Abstract: A hybrid phase-controlled rectifying bridge includes both controlled and uncontrolled electric valves referred to as thyristors and diodes, respectively. Each of a pair of thyristors is periodically fired at an "angle" that can be advanced or retarded as desired, whereupon load current commutates to the thyristor from the corresponding diode. Subsequently the thyristor is turned off at a desired extinction angle by the action of cyclically operative forced commutation means. To avoid reverse recovery overvoltages across a diode when the desired extinction angle is only slightly larger than the firing angle, means is provided for temporarily preventing any turnoff action during the diode-to-thyristor commutation interval and for an additional interval that gives the diode sufficient time to fully recover its reverse blocking capability.

Abstract: In a protective circuit for the thyristors of an inverter circuit in a rail-bound vehicle, RC-R members are connected in parallel with the individual thyristors in order to prevent undue reverse voltages and a fuse is provided to cut off excess currents.In order to reduce the dimensions of the thyristors the series connection of a resistor and a decoupling blocking diode is connected in parallel with each thyristor. The respective center points of these components are connected, via a breakdown diode, with the control grid of the respective thyristor, so that the secondary voltage of the inverter circuit is reduced when there is a malfunction due to excess reverse voltage and the inverter circuit is disconnected from the rail-road mains.

Abstract: A phase-controlled ac-to-dc rectifying circuit includes a pair of alternately conducting main controllable electric valves and cyclically operative forced commutation means for turning off the main valves. The forced commutation means comprises a pair of auxiliary controlled rectifiers respectively connected, in circuit with a commutating capacitor, across the main valves, and the auxiliary rectifiers are alternately turned on in response to periodic trigger signals that are normally produced by associated control means. Protective means is provided for inhibiting the trigger signals when the magnitude of voltage across the commutating capacitor is lower than a critical level which depends on the magnitude of the current being conducted by the main valves, thereby avoiding a risk of commutation failure due to low capacitor voltage.

Abstract: The invention relates to a device particularly adapted for use with the power supply of a computer for controlling the regulating facilities in an electric high-power AC-DC converter of the power supply.This control device (D) comprises a regulation (CC) control comparator connected to the storage facilities (S) of the converter and receiving a reference voltage having a "nominal" value when the converter is normally powered by an AC network and receiving a portion of the output voltage from the converter, the output of said control comparator (CC) supplying an error signal to the regulating facilities (MR) of the converter. The control device also includes facilities (R) for supplying a variable reference voltage to the control comparator (CC) so that at the moment of recovery of the network following a cutoff, the voltage at the input of the filtering facilities (F) of the converter is, at the most, equal to the output voltage of the storage facilities (S).

Abstract: A power converting device including at least one power converting element, and a protection circuit monitoring the switching characteristics of the power converting element and for protecting the power converting element during switching thereof, including a first circuit coupled to detect a reverse voltage applied to the power converting element, a second circuit coupled to the first circuit for receiving the detected reverse voltage and for integrating the detected reverse voltage to produce a reverse voltage/time integral signal, and a third circuit coupled to receive the reverse voltage/time integral signal for producing a decision signal only when the amplitude of the reverse voltage/time integral signal exceeds a first prescribed value, the decision signal indicates that the power converting element is extinguished.

Abstract: The proposed method consists in that a narrow control pulse is applied to the thyristors of the arrangement at the beginning of the conduction interval of the arrangement. The positive voltage across the monitored thyristors is measured and a monitor signal is formed at the point in time when the voltage reaches a preset level. Using the received monitor signals, one can count the number of the thyristors whose positive voltage exceeds a preset level. At the point in time when the number of the monitor signals reaches a preset value, additional narrow control pulses are applied to the thyristors.The proposed control system comprises devices for measuring the positive voltage across the monitored thyristors and an adder connected to the devices. The adder and a reference signal source are coupled to a comparison circuit which, like a sync pulse source, is connected to an AND gate. The AND gate and the sync pulse source are connected to an OR gate which couples an amplifier-former connected to the arrangement.

