Abstract: A centralized voltage controller connected, via a communication network, to local voltage control units controlling voltage controllers, which are connected to a distribution line of a distribution system and control voltage of the distribution line, has: a voltage distribution determination unit calculating a controlled amount for each first voltage controller to be controlled among the plurality of voltage controllers, based on a measured value of voltage at each point of the distribution line; a tap position determination unit generating a command value to be given to each local voltage control unit based on the controlled amount; and a control state determination unit determining whether each voltage controller is a second voltage controller that fails to perform control according to the command value, and setting the voltage controllers except the second voltage controller to be the first voltage controller.

Abstract: The subject of the application is a power electronic tap changer module for transformer using power electronic elements connected to sections of a primary winding of the transformer. The power electronic tap changer module is equipped with valves having a pair of a thyristor or transistors connected with a controller and the valves are connected in series with the fuses, respectively. The module is equipped with an additional oversized tap line having an oversized valve rated for short circuit current, which valve is connected with an overvoltage triggering circuit. The oversized valve is equipped with a pair of thyristor or transistors connected with a thermally protected voltage suppressing device.

Abstract: There is provided a diagnosing device for an on-load tap changing apparatus of a transformer, which can diagnose the degradation degree of insulating oil at high accuracy by a relatively simple device configuration. A diagnosing device for an on-load tap changing apparatus has an insulating oil tank in which insulating oil is sealed, a changeover switching device that is disposed within the insulating oil tank and performs the tap changing operation of a tap winding, a tap selector that selects the tap position of the tap winding, and a polarity (transposition) changer that inverts the polarity of the tap winding or a winding connected to the tap winding. The diagnosing device includes an arc discharge light detector that detects arc discharge light that is emitted at changing the tap position of the tap selector. The degradation degree of the insulating oil is diagnosed based on the arc discharge light detected by the arc discharge light detector.

Abstract: The invention relates to a switching system for a tapped transformer with on-load tap changer wherein the tapped transformer comprises a main winding with a first main terminal; a coarse winding with a first coarse terminal and with a second coarse terminal; a control winding with a first control terminal; and an on-load tap changer that has a switch terminal and that interacts with the control winding; the switching system comprising a lead; a first switch subassembly comprising a first main fixed contact that can be connected to the first main terminal; a first coarse fixed contact that can be connected to the first coarse terminal; a first control fixed contact that can be connected to the first control terminal; a first switch fixed contact that can be connected to the first switch terminal; and a first movable bridge contact that is formed such that it electrically bridges or connects at least two fixed contacts of its switch subassembly in each stationary operating position of the switching system

Abstract: A permanent magnet drive on-load tap-changing switch including a changing switch circuit and a high-speed mechanism. The circuit includes structurally identical odd and even-numbered tap-changing switch circuits. The mechanism includes a traveling mechanism used for bearing a moving contactor, a moving magnet group connected with the traveling mechanism, and a fixed magnet group producing an attracting/repelling force with respect to the moving magnet group. The moving magnet group includes a first and second permanent magnet connected at homonymic magnetic poles. An exposed homonymic magnetic pole of the first and the second permanent magnet face directly the fixed magnet group. The fixed magnet group includes a rotating permanent magnet that rotates to change a force applied to the moving magnet group, allowing the moving contactors to either come into contact with or be separated from working contactors and dual-contact synchronous transition contactors.

Abstract: Disclosed is an on-load voltage regulation tap switch for a transformer, comprising a main switch group, a switch contact protection branch and a switch control circuit, wherein the main switch group comprises a plurality of switch contacts, one end of the switch group is connected to a corresponding transformer winding tap, and the other end of the switch group is connected in parallel and is then connected to a power source; the switch contact protection branch is a series circuit formed by a plurality of groups of diodes and auxiliary switch contacts, and is respectively connected to both ends of a corresponding main switch in parallel; and the switch control circuit is composed of a power source, a single chip microcomputer and a peripheral circuit, and controls all of the main switches and auxiliary switches to act in a certain time sequence to complete the switching of the transformer windings.

