EP0375687B1 - Thyristor on-load change-over switch - Google Patents

Thyristor on-load change-over switch Download PDF

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Publication number
EP0375687B1
EP0375687B1 EP88905150A EP88905150A EP0375687B1 EP 0375687 B1 EP0375687 B1 EP 0375687B1 EP 88905150 A EP88905150 A EP 88905150A EP 88905150 A EP88905150 A EP 88905150A EP 0375687 B1 EP0375687 B1 EP 0375687B1
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Prior art keywords
load
change
contact
switch
over
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German (de)
French (fr)
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EP0375687A1 (en
EP0375687B2 (en
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Ernst Sonntagbauer
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Cessione elin Oltc Stufenschalter fur Transfo GmbH
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Andritz Hydro GmbH Austria
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/0005—Tap change devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F29/00—Variable transformers or inductances not covered by group H01F21/00
    • H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
    • H01F29/04—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings having provision for tap-changing without interrupting the load current
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/54—Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere
    • H01H9/548—Electromechanical and static switch connected in series

Definitions

  • the invention relates to an arrangement in a load changeover switch of a tap changer for uninterrupted switching of the control winding of a transformer, the load current via a low or higher winding tap of a control stage of a control winding and via a connection of at least two selector contacts and two permanent contacts with a common one Derivation is feasible, and the changeover from the lower to the higher winding tapping or vice versa takes place via a first changeover switch in such a way that the load current is briefly transferred to a relief circuit which is arranged between the root connection of this first changeover switch and the common discharge line, and whereby one of the two contacts of the first changeover switch is connected to the connection of a selector contact with a permanent contact.
  • the uninterrupted load switching is usually carried out under voltage using mechanical switching elements.
  • the control winding to be switched has taps, which are connected to a selector, which can be connected to the common derivative via the diverter switch.
  • Switching always takes place between adjacent taps, i.e. one level at a time.
  • the desired tap with the voter is preselected.
  • the diverter switch then switches the current from the selected to the preselected tap, with intermittent switching resistors. In the two end positions, the switching resistances are not loaded because they are bridged by the main contacts of the diverter switch.
  • the selector and diverter switch are usually housed in the transformer tank, the diverter switch being in its own vat, the oil filling of which is separated from that of the transformer by seals.
  • the arrangement described in GB-A-1 399 528 consists of at least two selector contacts and two permanent contacts, a circuit breaker and a relief circuit with two anti-parallel thyristors, two ignition diodes and a thyristor control contact.
  • the selector consists of two single-pole changeover switches that are not moved at the same time, the changeover contacts of one changeover switch being connected to the changeover contacts of the other changeover switch and being connected to a control stage of a control winding.
  • One conductive connection leads directly from the root connections of the two selectors, the other to the root connection of the two permanent contacts via the switching resistor.
  • the permanent contacts short the thyristor circuit.
  • Both the permanent contacts and the thyristor control contact are rigidly connected to a drive shaft.
  • the thyristor group When switching on, the thyristor group first takes over the load current. Then this is switched off and the load current is forced onto the current path of the transition resistor. The next control stage is preselected by moving one of the two selector contacts to the desired tap. Now the thyristor circuit switches the load current to this preselected tap. While the load current flows through one selector contact, the second selector contact carries the equalizing current.
  • the thyristor group is loaded with the sum of the load current and the compensation current.
  • both voters are tapped; therefore, with the same number of contacts, only half of the taps can be accommodated on the electorate.
  • the selector contacts are integrated into the switching process so that their slow movement results in an increase in the time load of the thyristors by at least one order of magnitude.
  • the load current is fed to the control stage of a control winding via winding taps and to a common derivation via selector and permanent contacts.
  • a thyristor circuit with anti-parallel thyristors is arranged here.
  • the two thyristor circuits are connected to the common lead via a separate contact.
  • the switching sequence is controlled by a logic circuit.
  • the sequence is such that the load current is always switched by the thyristors and, depending on the switching process to be carried out, is either subsequently commutated to the permanent contact or has previously been commutated from the permanent contact to the thyristors.
  • Another disadvantage is the influence of the high voltage on the electronic part. There is also the risk that the magnetic fields of the transformer windings will trigger misfires of the thyristors.
  • Each tap of the transformer control winding has a fixed conductive connection to a pair of antiparallel connected thyristors, the outgoers of which are connected to the common derivative.
  • the thyristors are switched via a control circuit of the transformer. Switching from one stage to another is carried out by switching the selected thyristor pair from the conductive to the non-conductive, and the preselected from the non-conductive to the conductive switching state.
  • a disadvantage of this arrangement is the high technical complexity and the susceptibility to malfunction of the electronic components required for control.
  • DE-AS 23 27 610 describes an embodiment which consists of two load branches, each of which connects a tap of the control winding with a common derivative.
  • a selector and an isolating contact as well as a parallel connection, consisting of a thyristor and a permanent contact, are in series in each load branch.
  • the thyristors are polarized in opposite directions.
  • a current branch is arranged between the two load branches, which can be connected in parallel to one of the two load branches via a changeover switch.
  • This current branch consists of two antiparallel connected diodes, the input of a voltage detection and ignition device is in parallel.