Abstract: A rectifier controller for controlling bridge connected silicon control rectifiers (SCRs) (1 to 6) of a three-phase rectifier which is used to supply a direct current (DC) voltage to an inverter (314) used for injecting pulse coded audio frequency signals on a power line. The controller supplies gate control signals to the SCRs (1 to 6) of the rectifier bridge in accordance with the envelope of the three-phase supply voltages and provides for protection of the inverter (314) when shoot-through conditions occur in the inverter (314) and provides for output DC voltage adjustment by controlling the firing time of the rectifier bridge SCRs.

Abstract: An arrester is provided including series connected first and second nonlinear resistance elements and a by-pass circuit. The by-pass circuit is connected in parallel with the second nonlinear resistance element and short-circuits the second nonlinear resistance element only when a voltage of a predetermined polarity is applied to the second nonlinear resistance element. An semiconductor circuit arrangement with a protection device is also provided, where the arrester is used for protecting a semiconductor device.

Abstract: A dc motor driving apparatus comprising a full-wave rectifier bridge circuit for supplying dc power to a dc motor and a dc motor driving control circuit for controlling the turning on and off of thyristors forming the full-wave rectifier bridge circuit, further comprises a protecting control circuit operatively associated with the dc motor driving control circuit for preventing the occurrence of a short-circuit mode in the full-wave rectifier bridge circuit caused by a malfunction of the thyristors and ensuring highly efficient, quick responsive and stable control of the reversing, braking, stopping and other speed changing operations of the dc motor.

Abstract: An apparatus for preventing malfunctions in a phase control mechanism of the type in which the firing angle of thyristors in a thyristor bridge is controlled to regulate the rotational speed of a DC motor comprising the load of the thyristor bridge. Thyristor firing pulses are produced each time a rising analog speed command signal generated in response to the phases of a N-phase power supply intersects N-number of sawtooth signals. Immediately after the generation of each firing pulse, the thyristors are not supplied with firing pulses for a time interval at least equivalent to the thyristor commutation overlap time.

Abstract: An overvoltage protection circuit for a circuit array including one or more semiconductor devices such as thyristors derives its energization solely from the voltage across the array. A unidirectional current is developed to respond to that voltage and this current is utilized to develop an electrical charge of not more than a predetermined magnitude. The unidirectional current is also utilized to develop a signal which is proportional to the voltage across the array. When this signal reaches a predetermined level, indicative of an overvoltage condition of the array, a switching current is rendered operative to cause the stored charge to be applied to the gating electrodes of the array semiconductor devices to thereby render each such device conductive.

Abstract: A failure detector is provided for detecting unidirectional failures in triacs, particularly as used in power factor controllers for induction motors. In a first embodiment, the triac voltage waveform is sensed and upon detection of an unbalanced signal, corresponding to failure of the triac in either the positive or negative direction, the triac is turned full on in both directions. In a second embodiment, a pair of pulsed signals are derived, the pulse durations of which are proportional to the phase difference between the load current and voltage for each half cycle, and the triac is turned full on responsive to a difference in pulse duration between the half cycle signals. An unidirectional open circuit detector is adapted to use a signal from either of the first and second embodiments to turn the triac off in response to an open circuit failure in either direction.

Abstract: There is provided by this invention a static VAR generator having an auxiliary shutdown firing pulse generator that initiates a thyristor controlled inductive current to cancel only capacitive current supplied by the static VAR generator in the event of failure of the VAR generator's control means monitoring the capacitive current requirements.

Abstract: There is provided by this invention a static VAR generator having an auxiliary shutdown firing pulse generator that initiates a thyristor controlled inductive current to cancel any capacitive current supplied by the static VAR generator in the event of failure of the VAR generator's control means monitoring the capacitive current requirements.