Abstract: There is provided a tap changer in which movable contacts rotate to be selectively connected to a plurality of taps. The tap changer includes a rotatable upper movable contact; a rotatable lower movable contact electrically connected to the upper movable contact; a driving shaft rotating the upper movable contact and the lower movable contact integrally; a single-type fixed contact including a single terminal connected to any one of a plurality of taps; and a dual-type fixed contact including a first terminal and a second terminal connected together to another of the plurality of taps. Since the upper movable contact and the lower movable contact are integrally rotated through the single driving shaft, the number of components and volume of the device may be reduced and an operation of the device may be facilitated.

Abstract: A system for operating an on-load tap changer (OLTC) includes a plurality of legs that include mechanical switches. At least one leg switches from a first to a second tap of the OLTC on receipt of a tap change signal. At least one mechanical switch is activated to establish an electrical connection between one of the first and the second tap and a power terminal of the OLTC. Further, the system includes semiconductor switches that are parallel to the mechanical switches and when activated electrically couple one of the first and the second tap and the power terminal. The system includes a processing unit that selectively activates and deactivates the mechanical and semiconductor switches in such a way that electrical contact is maintained between at least one of the taps and the power terminal during the transition of at least one leg from the first tap to the second tap.

Abstract: The invention relates to a method for reading data (120) from a document (104) using a reader (102), wherein the reader forms the primary side of a transformer (110), wherein the document has an electronic memory (118) for storing the data, processor means (114) for reading the data from the memory and at least one electrical load (128, 130, 132) which can be actuated by the processor means, wherein the document forms the secondary side of the transformer, and wherein the processor means and the at least one load are coupled to the secondary side for the purpose of supplying power, having the following steps: a primary-side voltage (U) is applied to the primary side for the purpose of injecting power into the secondary side, the at least one load is actuated by the processor means, as a result of which a time-variant secondary-side load is formed which prompts the primary-side voltage to undergo modulation, the modulation of the primary-side voltage is evaluated by the reader in order to execute read access f

Abstract: A reactive power compensator. The reactive power compensator includes a power transformer having an AC bus side and a compensator bus side, wherein the power transformer is connectable to an AC grid at the AC bus side. The reactive power compensator further includes a thyristor-switched capacitor and a thyristor-controlled reactor connected to the compensator bus side. The reactive power compensator includes a booster transformer connected in series with the power transformer and to the compensator bus side. The invention also relates to computer programs and computer program products.

Abstract: The invention relates to a stepping switch for voltage control, comprising semiconductor switch elements on a variable transformer having associated regulating windings. The stepping switch has a modular design, wherein each module comprises a respective sub-winding of the regulating winding which can be activated or deactivated by semiconductor switch elements.

Abstract: The invention relates to the arrangement of a stepping switch on a control transformer, wherein either only the mechanical contact system (8) of the stepping switch or also its load changeover switch (7) is or are arranged within the tank (1) of the transformer, under the transformer cover (4) and above the iron yoke (3).

Abstract: The invention relates to a tap changer for regulating voltage, comprising semiconductor switching elements on a regulating transformer having a regulating winding. The tap changer is modularly constructed, wherein each module comprises a sub-winding of the regulating winding that can be switched on or off by semiconductor switching elements.

Abstract: Regulation of a remote load center voltage from a local location of a voltage regulator and a voltage regulator control using voltage measurements from the remote load center obtained using a metering device at the load center in communication with the voltage regulator control. The metering device may obtain remote voltage information at the load center and communicate such to the voltage regulator control using a direct communications line, a wide area network, or the like. The communications may include electrical (e.g. copper cable), light (e.g. infrared over fiber optics), radio frequency, or the like. The voltage regulator control may be configured to use local measurements and a line drop compensation algorithm in the event that the remote voltage information becomes unavailable.

