Abstract: A polyphase variable frequency inverter with output voltage control provides a polyphase AC output from a constant potential DC supply, and comprises a chopper circuit and an inverter circuit. The chopper circuit further comprises a silicon controlled rectifier in parallel with a reverse biased diode. The anode of the silicon controlled rectifier and the cathode of the reverse biased diode are connected to the positive terminal of the constant potential DC supply while the cathode of the silicon controlled rectifier and the anode of the reverse biased diode are connected to the respective silicon controlled rectifiers and reverse biased diodes of the inverter circuit. The inverter circuit further comprises a plurality of branches, each including a first silicon controlled rectifier in series with a second silicon controlled rectifier, each such silicon controlled rectifier having in parallel therewith a reverse biased diode.

Abstract: One diode each is connected in antiparallel fashion to each load thyristor, said diode being a component of a commutation installation for the corresponding load thyristor. The commutation installation manifests an LC-series oscillatory circuit dimensioned for the specified load current and, for each load thyristor, a controllable commutation thyristor connected to a control circuit. Each commutation thyristor forms a closed circuit with the LC-series oscillatory circuit and its diode. One saturable choke each is connected in series with each thyristor and each diode. One RC-element each is connected in parallel with each thyristor and each diode, and saturation means are present for the chokes associated with the load thyristors. The inverter load may be the high voltage transformer of an x-ray generator.

Abstract: An induction heating apparatus includes a pair of thyristors inversely parallel connected to receive power from a low frequency energy source, a commutating circuit and a gating control circuit for supplying control pulses to the thyristors to produce a forward halfwave current through the commutating circuit which in return produces a backward commutating current to the thyristors. The gating control circuit includes a pulse transformer having a pair of secondary windings connected to the thyristors and a primary winding responsive to control pulses supplied from a pulse generator to produce a positive gating pulse in each of the secondary windings to drive one of the thyristors into conduction depending on the polarity of the source voltage to produce the forward current.

Abstract: In the operation of a control arrangement for the direct voltage of an inverter station which inverter station includes a plurality of thyristor bridges which are connected in series at their direct voltage side and connected to a three-phase mains via a plurality of variable ratio transformers each individually associated with a respective thyristor bridge, a plurality of extinction angle circuits each associated with a respective thyristor bridge, and a total control circuit for controlling the voltage of all thyristor bridges together, the control circuit providing an output corresponding to the direct voltage of the inverter station and responding to a setting value representative of the transformer stage adjustment which operates in synchronism for all thyristor bridges, the control arrangement is matched to the control path by comparing a measured value which corresponds to the direct bridge voltage of each thyristor bridge with the instantaneous maximum value of the measured values for all thyristor br

Abstract: In an inverter apparatus of the type comprising a plurality of thyristors connected between a DC source and an AC load, a control circuit for sequentially turning ON and OFF the thyristors according to a predetermined sequence, and a reverse bias circuit including a pair of power transistors respectively connected in series with the DC source and ON.sup.. OFF controlled by the control circuit for applying a reverse bias to the thyristors to effect simultaneous commutation thereof, and a pair of diodes connected across the DC source, there are provided a second thyristor connected between the plurality of thyristors and the power transistors and turned ON at the time of commutation of the plurality of thyristors by the control circuit and a reactor connected in parallel with the second thyristor.

Abstract: An illumination control system for gas discharge lamps which can be dimmed is provided in which a central inverter produces a sinusoidal output voltage at about 23 kHz. The amplitude of the inverter output is adjustable to dim the lamps. A transmission line consisting of spaced wires having respective thick insulation sheaths distributes the high frequency power to remotely located assemblies of ballasts and lamps. The ballasts consist of passive linear components. A high power factor rectifier network is disclosed for providing a d-c input to the inverter from the 50/60 Hz mains. The inverter circuit is provided with novel controls for gradual start-up and turn-off and is protected against load fault currents and internal fault currents. Automatic and manual resets are provided for internal fault current and load fault current, respectively. The basic inverter circuit consists of two alternately conducting controllably conductive power switching devices.

Abstract: An induction heating apparatus of the invention is provided with a pair of inversely parallel connected thyristors which receives power from a low frequency energy source. Depending on the polarity of the source voltage, one of the thyristors is triggered into conduction by a control pulse generated in delayed response to a sensed forward bias potential at its anode for the purpose of supplying a forward current to a commutating circuit which is tuned to a high frequency in the ultrasonic range, whereupon a backward current is generated. The backward current is commutated through the other thyristor to complete a high frequency oscillation. A detector is provided to detect when the magnitude of the backward commutating current reaches a predetermined value for the purpose of terminating the trigger control pulse.

