Abstract: A converter circuit arrangement is specified having a rectifier, an intermediate circuit and an invertor connected thereto. In order to protect the circuit against failures and overvoltage, a protection circuit which comprises, in particular, varistors is connected between the two partial rectifiers of the rectifier.

Abstract: A three-phase controlled rectifier bridge for converting alternating current to direct current includes six segments for each of the positive and negative polarities of each of three AC phases. Each of the segments has a semiconductor controlled rectifier element responsive to a control signal to control current conduction within the segment. A conduction monitor, which is provided for each of the AC phases, monitors a corresponding one of the AC phases to provide a conduction monitor signal. A first shunt current sensor senses current of the segments for the positive polarity of the AC phases and provides a first current signal. A second shunt current sensor senses current of the segments for the negative polarity of the AC phases and provides a second current signal.

Abstract: A power converter comprises a pulse generator capable of outputting two different levels of gate power. A thyristor (LTT) is turned on by the first gate power output from the pulse generator, and the second gate power is supplied to the thyristor (LTT) during the transient period from the time the thyristor valve current is cut off to the time the withstand voltage of the thyristor (LTT) recovers to the rated value. The second gate power is set at a low level by which the thyristor (LTT) will not be turned on when the second gate power with the normal level of voltage is applied to the thyristor.

Abstract: A two-wire power supply switch connected in series with a load between two poles of an alternating current mains electrical power supply conventionally includes a main triac between two terminals of the switch which is turned on by the conduction of an optotriac with a time-delay relative to the zero crossing of the voltage between the switch terminals determined by the breakdown voltage of a series of Zener diodes. The switch includes a power supply unit with a rectifier bridge connected to one terminal directly and connected to the other terminal via a capacitor. An auxiliary triac shunting the capacitor is turned on by the optotriac on each zero crossing of the voltage between the switch terminals. This optimizes conditions when the switch is open and when the switch is closed separately.

Abstract: An electrostatic precipitator circuit has an input terminal supplied DC voltage, an output terminal connected to a precipitating capacitor, a storage capacitor connected between ground potential and the input terminal, and a recovery capacitor whose one electrode is applied with ground potential. The circuit further includes a current path switching unit having a common terminal and first and second switch terminals to be connected to the common terminal, the common terminal being connected to a non-ground electrode of the storage capacitor.

Abstract: A control circuit for an H-bridge circuit comprises a single capacitor, a charge/discharge circuit for charging/discharging the capacitor in response to a control command signal, a voltage detector circuit for detecting a voltage appearing across the capacitor and a hold circuit for holding the control command signal in response to of a predetermined voltage detected by the voltage detection circuit. Charge and discharge of the capacitor is controlled in dependence on changes in the control command signal to thereby prevent occurrence of a through-current flow in the H-bridge circuit while allowing the bridge circuit to be changed over to the operation state indicated by the control command signal after lapse of charge/discharge period. The control circuit for the H-bridge circuit can be implemented in a miniaturized size with high reliability of operation while decreasing the number of elements attached externally even in the case where the control circuit is implemented in the form of an integrated circuit.

Abstract: A rectifying saturable reactor generates a magnetic force in a magnetic iron core in response to a current that flows through an electronic circuit. The saturable reactor makes use of saturable magnetic flux in view of a hysteresis loop of a magnetic material for rectification and selects the saturated magnetic flux to be greater than an integrated value of a voltage applied to the rectifier in the rectifying circuit. In order to improve a rectifying performance, a no cut and one turn structure or an equivalent is introduced into a magnetic core for providing a hysteresis loop that varies as much as possible in magnetic induction.

Abstract: A control system for energizing a direct current (DC) motor with alternating current (AC) power includes a first voltage sensor for a peak voltage of AC power; a second voltage sensor for a counter electromotive force (EMF) of the motor; a current sensor for an armature current of the motor; a digital processor having a first current controller responding to sensed armature current and a current reference, a cooperating second current controller responding to sensed peak voltage, sensed counter EMF and the current reference signal, and a gating circuit responding to the controllers; and a thyristor converter circuit sequentially gating portions of half cycles of AC power to the motor in response to firing signals from the gating circuit. The controllers may control a gate angle of the firing signals, the control system may include a third voltage sensor for a terminal voltage of the motor, and the armature current may have discontinuous and continuous waveforms.