Abstract: The invention is for a 3-phase electronic tap changer commutation device to be utilized in electronic regulators, and more particularly to 3-phase alternating current (AC) electronic tap-changing voltage, current or phase correcting regulators. The present invention provides a specific transformer winding topology and commutation technique that improves performance and reduces cost compared to conventional methods.

Abstract: The invention relates to the arrangement of a stepping switch on a control transformer, wherein either only the mechanical contact system (8) of the stepping switch or also its load changeover switch (7) is or are arranged within the tank (1) of the transformer, under the transformer cover (4) and above the iron yoke (3).

Abstract: The invention provides a novel 3-phase electronic tap changer commutation and related device. In one embodiment, the invention includes firing a commutation silicon controlled rectifier (SCR), removing a gating signal from a first SCR connected to a first of the plurality of taps, firing a second SCR connected to a second of the plurality of taps, and removing a gating signal from the commutation SCR.

Abstract: A load tap changer includes a single mechanical switch that is movable to create, in a first position, a first conducting path between a first transformer tap and a load. When the switch is in a second position, the switch creates a second conducting path between a second transformer tap and the load. A first thyristor pair or other device creates a first alternate conducting path between the first transformer tap and the load when the switch is disengaged from the first position. A second thyristor pair or other device creates a second alternate conducting path between the second transformer tap and the load when the mechanical switch is disengaged from the second position. Each thyristor pair may be selectively triggered to provide a conducting path when voltage across either thyristor pair exceeds a predetermined level. A gate trigger circuit may be included for each thyristor pair, and a gate control circuit may control each of the gate trigger circuits.

Abstract: Apparatus for regulating an electric voltage in at least one of electric supply networks and consumer units. The apparatus includes a regulating transformer arranged between a network node and at least one end consumer. The regulating transformer utilizes a primary winding and a regulating winding which includes switchable partial windings and a high leakage impedance. The transformer conducts a nominal current. A transfer switch switches the partial windings of the regulating transformer. Adjacent tappings of the partial windings are adapted to short circuit such that, in an event of the short circuit, the high leakage impedance limits a ring current which results from the short circuit to an order of magnitude of the nominal current. The regulating transformer produces both an increase in voltage and a decrease in voltage at the end consumer. This abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

Abstract: A thyristor transformer has a mechanical tap selector and a diverter switch with thyristors. The tap selector is mounted in the oil-filled housing or tank of the transformer and the diverter switch is mounted in a separate housing laterally attached to the tank.

Abstract: A multi-line power flow transformer implements power flow control among multiple transmission lines in an n-phase power system. The transformer has an exciter unit with n primary windings. Each primary winding is on a core and receives a transmission voltage of a respective one of the phases of the power system. The transformer also has a series compensating unit for each transmission line. Each series compensating unit has n secondary windings on the core of each primary winding. Each secondary winding has a voltage induced thereon by the corresponding primary winding. For each phase, the secondary windings of the series compensating unit assigned to the phase are coupled in series to sum the induced voltages formed thereon. The summed voltage is a compensating voltage for the phase.

Abstract: The invention relates to a method for regulating the electrical voltage in electrical supply networks and/or consumer units and a device for carrying out said method. A regulating transformer (3) is inserted between a network node (1) in the supply network and/or consumer unit and at least one end user (2). The regulating transformer (3) comprises a high leakage impedance, which limits the ring current to the order of magnitude of the nominal current, in the case of a short-circuit between adjacent tappings (5) of the partial windings (4). The regulating transformer further comprises a transfer switch (7), to switch the partial windings (4).

Abstract: A power regulation system is coupled to an AC power source outputting an input voltage. The system has a first transformer to receive the input voltage and generate a control voltage. The system also has a second transformer that has a primary coil and a secondary coil. The primary coil and secondary coil of the second transformer are electromagnetically coupled to each other and so arranged that when the control voltage from the first transformer is applied to the primary coil, an output voltage is generated between a first end and a second end of the secondary coil, wherein the output voltage is substantially 180° out of phase from the input voltage so as to generate an effective voltage applied to the load, and wherein the effective voltage is less than the input voltage and substantially equals to the difference between the input voltage and the output voltage, resulting a reduction in power consumption of the load.