Abstract: A method for control of a static valve converter consists of determining the difference between the actual and desired control pulse phases by the use of an equidistant pulse sequence, the frequency of which being equal to the coversion frequency, the pulse sequence phase being selected so that the mean difference between the equidistant pulse phase and the phase of the respective control pulses of all valves is equal to zero, and the pulse phase difference being determined for each individual valve. A control pulse automatic balancing unit incorporated in an apparatus for realizing the method of the present invention comprises an equidistant pulse sequence assembly, a shaping element, correcting signal circuits and logical AND elements equal in number to the number of conversion phases, and also logical circuits equal in number to the number of coversion phases. Each logical circuit comprises two logical AND elements, and a logical OR element connected to the outputs of the AND elements.

Abstract: A voltage regulating device for a power generating system with inverter circuits including two sets of switching elements each of which is alternately on-off controlled, having delay circuits for controlling delay time in accordance with the load voltage, and characterized in that supply voltage to the load is maintained at a constant level by forcibly turning off either set of the switching elements during the period when the said set of the switching elements are to be turned on.

Abstract: The proposed digital control device controls a d.c. thyristor-pulse converter and comprises a decoder connected to a clock pulse counter and a reversible counter. The device further includes a control unit, a matching unit containing four AND gates and a sign flip-flop, and a switching unit having six AND gates and two flip-flops. A first AND gate of the switching unit is connected to a control electrode of a first thyristor, a second AND gate of the switching unit is connected to a control electrode of a second thyristor, a third AND gate is connected to a control electrode of a third thyristor, a fourth AND gate is connected to control electrode of a fourth thyristor, a fifth AND gate is connected to the control electrodes of the first and third thyristors, and a sixth AND gate is connected to the control electrodes of the second and fourth thyristors. The clock pulse counter and the AND gates are connected to the flip-flops of the switching unit.

Abstract: An auxiliary commutation circuit to compensate for transient type overload conditions of an inverter comprises a pair of oppositely charged capacitors controlled by separate switches, each operable at a particular time during the conduction cycle of the main thyristors to provide additional stored energy for commutation during overcurrent conditions. A current detector senses the load current and provides a signal to an auxiliary gate whenever the rate of change in the load current or its absolute magnitude exceeds a preselected value. In response to the overcurrent signal and a timing signal, the auxiliary gate renders the appropriate switch operative coupling the charged auxiliary capacitor in parallel with the primary commutation capacitor so that the combined electrical energy stored on both capacitors is available for commutation. After the commutation period the auxiliary gate maintains the switch in its open state for a sufficient period of time to allow the auxiliary capacitor to be recharged.

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: 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 power supply arrangement that substantially eliminates the effects of the sidebands and harmonics at the switching frequency of the power supply on the RF carrier of an amplifier or other unit being supplied power. The switching frequency of the power supply arrangement is continuously varied in frequency at an appropriate rate and deviation with the result that a band of frequencies replaces the fundamental switching frequency of the power supply and all harmonics so that noise created by the switching frequency signal and the RF signal are then similarly diffused. The net power present as spurious noise in the amplifier unit is constant with the maximum amplitude of the noise as viewed, for example, in a doppler filter being substantially reduced. In a radar transmitter, for example, the transmitted pulse frequency appears as PRF sidebands of the CW frequency and the extraneous modulation from the switched power supply provides sidebands of the PRF sidebands.

Abstract: A current source inverter having a converter for changing alternating current into direct current, an inverter for changing the d.c. output of the converter into alternating current, and a reactor interposed between the converter and the inverter comprises power failure detecting means for detecting the power failure of the a.c. input of the converter. The power failure detecting means is constructed of square wave generator circuits which generate square waves when voltages in respective polarities of respective phases of the a.c. input exist, an adder which adds the outputs of said square wave generator circuits, and a comparator which compares an output of said adder with a predetermined value and which provides an output when the adder output is below the predetermined value.