Abstract: A semi-conductor bridge thyrister converter circuit for converting AC power into DC power with suppression of the higher harmonics generated by the circuit including a semi-conductor converter circuit, a control circuit, and instrument transformers for measuring the voltages and the currents at the source and the load side at a node. On the basis of the outputs of these transformers, the control circuit controls the control delay angle and the overlap angle of the thyristers of the semi-conductor converter circuit such that higher harmonics generated by the converter current are reduced to a minimum as seen from the power system side.

Abstract: A differential charging circuit comprising an active switch device controlled by a differential trigger circuit and a current impedance device to charge a storage battery through an intermediate storage capacitor. A capacitor and commutating inductance are also connected in series with the output to reduce ripple. The differential active switch device is controlled based on a reference potential developed across the current impedance device, and this enables frequency-controlled charging of the storage battery through the commutating type inductance.

Abstract: A control system for one or more dc motors in which thyristor power modules selectively gate portions of half cycles of ac voltage to the motor field and armature windings, has digitally implemented parallel inner control loops for the armature which each generate an intermediate control signal to which proportional plus derivative control action has been applied. Logic selects the intermediate control signal which phases back firing pulses for the thyristor power modules the most for application to a common digital integrator which produces a control signal having proportional plus integral control action. The voltage across each of the thyristors is monitored and used to detect continuous and discontinuous current operation for adjusting integrator gain.

Abstract: To minimize injury during electrofishing while inducing a high degree of electrotaxis, a packet of DC pulses having sharp leading edges and preferably an exponential or square decay are transmitted under water between an anode electrode and a cathode electrode several times each second to stimulate contraction of the red muscle tissues and bring about electrotaxis without inducing epileptic seizure of the white muscle tissues of fish and thereby avoiding injury to the fish.

Abstract: A method and apparatus for protecting thyristors in a power converter from overvoltages. Voltage detectors determine if the forward voltage of each thyristor has increased in the converter. If such an overvoltage occurs during a predetermined period after the conduction of the thyristor, forced triggering of all the thyristors prevent damage to the thyristors.

Abstract: To minimize injury during electrofishing while inducing a high degree of electrotaxis, a packet of DC pulses having sharp leading edges and preferably an exponential or square decay are transmitted under water between an anode electrode and a cathode electrode several times each second to stimulate contraction of the red muscle tissues and bring about electrotaxis without inducing epileptic seizure of the white muscle tissues of fish and thereby avoiding injury to the fish.

Abstract: The invention relates to an AC voltage supplied rectifier circuit with a downstream smoothing capacitor. A prior art problem with this type of circuit was that the inductive impedance of the supply voltage caused a practically umdamped oscillation between the inductive supply impedance and the smoothing capacitor during start-up which caused the voltage to rise to about twice the stationary value. A rectifier circuit is provided which substantially prevents the over-oscillation having at least one controllable rectifier which brings the rectifier to a conductive state during the charging period of the smoothing capacitor over such a time that the output direct voltage of the rectifier circuit exceeds the momentary capacitor voltage by no more than a predetermined limited value.

Abstract: In a gate pulse generator for a thyristor converter of the type in which in order to fire thyristors of the thyristor converter in which each arm is comprised of a plurality of series-connected thyristors, the gate pulses are generated in response to the gate command signal and the thyristor forward voltage signal and are converted into the light signals which in turn are transmitted to the thyristor converter, whether or not the forward voltage signal exists when the gate command signal is generated is detected and when the forward voltage signal is generated prior to the generation of the gate command signal, the pulse duration is narrowed to a minimum required for firing the thyristor.