Abstract: A power regulation system is coupled to an AC power source outputting an input voltage. The system has a first transformer to receive the input voltage and generate a control voltage. The system also has a second transformer that has a primary coil and a secondary coil. The primary coil and secondary coil of the second transformer are electromagnetically coupled to each other and so arranged that when the control voltage from the first transformer is applied to the primary coil, an output voltage is generated between a first end and a second end of the secondary coil, wherein the output voltage is substantially 180° out of phase from the input voltage so as to generate an effective voltage applied to the load, and wherein the effective voltage is less than the input voltage and substantially equals to the difference between the input voltage and the output voltage, resulting a reduction in power consumption of the load.

Abstract: A power flow transformer implements power flow control in a transmission line of an n-phase power transmission system, where each phase of the power transmission system has a transmission voltage. The transformer has n secondary windings, where each secondary winding is on a core. The transformer also has n primary windings on the core of each secondary winding for a total of n2 primary windings, where one primary winding from each core is assigned to each phase. For each phase, the primary windings assigned to the phase are coupled in series, and the in-series primary windings receive the transmission voltage of the respective phase of the power transmission system. For each core, each primary winding thereon induces a voltage in the secondary thereon. The induced voltages are summed by the secondary to result in a summed induced voltage. Such summed induced voltage is a compensating voltage for a respective phase.

Abstract: A limited-angle power flow transformer implements power flow control in a transmission line of an n-phase power transmission system, where each phase of the power transmission system has a transmission voltage. The transformer has n primary windings, where each primary winding is on a core and receives the transmission voltage of a respective one of the phases of the power transmission system. The transformer also has m secondary windings on the core of each primary winding for a total of m*n secondary windings, where m is less than n. Each secondary winding has a voltage induced thereon by the corresponding primary winding. For each phase, m secondary windings are assigned to the phase. Each assigned secondary winding for the phase is from a different core. For all phases, the secondary windings are assigned from the cores in a balanced manner. For each phase, the secondary windings assigned to the phase are coupled in series for summing the induced voltages formed thereon.

Abstract: A regulator is provided for establishing asymmetrical voltage increase/decrease capability between an input node and an output node for enhanced regulation of either a voltage sag or a voltage swell within a utility system. The regulator includes an autotransformer having an input tap coupled to the input node of the regulator and an output tap coupled to the output node. The regulator further includes an electronic tap changer system coupled to the winding of the autotransformer. Together, the autotransformer and the electronic tap changer system provide the regulator with its asymmetrical voltage increase/decrease capability between the input node and the output node thereof. The regulator can be configured for voltage increase only, voltage decrease only, or both, provided an asymmetrical voltage increase/decrease capability is defined.

Abstract: In a method and a device for continuously adjusting, within a certain adjustment range, the turns ratio between the primary winding and the secondary winding of a power transformer provided with at least one regulating winding, a first tap is switched on during a portion of a cycle of the alternating voltage of the transformer and a second tap is switched on during another portion of the cycle of the alternating voltage. For this purpose, the device comprises electronic switches in the form of thyristors or transistors.

Abstract: A solid state voltage regulator and methods therefore are shown to include a transformer having a secondary coil, the secondary coil having a plurality of taps. A first solid state switch is connected between the regulator output and a first tap. The first switch need only have the capability of being turned on in response to a gate signal. A second solid state switch is connected between the regulator output and a second tap. The second switch has the capability of being turned on and turned off in response to gating signals. The output voltage resulting from the second tap is greater than the first tap. A controller, connected to the input, the output, the first switch and the second switch, senses the voltage present at the regulator input and output and generates gating signals in response to the sensed voltage. The voltage regulator may include several switches similar in construction and operation to the first switch.