Abstract: The invention comes within the field thyristor bridge control.A device for controlling a Graetz rectifier bridge for driving a synchronous machine which operates at variable speed, it being connected to this machine by its AC terminals and its voltage at the terminals being substantially proportional to its frequency, characterized in that the firing pulses of each thyristor of the Graetz rectifier bridge come from the comparison of a control signal U.sub.c chosen as a function of the required firing angle .alpha. of the thyristor to be fired, with a sinusoidal phase reference curve whose amplitude is made independent from the operation frequency of the Graetz rectifier bridge.The invention applies in particular to the driving of synchronous rotating machines which operate at variable speed.

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: A control device for a pulse-width modulated inverter comprises means for generating as a carrier wave a triangular wave synchronizing with an AC output from the inverter, means for generating as a modulating wave a train of rectangular wave pulses which synchronize with the triangular wave and have a width corresponding to a section effective for a modulating operation and a predetermined amplitude, voltage level setting means for setting the amplitude of the train of rectangular wave pulses, and means for modulating the triangular wave with the train of rectangular wave pulses and generating a control pulse for the AC output.

Abstract: The disclosed supply utilizes the capability of two-way power flow, from a DC source to the load and from the load to a DC source, so as to be able to track a desired output wave form while running reactive loads. This method of operation requires minimum filtering for loads of various power factors and transient characteristics. Two equal and opposite DC sources, such as batteries, furnish and accept current, through switches, to and from an inductor-capacitor filter to which the load is connected. A feed-back circuit compares the voltage furnished to the load with a reference of the desired output wave shape, so as to control the switches in such manner as to force the output voltage to follow that wave form.

Abstract: A firing pulse generator for sequential firing of thyristors digitally synthesizes time dependent references associated in succession with the respective thyristors with a hard pulse, and predetermined critical counts on a time dependent reference are identified representing the first and second end-stops defining the permissible fire-angle range. A substitute for the hard pulse is generated when the hard pulse is advanced, and when it is retarded in relation to predetermined limits, e.g. the end-stops. The time dependent reference is generated over a range sufficient to cover the permissible fire-angle range defined by the end-stops. Blocking of an illegal hard pulse is effected independently from the generation of a hard pulse. Pulse suppression is performed independently from the generation of a hard pulse, or of a substitute pulse.

Abstract: A control system is provided for the accurately timed control of switching inverter circuitry; for example, an inverter that produces a 115VAC/60HZ output from a 12 V DC source such as a vehicle battery. The control system utilizes an internal reference source and supervisory control circuitry to determine accurate and orderly start up, shut down, control of the inverter switching elements and automatic shut down upon the occurrence of predetermined sensed conditions including low input voltage from the source and excessive output current through the load. The switching elements of the inverter are each controlled to produce respective outputs of predetermined active/inactive duty cycles each switching cycle with an accurate inactive period being established between the active periods of each switching element.

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: An inverter circuit comprises a reactor and a capacitor connected in series to a load to supply the load with a series resonance high-frequency power, a secondary winding provided at the reactor, and means for feeding a voltage generated in the secondary winding back to a power supply through switching means of a thyristor. The switching means is made conductive to feed the voltage generated in the secondary winding back to the power supply when supply voltage detecting means detects that a supply voltage exceeds a predetermined voltage.

Abstract: Upon a stop command, the current conducting state of the main valves and the recovery valves of an inverter with bridged valves is monitored. A change of the firing pulses for the main valves is blocked if the valves connected to one d-c bus of the inverter conduct current simultaneously. After a predetermined time has passed or upon the arrival of a monitoring signal that the current in the inverter is extinguished, the transmission of the firing pulses to the controlled main valves of the inverter is then blocked.

Abstract: A metal based cookware induction heating apparatus having an improved power supply and control circuit comprised of a chopper inverter including a gate controlled power thyristor coupled to and supplying an induction heating coil with periodic energization currents. A full wave rectifier supplies rectified, unfiltered, unidirectional high voltage excitation potential to the chopper inverter which converts the excitation potential to a comparatively high frequency of the order of 20 kilohertz for supply to the induction heating coil. A gating circuit is provided for driving the chopper inverter directly from the rectified high voltage excitation potential supplied by the rectifier.

Abstract: A power control or conversion apparatus comprises a combination of a controlled electric valve bridge and an electric valve bridge being coupled to each other in anti-parallel combination; DC reactors inserted in series in positive and negative electric paths coupling the controlled electric valve bridge with the electric valve bridge in anti-parallel combination; extension means for reverse-biasing the controlled electric valves of the controlled electric valve bridge to extinguish them; and switching means inserted in the coupling portion between the respective electric valve bridges and a DC power source. The extinction means and the DC reactors cooperate to forcibly commutate the controlled electric valve. The DC reactors also make current smooth.

