a single voltage control loop, a power balancing control loop and overload protection circuitry. The converters which share the same input and output filters are staggered in time so as to reduce the pulse current in the input filter capacitor and the ripple current in the output filter capacitor thereby permitting a reduction in the size of the input and output filters.

Abstract: The proposed digital device is intended to control a multiphase thyristor-pulse d.c. converter and comprises two decoders, each having as many main outputs as there are phases to that of the connector, and auxiliary outputs which alternate with the main outputs. The device further includes a clock pulse counter whose outputs are connected to inputs of the decoders, and a reversible counter whose add and subtract inputs are connected to outputs of a control unit, outputs of the reversible counter being connected to inputs of the second decoder. The device further includes a NOT gate and an OR gate having all of its inputs connected to an emergency output of a respective phase of the converter an output of said OR gate being connected to an input of the NOT gate.

Abstract: A two-stage commutation circuit for an inverter, each having a different energy storage capability, commutates the main semiconductor switches by creating a commutation pulse suitable for the different levels of load current. This improves overall inverter efficiency by decreasing the circulating commutation current at light loads due to reduced size of the commutation and makeup pulses utilized at the lower load current levels. The control circuit for the dual commutation circuits includes a voltage detector for sensing the level of the DC input voltage and current detectors for sensing the times at which the load current is essentially zero so that the transistion between the commutation circuits will occur without perturbations in the cyclic operation of the inverter.

Abstract: An alternating current input to direct current output power supply providing a regulated constant voltage output or constant current output and incorporating a switching-mode regulating element. Regulation is primarily obtained by means of a bi-directional switching element operated at a relatively low voltage, and the alternating current voltage output from the switching element and an associated power transformer is applied to a rectifying voltage multiplier to produce a high voltage output. The voltage multiplier is subject to receiving an unbalanced potential, thereby imposing a dc off-set potential onto the switching element to cause instability in the potential at the power supply output. A correcting circuit is provided to eliminate the effect of the dc off-set potential on the switching element.

Abstract: Apparatus for direct current to alternating current power conversion by means of progressive variation of magnetic flux in associated magnetic paths. A direct current input is subdivided into power pulses in two permeance controlled transformers. The pulses are modified, stabilized and recombined in phase opposition to produce a single alternating current output.

Abstract: The invention relates to an inverter circuit for operating an asynchronous motor having an adjustable speed. The inverter has its output frequency regulatable by a frequency regulator and the D.C. supply has its voltage regulatable by a voltage regulator. There is a desired value frequency regulator having a signal (f) and voltage and current measuring devices having output signals (E) and (I). A control circuit processes these signals (f, E, I) to form input values for the referred to voltage and frequency regulators. The control circuit includes a computer circuit which, from at least two output values and at least one constant, calculates a computed value of the third output value which, together with the first-mentioned output values, given by way of computation a substantially constant slip frequency for a given desired value, and this computed value is compared with a value substantially corresponding to the actual third output value.

Abstract: A system for extracting and converting into complex power the electrical energy conveyed through a high voltage direct current (HVDC) transmission line, the system being serially mounted along that transmission line. The system comprises converter bridges to convert the transmission line high voltage into AC active power and a unit, connected to the line, for generating reactive power and feeding the latter through both the converter bridges and the load mounted across the system output. Moreover, there is provided a device for controlling the rate of extraction and conversion of the HVDC energy in function of the active power supplied by the generating unit. This control device ensures that the load requirements in active power are entirely supplied by the converter bridges alone. A voltage regulator is associated to the generating unit for the purpose of keeping constant the output voltages of that generating unit, thereby causing a nul output active power from the unit, in steady state.

Abstract: Power supply having means for developing a voltage overload signal representing a current overload condition in the power supply and then reducing the output current from the power supply as a result of the voltage overload signal. The voltage overload signal is applied to a servo or error amplifier to cause the error signal therefrom to change in a manner to reduce the power supply output voltage which in turn is fedback to the said amplifier to cause output current foldback.

Abstract: An apparatus for controlling the operation of an inverter which converts DC power obtained by rectification of a received AC power or DC power received from a battery which is alternatively actuated in case of an AC power supply failure or the like, into AC power. The inverter control apparatus includes a first control means which detects the output voltage of the inverter to thereby control the operation of the inverter in accordance with the detected value of the inverter output voltage. The inverter control apparatus further includes a detector for detecting variations in the input voltage of the inverter and second control means for controlling the width of the firing angle which is controlled by the first control means, in accordance with the detected value of the inverter input voltage variations, so that variations in the output voltage of the inverter may be suppressed even in the case of occurrence of variations in the input voltage of the inverter.