Abstract: In an autotransformer of a single-phase three-wire system or a single-phase two-wire system, plural sets of main coils connected with input terminals are phase-wound on a single-phase core-type core, and further, between the ends of the main coils, plural sets of excitation coils mutually connected in series to wind on the single-phase core-type core are connected by plural combined connections. Further, plural sets of thyristors controlled ON/OFF by using the value measured by a voltage sensor connected to the aforementioned input terminals are provided between the aforementioned ends and the exciting coils. Therefore, the circuits are automatically changed in response to the increase and decrease of the input voltage, with a result that a load is not ill influenced so that the voltage value is always output within the predetermined range.

Abstract: A tap changing system for operation with a transformer and featuring a special group of gate-controlled electronic devices that operate as a circuit breaker and recloser such that, after half-cycle of short-circuit current, said special group is transferred to the OFF-state, whereby the tap changer winding is open circuited; the advantage being that only the special group of devices need be rated to sustain short-circuit conditions; a further feature is the concept of Discrete-Cycle Modulation (DCM) whereby tap voltage magnitudes are obtainable in increments intermediate the physical tap winding voltage magnitudes.

Abstract: An electric device is provided as an interface between a permanent power source and an electrical appliance for maintaining the appliance, or a component thereof, in an operative state during a momentary power failure. The electric circuit includes an auto-transformer for increasing the induced back electric magnetic field voltage which is present in the line voltage of the permanent power source during a momentary power outage. The auto-transformer increases the induced back electric magnetic field voltage to a voltage level which is sufficient to maintain digital clocks or other low power-requiring components incorporated in an electrical appliance in an operative state during a momentary power outage.

Abstract: A power switching circuit selectively connects an electrical load having first and second input connections to any one of a plurality of branch power circuits. Each branch circuit includes a first and second conductor defining a relative voltage therebetween. The power switching circuit includes a selector switch for selecting which of the branch circuits is to be connected to the load. A triac is electrically connected to the first conductor of each branch circuit and to the first input connection of the load for selectively electrically connecting one of the first conductors to the first input connection. A triac is electrically connected to the second conductor of each branch circuit and to the second input connection of the load for selectively electrically connecting one of the second conductors to the second input connection.

Abstract: A telephone line power utility circuit, in which direct-current power supplied through a telephone line-side is utilized as a power source for a line terminal device having a direct-current resistance, the telephone line power utility circuit including a DC-DC converter connected with the line terminal device for supplying the direct-current power to the line terminal device, the DC-DC converter having an input direct-current resistance; and a central processing unit (CPU), connected with the DC-DC converter, for obtaining a maximum input direct-current resistance of the DC-DC converter to increase the efficiency of receiving power of the DC-DC converter by allowing the direct-current resistance of the line terminal device, viewed from the telephone line-side, to satisfy a predetermined standard, controlling the duty ratio of the primary side switching element, and/or switching the taps of the primary side winding of the transformer of the DC-DC converter, such that the direct-current power supplied through t

Abstract: A controller for a line regulation device such as a voltage regulator is provided with an interface to a removable memory module. The memory module is preferably of the memory card type which can be carried by a field engineer in a clothing pocket. When the memory card is inserted into an externally accessible slot in the controller, its presence is signaled to the controllers microprocessor. In response, the microprocessor reads user selected control parameters which are entered via the controller's front panel. Depending on the control parameters, the microprocessor updates the programming code in its internal memory, executes the code stored in the memory card while it is present but does not update its internal memory, or dumps selected status information to the memory card so that it can be analyzed at a different location.

Abstract: Disclosed is an End-Turn Solid-State Switching (ETSS) transfomer tap which makes use of a high-speed solid-state switching network to select either the end-turn lead or one of a number of non-isolated taps on a transformer regulating winding, and connects the selected tap to, while disconnecting the previously selected tap from, a single output conductor carrying the transformer load current. ETSS effectively changes the reference to one of the possible taps interfaced to a solid-state switching network. The same transformer regulating winding connected to ETSS can also be connected in series with a slow-speed mechanically-switched tap-changer (LTC). ETSS selects one connection point on the regulating winding while LTC operation selects the second point. A difference voltage is produced, depending on the number of turns between the ETSS selected tap and the LTC selected tap. The sign of the difference in voltage depends on whether the ETSS selected tap is higher or lower than the LTC selected tap.