Abstract: The invention relates to a method and to an arrangement for controlling the respective conduction times of two directionally opposed electrical devices (9,10) which are mutually connected in parallel and permit current to pass therethrough solely in one direction, and which also permit current (I.sub.2) to pass through the primary winding (2) of a transformer during a respective half-period of an A.C. voltage (U.sub.1) applied to the primary winding, this control being effected so that the magnetizing current through the transformer can be advantageously minimized and/or held beneath a given limit value when an asymmetric load (4,5) is applied to the secondary side (3) of the transformer. A magnetizing current in the primary winding corresponding to the load (5) of the secondary winding (3) is controled through the agency of different conduction times of the two directionally opposed devices (9,10).

Abstract: A control system for controlling high power from an AC source for electrostatic precipitators. The AC power is gated both on and off during the same half-cycle of the AC sources. The gating off of the AC power occurs at a time substantially different from the time of the zero crossings of the AC source. The AC source may be gated on and off respectively before and after each peak to provide high voltage to the precipator electrodes while the period of such pulsing is kept short enough to prevent arcing. Additionally, the source may be gated on after one peak and gated off before the next peak, thereby providing high voltage to the electrodes without applying the peak voltage of the AC. Further in accordance with the invention, such gating may be performed using gate turn-off thyristors. The pulses may be symmetric about the peaks or about the zero-crossings of the source. The source may also be gated on and off a plurality of times during each half cycle.

Abstract: A high tension power supply for use in an x-ray tube drive circuit which uses a step-up transformer to raise an input line signal to the desired voltage level. A partially open bridge or other suitable means permits only half cycles, for example positive half cycles, of the transformer output to be applied to fire the x-ray tube. Saturation of the transformer core during unused half cycles, for example negative half cycles, is prevented by adding a compensating impedance in series with the circuit passing the unused half cycle to the transformer primary, the increased voltage drop across this impedance as current increases in response to the transformer approaching saturation reducing the voltage across the transformer so as to maintain the average voltage across the windings during both half cycles substantially equal. This achieves "constant phase" exposures without transformer saturation.

Abstract: A DC power supply which generates little or no harmonics on the supply line includes a bridge circuit having high frequency controlled unilateral switching devices in the four legs thereof and a high frequency filter capacitor connected across two opposed junction points of the bridge to which is also connected a source of input power. The other two opposed junction points of the bridge are connected to a DC loop circuit which in one embodiment maintains a constant current through a load device connected in the loop and in another embodiment maintains a constant voltage. In the constant current embodiment a storage inductor is provided and energy is transferred to and from the storage inductor in accordance with the high frequency switching of the unilateral switch devices. The on and off times of the switch devices are governed by a control circuit which measures the current in the DC loop and compares it with a desired value.

Abstract: The power supply installation for a direct current railroad comprises two diode bridge-connected circuits, only two thyristor breakers each connected in parallel to each of the two diode bridge-connected circuits, four dc disconnecting switches each connected between a diode bridge-connected circuit and one of four electric car power supply lines constituting a double track, separately. Further, the two diode bridge-connected circuits are connected by a dc disconnecting switch closed only in case of an accident. In case a ground fault occurs at a power supply line, a powering current to the defective line is interrupted by one of the breakers, together with an extension power supply current supplied from an adjacent substation, without exerting an influence of accident upon the other power supply lines. Further, even if one of the breakers is broken, powering currents are kept supplied to all the power supply lines through a mutual spare bus bar.

Abstract: A power converter having an ac side connected through a reactor to an ac power source and a dc side connected to a smoothing capacitor and a load, the converter being capable of converting and inverting electric power in accordance with the pulse width modulation control, characterized by comprising: a voltage detection circuit for detecting a voltage on the side of the ac power source when viewed from the reactor; a first judgement section for detecting that the amplitude of a voltage component on the ac side of the power converter, which is included in the ac power source voltage, is above a predetermined value on the basis of an output signal from the voltage detection circuit to produce a signal indicative of the judgement result; a second judgement section for detecting that the amplitude of the ac power source voltage is below the predetermined value to produce a signal indicative of the judgement result; and a gate circuit for performing logical sum of the outputs from the first and second judgement se

Abstract: The present invention provides an optically controlled power converting apparatus using light trigger/light quench electrostatic induction thyristors, as switching elements, which can execute the switching operations at a high speed being when they are supplied with light trigger pulses and light quench pulses. By supplying the light trigger pulses and light quench pulses at the timings corresponding to the pulse width modulation, the light trigger/light quench electrostatic induction thyristors can perform predetermined power converting operations.