Abstract: Voltage and current supplied to the primary winding of the transformer-rectifier (T-R) set of an electrostatic precipitator via silicon-controlled rectifiers and a reactor are automatically controlled by sensing spit and spark discharges within the precipitator and the phase shift which occurs between line voltage and line current (usually referred to herein as primary current) when precipitator voltage drops to a low value, as caused by a heavy spark or arc. Signals are developed therefrom which are used to control precipitator voltage through phase control of the SCR's. An arc is extinguished at the end of the current one-half cycle in which it starts. An inhibit circuit is provided for preventing detectable transients caused by SCR turn on from falsely triggering the automatic control system thereby permitting increased sensitivity in the spit sensing circuit.

Abstract: In power conversion apparatus such as a naturally commutated cycloconverter for use in converting the output of a variable speed generator to a constant frequency, there is provided an end stop control circuit for ensuring commutation of power switching devices that includes timing wave generators for both rectification and inversion end stops. The timing wave generators are phase locked with the generator outputs but are controllable by end stop bias signal derived from a variable system parameter that may be independent of the source, such as load current to provide prompt protection against converter malfunctions due to excess load currents.Further provided is an excess current detector employing, for each phase, a pair of high slew rate, high current unipolar output op amps connected in a voltage follower configuration with a common pull-up resistor and a common load capacitor to develop a peak current signal representing the greater of the positive and negative peaks of the alternating phase current.

Abstract: A failure detection device for a convertor which converts alternating current into a direct current through a plurality of rectifying thyristors. The waveform of the output direct current of the convertor is detected and is supplied to a band-pass filter which selectively passes the harmonic component which has a frequency corresponding to that of the AC voltage source for the convertor. The existence of the component of this frequency is characteristic of an occurrence of a failure within convertor. The amplitude of the component passing through the filter is then detected by a zener diode, and a failure signal is generated when the amplitude exceeds a predetermined level.

Abstract: In a thyristor valve having a plurality of series-connected thyristors, each thyristor has an individual recovery protection device arranged in its entirety at the potential of the thyristor. For each thyristor, the protection device comprises a voltage-sensing member whch indicates the point of time when the thyristor takes up reverse blocking voltage. A time-determining member defines a certain time interval, counting from said point of time. Control members are arranged to deliver a control pulse for firing the thyristor if the off-state voltage of the thyristor during the time interval exceeds a predetermined value.

Abstract: When a-c power line voltage is rectified by a phase-controlled SCR rectifier bridge to develop an adjustable d-c bus voltage which is then converted by an inverter back to a-c for driving a load, such as a motor, line voltage disturbances, resulting from momentary power outages or major power reductions, will have a deleterious effect on the operation of the inverter system. Such disturbances will cause improper firing of the SCR's and the d-c bus voltage may increase considerably, disrupting the normal operation of the inverter system and possibly destroying the switching devices in the inverter. Immunization against the effects of the line voltage disturbances is obtained by shutting down or disabling the phase-controlled SCR rectifier bridge anytime such a disturbance occurs.

Abstract: The bridge converter comprises a number of switching elements and an electronic logic system which regulated the electric power levels by controlling the firing, i.e., the initiation of the conduction period of the switching elements.Cyclic firing of said elements allows the direct current to bypass the alternating current system with high power factor and negligible losses.

Abstract: A high voltage power converter has a number of thyristors interconnected. Symmetrical voltage dividers maintain equal voltage distribution across the thyristors. Each thyristor has a plurality of inductors associated therewith for reducing rapid current increases through the thyristors during firing which might injure the components and generate radio frequency interference.

Abstract: A regulated DC power supply has a converter having a plurality of switches which, upon proper regulation of their conduction, rectify an AC current. The converter produces a current feedback signal. A reference generator produces a plurality of adjustable reference signals each representative of one value of a load current and produces a predetermined, standby, reference signal representative of a standby load current. One of the adjustable reference signals, the standby reference signal, and the current feedback signal are added to produce a control signal. The control signal is compared to a signal representative of the AC source voltage. Firing signals, used to regulate the conduction of the switches, are produced in response to the existence of a predetermined relationship therebetween. In the event that all of the adjustable reference signals have a value of zero for a predetermined period of time, the firing signals will be inhibited from regulating the conduction of the switches.