Abstract: A system for providing a constant current to airport or airfield signs is disclosed. The system receives input currents of varying amperages which also supply, and allow dimming of, runway or taxiway lights. According to various exemplary embodiments of the present invention, a high power factor is achieved which provides greater cost efficient operation of the signs.

Abstract: An apparatus and method for controlling tapchanger operation on voltage regulating transformers includes a plurality of transducers to obtain real time voltage, wattage and reactive power readings, along with status readings for breakers associated with circuitry. A processor includes components to convert the analog transducer signals to digital signals, and process those signals utilizing preprogrammed and predetermined multipliers. A processor can read programmable files that dictate operational set points and ranges of set points. The software program allows evaluation of the real time actual parameter readings in comparison with set point and range set points to issue instructions to change the tapchangers on the transformers to maintain control of and regulate the voltage from the transformer. Other features and advantages are described herein.

Abstract: An AC power regulator having a tap changer. The regulator comprises a transformer having taps and thyristors connected with the taps, respectively. The regulator further includes rectifiers, comparators having hysteresis and comparing the output signals from the rectifiers with a reference voltage, a priority processing circuit for selecting the signal to which the highest priority is given out of the output signals from the comparators, firing circuits for firing the thyristors, respectively, and zero voltage-detecting circuits for detecting the voltages between the terminals of the thyristors. When the detected voltages are all nonzero, the conducting thyristor is switched to the next thyristor.

Abstract: An electronic system connected to a power transmission line having a fluctuating load for automatically providing increments of voltage to the line to supplement voltage losses from the load by sequentially connecting tapes on the windings of a transformer in response to changes in line current.

Abstract: The invention relates to an arrangement in an on-load change-over switch of an on-load tap changer for uninterrupted switch-over of the regulating winding of a transformer. On-load change-over switching is usually accomplished using mechanical switching elements. Burning of contact and contamination of oil are disadvantageous. Furthermore, there are known constructions which use a combination of mechanical switching elements and thyristors for on-load change-over switching. The disadvantage of such arrangements is mainly the too great constructional expenditure for the control elements which are liable to breakdown.

Abstract: Described is a novel power supply for generating a constant d.c. voltage from a variable a.c. voltage supply line. The power supply includes a plurality of switch circuits which monitor voltage levels on respective secondary windings of a power transformer and as voltage levels change, one of the plurality of switch circuits is selected to charge a capacitor which provides a range of d.c. voltages which are processed to provide the constant d.c. voltage.

Abstract: An AC voltage regulator includes a transformer arrangement having a plurality of taps so that an input line voltage is passed to an output line with the output line voltage being determined by the nominal value of the input line voltage together with an amount contributed by the transformer. The device is switched by a network of relays one of which acts as a polarity reversal switch so that the voltage generated by the transformer is either added or subtracted to the nominal voltage. Further relays used in two series control the selection of the transformer tap. A transient suppression circuit uses a triac and resistor to communicate current from the input line to the output line with the triac gated into conduction on breaking of a relay contact. The input line voltage is measured by a comparator using a plurality of op-amps in series with the outputs therefrom passing through a logic circuit to control the relays.

Abstract: An uninterruptible power supply comprising a regulating transformer including output circuitry for connection to a load, first input circuitry for coupling a reserve AC voltage source to the regulating transformer and second input circuitry for coupling a primary AC voltage source to the regulating transformer, the second input circuitry comprising a plurality of winding taps, with each of the taps including a tap switch coupled to the primary AC voltage source.The uninterruptible power supply also includes a voltage control monitor for monitoring the voltage of the primary source and, if the voltage is outside a predetermined maximum allowable range, opening all of said tap switches to isolate the primary source from said transformer, and, if said voltage is within said predetermined maximum allowable range, selectively closing one of said tap switches so that the voltage at the load is held within a predetermined range.