Abstract: An electronic power supply that converts alternating current to a regulated DC voltage with high efficiency is accomplished by a switch that connects the input AC power source directly to the DC output filter capacitor. This occurs when the input voltage equals the output voltage, and the output voltage is less than the set value.This power supply can be used with low impedance AC power sources capable of providing high surge currents such as commercial utility lines.

Abstract: A novel high-voltage pulse power source comprising an ON-OFF type high-voltage switch element, as high-voltage switch element, which can be reset in OFF state immediately after an ON action, and a current blocking mechanism arranged in the charging power source, whereby an output current from the charging source is inhibited by said current blocking mechanism to stop charging and generating of any dynamic current flow into the load during period of time from an ON action of said ON-OFF type high-voltage switch element till an OFF action of the same, and the flow of said output current is restored during an OFF state of said ON-OFF type high-voltage switch element after an OFF action of the same. In addition, a novel pulse-charging type electric dust collecting apparatus equipped with said novel high-voltage pulse power source.

Abstract: A power supply system for supplying a load current to a load including a serially connected circuit of a controlled rectifier, a switch and a capacitor. A diode is connected in parallel with the capacitor or with a serially connected circuit of the switch and the capacitor and a control circuit. Which controls the controlled rectifier such that when a first voltage between the capacitor is larger than or equal to a specified voltage the controlled rectifier is operated as bypass pair mode and when the first voltage is below the specified voltage the controlled rectifier is operated as current control mode. A method for starting a power supply system is also disclosed.

Abstract: A rectifier circuit for receiving an A.C. electrical power signal at a pair of circuit input terminals and for providing a rectified, D.C. electrical power signal at a pair of circuit output terminals includes a primary transformer winding connected to receive the A.C. electrical power signal, a plurality of secondary transformer windings, and a semi-conductor rectifying and switching circuit which supplies a D.C. electrical power signal to a storage capacitor connected across the circuit output terminals. A control circuit sequentially actuates the semi-conductor switches such that differing combinations of the secondary transformer windings are sequentially connected across the storage capacitor during each successive half cycle of the A.C. electrical power signal. By this arrangement, the charging current supplied to the capacitor and the charging potential across the capacitor fluctuate minimally during most of each half cycle and the A.C.

Abstract: A circuit for converting an AC potential to a regulated DC potential which circuit consumes a minimum of power and is relatively inexpensive to build is described. A capacitor is used to couple the AC potential to a rectifier. The duration of current flow through the capacitor is controlled to obtain the regulation. An on or off switching device is used such as an SCR, eliminating the current flow regulation devices often used in regulative power supplies. The invented circuit is particularly useful for providing a regulated DC potential in a switching power supply.

Abstract: A phase detecting apparatus comprises a first PLL and a second PLL having a response time shorter than the response time of the first PLL. An AC voltage signal produced by the first PLL which is in phase with the detected AC voltage except until the expiration of the response time of the first PLL after an abrupt change in the phase of the detected AC voltage is normally applied to the second PLL. Until expiration of the response time of the first PLL after rising of the detected AC voltage to a certain level, the detected AC voltage is applied, in place of the AC voltage signal produced by the first PLL, to the second PLL. The second PLL provides a digital signal indicative of the phase of the detected AC voltage.

Abstract: A method for simultaneously triggering a plurality of serially connected SCR's transfers energy from a relatively low voltage energy source to each of a plurality of energy storage devices which are coupled respectively to the gate of a corresponding SCR through a respective switching device. The energy from each storage device is simultaneously discharged into the gate of each respective SCR by a respective trigger signal from the low voltage energy source to each respective switching device.Apparatus for simultaneously triggering a plurality of serially connected SCR's comprises a pulse transformer for transferring energy from a relatively low voltage source of energy.