Abstract: In a gate control circuit for a thyristor converter, in which thyristor valves each having a plurality of series thyristors are connected to form a bridge, a detector for detecting a forward voltage applied across one of the thyristors and a circuit for supplying a gate signal to the gate of that thyristor valve are provided. The gate control circuit further comprises a circuit for supplying, when a bypass pair operation of the thyristor converter is switched over to a deblock operation, a signal to the gate of a continually conductive thyristor valve according to a control signal to a thyristor valve to be operated in deblock with the continually conductive thyristor valve and also a gate signal to the continually conductive thyristor valve.

Abstract: A gate controlling circuit for a thyristor converter having an inverse bias voltage detecting circuit which detects the inverse bias voltage across a thyristor and is connected between the anode and cathode of serially connected thyristors in a thyristor valve. A gate signal to all of the thyristors is supplied when the output of the inverse bias voltage detecting circuit drops or becomes zero after all of the thyristors are turned off.

Abstract: In an electric power converting apparatus comprising a plurality of branches each including a plurality of serially connected semiconductor switching elements, a non-linear resistor is connected in parallel with each semiconductor switching element, and a voltage division element including serially connected capacitor and a resistor is connected in parallel with each semiconductor switching element. A reactor is connected in series with each one of the branches and an arrestor is connected in parallel with a serially connected reactor and an associated branch.

Abstract: A snubber circuit is connected between the anode and cathode of a gate turn-off (GTO) thyristor. To the GTO thyristor a saturable reactor is connected in series. A gate off signal is supplied to the gate of the GTO thyristor and to the saturable reactor as backward current to reset the saturable reactor.

Abstract: A monitoring device for semiconductor rectifiers which are located in a three-phase current bridge circuit, in which the bridge circuit is provided with two semiconductor rectifiers per rectifier branch, including a current-sensitive detector circuit connected to each pair of semiconductor rectifiers of each branch through a resistor, wherein when the semiconductor rectifiers are intact, the sum of all current flowing through the resistors is zero, as detected by the current-sensitive detector circuit.

Abstract: A power converter having improved efficiency and useful, for example, in the propulsion system of an electric vehicle. The power converter includes a dual chopper having an output level variable over a rather wide range for controlling the speed of the vehicle from stop to cruising. A commutating inverter is transformer coupled to the chopper for commutating thyristors in the chopper. Efficiency is considerably enhanced by programming the amount of energy in the commutating inverter in accordance with the power being delivered by the chopper so as to minimize power losses and thereby increase the range of the vehicle.

Abstract: A thyristor overvoltage protection circuit wherein an avalanche diode conducts to divert overvoltage energy from a thyristor to avoid self-ignition of the thyristor when the overvoltage reaches a particular level. A simulator circuit monitors the thermal loading on the conducting diode and activates an ignition pulse device if the thermal loading exceeds the safe operational range of the diode. The activated ignition pulse device ignites the thyristor so that the thyristor may divert the overvoltage energy and thereby discharge the diode.

Abstract: A frequency converter having a silicon controlled rectifier comprises a protection circuit which includes a series resonant circuit connected in parallel with the silicon controlled rectifier to generate a reverse voltage thereacross in response to a short circuit established in response to a commutation failure of the silicon controlled rectifier. An inhibit circuit is provided to respond to the reverse voltage by inhibiting the current flow through the silicon controlled rectifier to allow the same to restore to its locking state.