Abstract: A tap-switching circuit for automatically controlling the output voltage of a multi-tap transformer in response to a varying input line voltage and/or system load current demand, includes voltage sensing circuitry in parallel with both the transformer voltage outputs and a voltage comparator for sensing changes in the system load demand requirements. A voltage reference is provided for automatically generating a pre-selected voltage reference level signal for the line and/or system load requirements. Voltage comparison circuitry is operatively connected with the voltage sensing circuitry for generating an enable signal whenever the input line voltage and/or system load current demand requirements sensed by the voltage sensing circuitry falls below the pre-selected voltage reference level signal.

Abstract: An arrangement for controlling an A.C. voltage supplied to a load, such as a fluorescent lamp emitting germicidal ultraviolet radiation in a water-purifying apparatus. The load is connected to the secondary winding of a transformer, the primary winding of which has a number of taps which are selectively connectable to an exterior A.C. voltage source. An electronic control device is arranged in dependence on the magnitude of the terminal voltage of the exterior A.C. voltage source to automatically connect that tap which causes the voltage applied to the load to be of a predetermined value.

Abstract: An electric transformer for supplying an adjustable electric magnitude, especially for regulating purposes, includes several modules having therebetween a binary progression relationship with respect to their power handling capabilities. Each module has a switching network for selectively rendering it operative or inoperative and, each module has at least one primary circuit input coil, the primary coils of each of the modules cooperating with one single secondary output circuit which is common to all of the modules. The switching network of each module being so connected as to allow the neutralization of the effect of the electronic induction of its respective primary coil or coils on the common secondary circuit, while maintaining the magnetic activity of the primary circuits.

Abstract: A thyristor circuit including a primary winding and at least one secondary winding and first and second bipolar thyristor switches connected across respective connections of the secondary winding. The first bipolar thyristor switch bridges N.sub.1 turns of the secondary winding, while the second bipolar thyristor switch bridges N.sub.2 turns of the secondary winding, wherein N.sub.2 is less than N.sub.1. The product between the maximum forward current of the second bipolar switch and the number of turns N.sub.2 is greater than the product between the latching current of the first bipolar thyristor switch and the number of turns N.sub.1 thereof. The second bipolar thyristor switch thus makes it possible to short-circuit the portion of the secondary winding bridged thereby, for operation as a switchable choke, e.g. in a reactive compensator, or as a variable power supply when supplemented by additional components.

Abstract: A voltage regulator using electronic control of two static switch circuits to permit tap changing without arcing at the switched electrical contacts, without interrupting the load current, and without inducing sizable circulating currents. As a mechanical drive connects a new tap to the auxiliary winding, current through the new winding is blocked by an auxiliary static switch. The drive next opens the main switch delivering current to the load. The opening of the main switch immediately allows the main static switch circuit to "turn on" to prevent arcing and load interruption until the next current zero. The main static switch control senses no current passing through the main switch and ceases gating, and therefore conduction, of the main static switch. Since neither the main static switch nor the auxiliary static switch is conducting current from the auxiliary winding, the load voltage begins dropping and the voltage across the auxiliary static switch begins rising.

Abstract: Two sources of alternating current, such as taps of a supply transformer, e selectively switchable across a load by means of two circuit branches each provided with a main switch and a collateral network in parallel therewith, this network comprising a series combination of a protective resistor, an ancillary switch and a pair of antiparallel thyristors. The gates of the thyristors of each pair are interconnected by a firing resistor in series with a disconnect switch; each gate, furthermore, is connected to its own cathode through a reverse-poled diode which enables the ignition of the opposite thyristor upon closure of the disconnect switch when the proper polarity of the source voltage appears across the network in the closed state of the associated ancillary switch.