Abstract: This line-commutated converter, in one form, has a pair of D.C. terminals for connection to a D.C. system and a pair of A.C. terminals for connection to an A.C. system. The converter comprises first, second, third, and fourth branches, each comprising the combination of a thyristor and a diode connected in inverse-parallel and an inductor connected in series with this combination. The first and fourth branches with a first node located therebetween are connected in series across the D.C. terminals; and the second and third branches with a second node located therebetween are also connected in series across the D.C. terminals. The nodes are effectively connected across the A.C. terminals. Controlled gating means simultaneously triggers the first and second branches into conduction at a controlled phase angle with respect to the A.C. system voltage and simultaneously triggers the third and fourth branches into conduction 180 degrees thereafter, repeating this sequence each cycle of the A.C. system voltage.

Abstract: Disclosed is an electrical power system adapted to receiving power from a source of alternating current, typically a small alternator, and supplying a direct current potential to a load. This power system includes two stages, the first stage comprising switchable rectifying devices such as silicon controlled rectifiers which interact with the impedance of the alternator or other source of alternating current power as a switching regulator to create an intermediate direct current potential.The second stage operates from this intermediate direct current potential to produce a slightly lower output voltage, and creates a more accurate regulation than is possible with the first stage alone, the second stage greatly reduces ripple and high frequency noise components contained on the output of the first regulator stage. The second stage serves as an active low pass filter tuned to a desired DC voltage.

Abstract: A voltage converter apparatus is provided to energize a first load and a second load from a power supply connected through an inverter and a coupling transformer, with the transformer having a first secondary winding energizing the first load with first voltage pulses having a variable width determined by the operational frequency of the inverter and having a second secondary winding energizing the second load with second voltage pulses having a variable width determined by a phase controlled switching apparatus responsive to one of the voltage and the current of the second voltage pulses.

Abstract: A load DC motor is supplied with a DC current through a converter principally consisting of thyristors controlled by an ON-state control signal. The load current is detected both as to the mean value and the variation in time thereof. The mean value of the load current is calculated based on the load current values detected at the time of the present On-signal and the preceding ON-signal. The difference between the reference value and the mean value of the load current is calculated, and the difference between this differential signal and the variation of the load current is further calculated, so that the timing for providing the ON-signal is calculated based on the resultant differential signal.

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 control circuit comprises a solid state controlled switch coupled to a terminal of the mains and a terminal of the load the supply voltage whereof has to be controlled, and a non controlled solid state switch operatively coupled to the solid state controlled switch for setting, in cooperation with resistive and capacitive elements, also supplied by the mains, the conduction time of the controlled switch in such a way as to adjust at predetermined maximum and minimum levels the load supply voltage.

Abstract: An automatic power reduction circuit having a single silicon controlled rectifier in one leg of a bridge rectifier which is gated off when a capacitor reaches a predetermined voltage level so as to switch automatically the bridge output from a full-wave rectifier to a half-wave rectifier. An auxiliary silicon controlled rectifier is also provided to facilitate the quick discharge of the capacitor so as to reset the circuit to its initial state, thereby allowing fast, repeated operations and preventing malfunctioning upon a loss of power.

Abstract: An improved method of electric fish trawling which utilizes the fright-reaction exhibited by fish exposed to an electric field is disclosed. The method utilizes a trawling net equipped with electrodes which emit DC pulses having a repetition rate of six cycles per second or less, a pulse duration of approximately one millisecond, and producing a field having a voltage gradient of one-hundred eighty volts per meter. A pulse generating circuit, which uses full-wave rectified single phase power or three phase, half-wave rectified power for a condenser discharge circuit is also provided.