Abstract: A power circuit for use in billet heating, surface heat treating and melting and protective circuitry associated therewith. The power circuit generally comprises a source of potential in series with a pair of inductances and an inverter module. The inverter module has two sections each comprised of a thyristor in parallel with a diode. A pair of series connected charging capacitors are connected across the source of potential and a load is connected from between the capacitors to between the two sections of the inverter module. Current flows through one thyristor, through the load and charges the capacitors. The capacitors discharge and a reverse current flows through the load and through the corresponding diode. This cycle is repeated then with the opposite section of the inverter module. A commutation failure protection circuit is provided which detects the voltage collapse condition accompanying a short circuit through the inverter module and when this occurs, it acts to shut off the thyristors.

Abstract: A circuit for shutting down an inverter that includes at least a series combination of first and second gate controlled rectifiers and a load. The circuit is comprised of means for sensing the direction and magnitude of the instantaneous current flowing through the load, and means responsive to the direction and magnitude of the sensed current for generating an output signal when the magnitude of the current exceeds a predetermined threshold level and the current is flowing in a first direction. The circuit further comprises means responsive to the simultaneous receiving of a shutdown signal and the generated output signal for further generating a gating pulse to be applied to the second gate controlled rectifier to cause the current flowing through the load to quickly extinguish. Further included is means responsive to the shutdown signal for inhibiting further regular gating of the gate controlled rectifiers to ensure quick turn off of the inverter.

Abstract: An HVDC electric power delivery system having a floating current order current control subsystem is described. The system is comprised by power converters at each end of an HVDC power conductor link each of which includes a plurality of controllable electric valves connected between alternating current and the direct current electric power conductors together with means for cyclically firing the valves in a predetermined sequence and at firing angles measured with respect to the alternating voltage that can be varied to control the flow of power between the alternating current system and the direct current system. Each of the power converters further includes a regulator for comparing a plurality of input control signals which respectively represent different predetermined operating characteristics of the HVDC system during operation and for deriving an output error control signal that controls the firing angles of the valves.

Abstract: A display and power supply system in which the power supply uses a switching frequency which is higher than the highest linear deflection rate used in a cathode ray tube display device supplied by the power supply and in which the frequency of the power supply and the information repetitively displayed on the display are synchronized to eliminate interference of the power supply frequency with the display characteristics.

Abstract: In a convertor plant for connection between a DC network and an AC network which includes at least one convertor group formed of two convertors with AC terminals for connection to the AC network and DC terminals for connection to the DC network, a reactor is connected on the DC side of one of the convertors and switches are provided for alternatively connecting the DC terminals of the convertor to the DC network in parallel with the other convertor or for connecting the reactor between the DC terminals of the convertor. Preferably the plant includes two or more convertor groups, each of which is provided with a transformer for connection to the AC network, and the transformers have different circuit angles for increasing the resulting pulse number of the plant.

Abstract: A switching type power supply is provided which includes a first and a second SCR with a diode connected in reverse across each of them. The first SCR-diode pair in response to a clock pulse charges a capacitor which when fully charged causes the first SCR current to return to zero, forward biases the first diode and commutates the first SCR off for at least the required minimum turn-off time of the SCR. After the capacitor reaches the peak charge value, the second SCR is selectively triggered to couple the desired portion of the stored energy to the power supply load via a transformer. After the currents in the secondary windings of the transformer reverse, and the capacitor achieves a peak charge of the opposite polarity, the current through the second SCR becomes zero, the second diode is forward biased, and the second SCR is commutated off.

Abstract: A method and apparatus for determining the commutating and protection time in the operation of a load controlled inverter, particularly of a parallel resonant circuit frequency converter, in which the firing instant of the thyristors prior to the zero crossing of the resonant circuit voltage is derived from the intersection point of two measured voltages, one proportional to the resonant circuit voltage and the other including the sum of two voltages, one of which leads the resonant circuit voltage by 90.degree. and is proportional to the product of the resonant circuit frequency and the first measured voltage, and the other of which is proportional to the inverter output current, permitting the current dependent commutating time along with the constant protection time to be unequivocally determined.