Abstract: A circuit arrangement for monitoring the current inbalance in two parallel-connected converter branches, each of which includes at least two series-connected converter valves. The anodes and cathodes, respectively, of adjacent converter valves in a given branch are connected together via cross-connections containing current transformers. A differential current transformer is provided at the output junction point of the two converter branches. Starting with the output signal of the differential current transformer, the exact current misdistribution for each adjacent converter valve pair is determined via summing amplifiers by adding the currents of the transverse transformers. A protective measure is triggered if a current misdistribution occurs.

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: 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: The disclosure is concerned with enabling modular power converter systems, including RF generators or transmitters involving such conversion, employing switching components such as SCRs in the power conversion, to fail in a soft manner as a result of transient electrical or other disturbances so as to permit continued system operation, through the use of individual module d.c. power supplies and circuit design that insures inverter module high output impedance even under SCR failure conditions and that mitigates against SCR failures caused by changes in load phase angle.

Abstract: A new and improved control subassembly for HVDC power converters and method of its use during transient faults affecting the A. C. system employed in the HVDC power transmission system to assure the presence of adequate firing and commutating voltages across the respective HVDC thyristor valves during selected intervals of the alternating current periods of the respective phases. The HVDC power converters used in the system include gating circuits for gating-on respective ones of the thyristor valves during selected intervals of the alternating current periods of the respective phases. The gating circuits include equidistant-spaced gate firing pulse generating circuits for supplying equidistant-spaced gating-on firing pulses to the gate drives for the respective HVDC thyristor valves of the HVDC bridge power converter during normal operation of the converter in the presence of symetrically-shaped A. C. system voltage waveforms.

Abstract: A commutation sensor circuit for a DC-to-DC silicon controlled rectifier (SCR) chopper circuit to protect against commutation failure by determining the commutation capability of the chopper. This determination is made by testing two conditions, first, the applied voltage is measured and used to predict the commutation voltage available after a main SCR has been gated on and a commutating capacitor charged, and second, the available commutation voltage is measured after the main SCR has been gated on and the commutating capacitor charged. The first test allows the chopper to turn on if the predicted voltage when compared to the current flowing is sufficient to commutate the chopper. The second test initiates a commutation if the current flowing in the chopper reaches the maximum commutating ability of the chopper.

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 sealed DC power converting station is provided with a bus bar group disposed at the central portion of the station and first and second groups of sealed controlled semiconductor switching units disposed on the opposite sides of the bus bar group. The switching units are respectively connected to the bus bar group through disconnectable gas insulated connection ducts. The station further includes a sealed smoothing reactor connected in series with a DC transmission line and arrestors provided for respective gas insulated connection ducts.

Abstract: A thyristor fault-detecting apparatus comprises a thyristor bridge with A.C. terminals connected to a three-phase A.C. power supply and having six thyristor arms, and an inductive load connected to D.C. terminals of the bridge. Each of the A.C. paths has a saturable reactor with an output winding so set as to be excited by the line current within the range from .pi./3 to 2.pi./3 (rad). Output voltages of the reactors are rectified and added, so that a fault in the thyristor is detected by the disappearance of the added output.

Abstract: A circuit comprising first and second rectifiers for supplying rectified current or voltage to a storage capacitor located at the output of the circuit. The circuit includes a control circuit operatively coupled between the output and the silicon controlled rectifiers to insure that alternate ones of the silicon controlled rectifiers will supply the rectified current or voltage to the storage capacitor as needed.

Abstract: A protection circuit for protecting the thyristors of a series circuit of several thyristors, each of which has a corresponding firing circuit to which its anode-cathode voltage is applied.

Abstract: A high-voltage thyristor converter having a plurality of series-connected thyristor units and a gate control system. Each of the series-connected thyristor units has a plurality of series-connected thyristors and a gate-drive power supply circuit (hereinafter referred to as a gate power supply) connected between both extreme ends of the series-connected thyristors for supplying gate-drive power to the thyristors. The gate control system detects whether or not an output voltage of the gate power supply of at least one of the series-connected thyristor units is at least equal to or higher than a predetermined value and transmits a gate signal simultaneously to all of the thyristors when the output voltage is higher than the predetermined value, so that a protective action for preventing breakdown of the thyristors can be performed upon an instantaneous power failure or the like trouble.