Abstract: A switching voltage regulator is provided for coupling a source of AC potential to a DC load. Thyristor full wave rectifier means provide a source of DC potential which is connected to the load through an inductance in series with the load. The input of the inductance is shunted by a commutating diode which provides a path for the inductive current when the thyristor means are in the nonconducting phase of their operating cycle. Circuit means are provided to reverse bias the commutating diode in advance of each conduction cycle of the thyristor means. As a consequence, the level of RFI conducted to the AC power line is significantly reduced.

Abstract: 1.

Abstract: An electrical converter equipment for providing a d.c. voltage from an alternating current source. The converter has a unique operating cycle wherein a variable control angle is effected. The operating cycle for the converter comprises a series of half periods of the alternating current source. During different periods of time, the converter operates with different control angles. The control cycles comprise n periods of the input signal, where n is an odd number not less than three. During two half periods of a cycle, the control angle is varied. During two other half periods of the cycle, the converter operates at a fixed control angle. The half periods during which the converter is controlled with a variable control angle are time equidistant.

Abstract: In apparatus for supplying an electric power from a power source to a load through a thyristor, an ignition phase angle of which is controlled by a conduction control circuit through an ignition instruction generating circuit, there are provided a circuit for detecting voltage applied across the thyristor, another circuit for converting the detected voltage into a conduction completion phase angle, and still another circuit for displaying a conduction completion phase angle as well as the aforementioned ignition phase angle of the thyristor.

Abstract: A static electrical converter equipment has a plurality of controllable converter bridges connected to a common a.c. supply source. Control pulse devices supply control pulses to the controllable valves of the bridges. The converter equipment comprises members arranged to prevent a control pulse from being supplied to a valve in one of the bridges, for initiating a commutation in this bridge, until a corresponding commutation in another bridge is completed.

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 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: A power control circuit has a thyristor bridge interposed between a.c. buses connected to an a.c. power supply and a load. The firing circuit for the thyristors of the bridge includes a light actuated controlled rectifier for generating firing pulses. Two series connected resistor-capacitor pairs are connected in series across the a.c. buses. Taps intermediate the resistors and capacitors provide an energizing anode voltage to the controlled rectifier reduced with respect to the a.c. voltage in the buses. The voltage reducing and capacitive properties of the pairs render operation of the controlled rectifier immune to transient voltage spikes in the a.c. buses.

Abstract: An improved battery charger circuit for rapidly charing a battery by increasing the rate of battery charge acceptance through periodic battery discharge during the charging process includes a pair of first and second controlled rectifier circuits coupled to an AC source and adapted for coupling to a battery. The first controlled rectifier circuit is rendered conductive during the charging intervals to supply the battery with charge current from the AC source. The second controlled rectifier circuit is rendered conductive during battery discharge intervals to discharge the battery in a substantially lossless manner by conducting battery discharge current through the AC source, thus realizing a highly efficient battery charger.

Abstract: A static convertor with forced commutation is connected between an alternating voltage network and a direct voltage network. A filter is connected in parallel with a smoothing capacitor on the DC side of the convertor. The filter consists of the series-connection of an inductor, a filter capacitor and two controllable semiconductor valves that are connected in parallel in opposed relation. The natural frequency of the filter is higher than the product of the frequency of the alternating voltage network and the pulse number of the converter. The valves are made to carry current in time with the fundamental tone of the AC component present in the direct current of the convertor. In this way, the variations of the direct voltage of the convertor, caused by the AC direct current component, may be practically eliminated.

Abstract: A power converter apparatus for an a.c. electric rolling stock comprising two transformers, each including a primary winding and a plurality of secondary windings generating the same output voltages but having different internal reactances; a pair of phase-controlled bridge rectifier circuits, each being connected to one secondary winding of each transformer; and diode bridge rectifier circuits connected to the other secondary windings, wherein the windings connected to the pair of phase-controlled bridge rectifier circuits have different internal reactances, and the phase-controlled bridge rectifier circuits are simultaneously controlled, and when the maximum output voltages from the phase-controlled bridge rectifier circuits are reached, the output voltages from the diode bridge rectifier circuits (non-phase-controlled) are increased to their maximum values, then the output voltages from the phase-controlled bridge rectifier circuits are decreased to their minimum values.

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.