Abstract: A DC to DC converter employs resonant switching to turn switching power devices on and off at zero current. Two series resonant circuits are formed by two inductors connected in series between a voltage source and a power switch and a capacitor connected between the junction of the two inductors and a source of reference potential. The values of the two inductors are chosen so that the natural resonant frequency of the second inductor and the capacitor is high compared to the natural resonant frequency of the first inductor and the capacitor. The power switch may be a semiconductor switch, such as a silicon controlled rectifier or a junction transistor. Both non-isolated and isolated outputs may be provided in buck or boost conversion. The converter can be used as a voltage regulator by the addition of output sensing, comparison with a reference voltage, and suitable on-off control.

Abstract: A naturally-commutated, voltage-fed direct-current (DC) to alternating-current (AC) power converter employing thyristor elements couples a DC power system with an AC power system without the requirement to force commutation. To effect natural commutation, the fundamental component of current flowing between the DC system and the AC system must lead the DC system switching voltage.

Abstract: A power circuit arrangement for a power conditioning system adapted to supply variable frequency, variable magnitude voltage to an electromagnetic device such as an electric motor having a center-tapped winding includes first and second inverting thyristors connected to the respective winding ends and connected in series with a transistor chopper across a unidirectional source so that the inverting thyristors may be gated on alternately at a relatively low modulation frequency while the chopper is time ratio controlled at a higher carrier frequency to selectively vary the voltage applied to the winding; a capacitor in shunt to the chopper which is overcharged due to winding leakage reactance when the chopper is turned off to reverse bias and "soft" commutate the thyristors when they are not conducting load current; a free-wheeling thyristor connected between the winding center tap and the chopper and poled to form a low-impedance free-wheeling path for winding current in series with the inverting thyristors w

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: A power supply circuit for a high voltage driven device, particularly a magnetron, is described. The power supply circuit comprises first and second switching elements, an inverter circuit including a commutating reactor connected in series with the first and second switching elements and a capacitor connected to a center tap of the commutating reactor, a transformer connected to an output of the inverter circuit, and a third switching element connected in parallel with a series circuit comprising the capacitor, the primary winding of the transformer and a portion of the commutating reactor. When the magnitude of a current flowing in the transformer exceeds a predetermined level, the third switching element is fired to establish a discharge loop for the capacitor through the series circuit whereby the amplitude of the current supplied to the transformer is limited below the predetermined level.

Abstract: A circuit arrangement is disclosed for supplying an electric machine from a d-c voltage source. The circuit arrangement comprises a self-commutating inverter having valve branches that can be fired and extinguished and d-c voltage inputs to which electronic switching members are connected. In accordance with the invention, a capacitor is connected to the output of the inverter via a rectifier, and the d-c voltage outputs of the latter are connected via current paths with the poles of the d-c voltage source. To obtain at least partial recovery of the energy stored in the capacitor ohmic resistors are arranged in the current paths. Complete energy recovery is, in turn, realized by arranging controlled electronic valves in the current paths.

Abstract: A variable speed static controlled induction motor is voltage regulated under variable frequency by controlling the inverters under constant pulse width while maintaining a constant volt-hertz ratio through the feedback voltage control loop.

Abstract: A circuit suitable for use in an induction range. The circuit includes a resonant inverter having first and second gate controlled thyristor switches, the main conduction paths of which are serially connected between the power supply terminals. Trigger pulses for the switches are derived from the current supplied to the inverter load coil. The pulses are timed to prevent the first switch from being closed before the second switch has opened so that both switches can never be conductive at the same time. It also includes circuitry for stopping inverter operation in the event of an overcurrent condition and circuitry for adjusting the inverter output power.

Abstract: A circuit for detecting a missed commutation in an inverter. The circuit includes means coupled to the center tap of a commutating interval current limiting reactor which is connected in series with and interposed between a pair of gate controlled rectifiers for generating a first signal upon detecting and for the duration of an interval when both of the rectifiers are ON. The circuit further provides means, responsive to a first pulse used to initiate an interval when either of the pair of rectifiers is to be "ON", for generating a second signal. Also provided is a means responsive to the first and second signals for generating a control signal to cause cessation of the operation of the inverter, if the first signal is absent during the total occurrence of the second signal.

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.