Abstract: An overvoltage responsive triggering circuit for a main high power thyristor comprises a plurality of n auxiliary thyristors and electric energy storing means connected in series across said main thyristor. The auxiliary thyristors are poled to conduct forward current in the same direction as said main thyristor and have an aggregate forward breakdown voltage greater than a predetermined threshold magnitude. Said threshold magnitude is greater than the aggregate forward voltage of said n auxiliary thyristors minus the forward breakdown voltage of one of said auxiliary thyristors. Between the anode and another electrode of said one auxiliary thyristor there is connected secondary voltage breakdown means having a blocking voltage less than the forward breakdown voltage of said one auxiliary thyristor, whereby said triggering circuit becomes conductive in the breakdown mode at said threshold voltage magnitude.

Abstract: In a high current power supply controlled by thyristors mounted in antiparallel in the primary of the power transformers, saturation of the transformers is prevented by a detection circuit responsive to an unbalance in such bilateral switch and protective action is automatically triggered. Display is provided to identify the defective bilateral switch.

Abstract: A circuit for monitoring conduction of a phase controlled, alternating current switch, e.g., a thyristor switch, looks at the voltage across the switch. This voltage has a high dv/dt whenever the switch stops and starts conducting current. The voltage detected from across the switch is processed as follows: it is differentiated to produce a train of voltage spikes of very short time duration and some lesser voltages; the lesser voltages are removed; the spikes are then amplified and extended in time duration; and finally the time extended spikes are integrated. The integrated voltage is a train of alternate positive and negative voltages averaging zero during normal switch operation. However, when the switch conducts one of the half cycles only, the integrated voltage rises in one polarity sense depending upon the half cycle conducted. A control circuit becomes operative upon the integrated voltage attaining a predetermined value to initiate a control function such as de-energize the switch.

Abstract: A rectifier for a medium voltage rectifier system as well as for high voltage-direct current transmission includes a plurality of thyristor switches. The switches have asymmetric voltage breakdown strengths, the asymmetry being at least 10% for the forward blocking direction compared with the reverse blocking direction. The thyristor switches are dimensioned voltage-wise to safely block even long lasting overvoltages in both the forward and reverse blocking directions occurring during operation and to withstand momentary surge and switching voltages limited by an overvoltage suppressor in the reverse blocking direction.

Abstract: An over-voltage interrupt circuit is provided which senses the local output of the phase controlled regulator. A reference is generated which is utilized in a comparator as the over-voltage threshold. When the sensed regulator output is above this threshold setting an override signal is produced which overrides the condition of the on/off control. The comparator is arranged to have a lower reset threshold value than the setting threshold so that the on/off control is again switched in response to the sensed voltage dropping below the reset threshold level. If the over-voltage condition persists, the comparator continues to set and reset and, accordingly, the on/off control is continually switched off and on giving a limited average voltage output from the regulator. The on/off control operates through a walk-in circuit which controls the voltge during turn on and off to prevent over and undershoot voltage problems.

Abstract: Circuitry for providing high voltage DC power from commercially available 60 hertz AC utility power. The incoming 60 hertz AC voltage is rectified to a DC voltage. This DC voltage is then converted to a high frequency AC voltage by means of a sine wave inverter. This high frequency sine wave voltage is then converted to a different voltage and rectified by a voltage doubler. The inversion and rectification are under the control of logic circuitry which includes means for sensing line faults to provide circuit protection.

Abstract: A short circuit detector is provided for a compact power supply system in which a plurality of power supplies may be operated in parallel. The detector senses when a voltage drop in a bus indicates a possible short and then energizes solid state devices to turn the system off for a prescribed period of time. After the prescribed period of time has passed, the system will attempt to restart. If the ground has been cleared, system operation will be restored. If not, the system will again be shut down for the prescribed period.