  • the isolating contact and the permanent contact assigned to the first tap or the first load branch are closed.
  • the additional current branch is connected in parallel to this load branch via the synchronous switch.
  • the load current is commutated to the additional current branch.
  • the first thyristor is ignited and the changeover pulse for the synchronous changeover switch is released at the same time.
  • the synchronous changeover switch lifts from the first changeover contact, the current commutates to the first thyristor.
  • the current changes from the first to the second tap and thus via the second selector contact to the second thyristor.
  • This embodiment has the disadvantage that the switchover cannot be guaranteed for all operating cases and switching times, since it is to take place at zero current, which can only be measured by complicated and fault-prone electronic devices.
  • a load switchover is also described in US Pat. No. 3,662,253, two vacuum switches being arranged between a common lead and two selector contacts. Furthermore, a relief circuit is provided, which lies between the common derivation and - by using a changeover switch - one selector contact each and is designed so that it can be connected in parallel to one of the two vacuum switches.
  • the relief circuit contains a series connection of a current limiting resistor with a semiconductor switch.
  • a bypass circuit with high impedance is provided for this semiconductor switch in order to limit occurring current increases.
  • the circuit of the bypass circuit is coupled to the primary winding of a current transformer, the secondary winding of which is fed to a grid control device.
  • the grid control unit contains control elements which use the secondary current rise of the current transformer integrated in the bypass circuit.
  • the taps are switched under load, with the relief circuit interposed, during the interdependent switch-on and switch-off movements of the vacuum switches.
  • This US-A-3 662 253 also proposes a more complex system for switching the taps of regulating transformers, in which in turn two vacuum switches are located between the common discharge line and the selector contacts. There is also an outlet here circuit between the common discharge line and a changeover switch arranged in such a way that the relief circuit can be placed parallel to one of the two vacuum switches.
  • the relief circuit consists of a series connection of a semiconductor switch with an ohmic resistor; this series circuit is connected in parallel to a semiconductor switch. To prevent a voltage rise during the switching processes, a voltage limiting circuit is provided in parallel to the semiconductor switch of the series circuit.
  • the connecting lines between the two vacuum switches and the common derivative, as well as the connecting line between the voltage limiting circuit and the common derivative, are each coupled to the primary winding of an associated one of three current transformers.
  • the secondary windings of these current transformers are each connected to an assigned one of three grid control units, which are responsible for the timely ignition of the semiconductor switches of the relief circuit.
  • a corresponding ignition setting ensures that the load current flows through the semiconductor switches during the opening and closing of the vacuum switches, so that an arc is prevented.
  • the object of the invention is therefore to provide an arrangement in a load changeover switch of a tap changer for the uninterrupted switching of the control winding of a transformer of the type mentioned at the outset, which avoids the disadvantages of the known arrangements and the voltage and current loading of the thyristors during the switching process on one Minimum holds.
  • the relief circuit consists of a second changeover switch and a thyristor circuit in series with antiparallel connected thyristors, and that a tripping resistor is connected to the common derivative via a bypass switch, and that the one changeover contact of the second changeover switch is direct and the other changeover contact of this second changeover switch is connected to the root connection of the first changeover switch via the transition resistor.
  • the mechanical switching elements used in the known diverter switch and the switchover resistances can be used.
  • the two permanent contacts are a further changeover contact.
  • FIG. 1 represents the diverter switch according to the invention
  • FIGS. 2 and 3 are the associated flowcharts.
  • FIG. 1 shows a control stage 13 of a control winding, the load current of which can be fed to a common derivative 16 via a lower or higher winding tapping 11, 12 and at least two selector contacts 14, 15 and two permanent contacts 9, 10.
  • the changeover from the lower to the higher winding tapping or vice versa takes place via a changeover switch 5, the load current passing briefly to a relief circuit 17 which is arranged between the root connection 6 of the changeover switch 5 and the common derivative 16.
  • One of each of the two contacts 7, 8 of the changeover switch 5 is connected to the connection of the selector contact 14, 15 to the permanent contact 9, 10.
  • the relief circuit 17 consists of a changeover switch 18 and a series thyristor circuit 2 with antiparallel connected thyristors 2a, 2b.
  • a switching resistor 4 is connected to the common derivative 16 via a bypass switch 23.
  • One changeover contact 20 of the changeover switch 18 is directly connected, the other changeover contact 21 is connected to the root connection 6 of the changeover switch 5 via the switching resistor 4.
  • the switching times for the ignition of the thyristors 2a, 2b are offset asymmetrically.
  • step tap 11 a switchover from step tap 11 to step tap 12 of control stage 13 of a control winding is described in steps.
  • the links - The designations on the side in FIG. 2 correspond to the switches or thyristors and contacts in FIG. 1.
  • 11 _ 12 means the switching direction from tap 11 to 12.
  • the first of the two fields which relate to the thyristor circuit 2 shows Field the duration of the ignition pulses, the second field the duration of the current flow through the thyristors.

Abstract

PCT No. PCT/AT88/00045 Sec. 371 Date Dec. 6, 1989 Sec. 102(e) Date Dec. 6, 1989 PCT Filed Jun. 14, 1988 PCT Pub. No. WO88/10502 PCT Pub. Date Dec. 29, 1988.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. According to the invention, the on-load current is supplied to a common output line via a lower winding tap or a higher winding tap of a regulating stage of a regulating winding, and through at least two selector contacts and two permanent contacts whereby the switch-over from the lower to the higher winding tap, and vice versa, is effected via a change-over switch which briefly switches the on-load current to a load relief circuit which is arranged between the root connection of the change-over switch and the common output line. The discharge circuit could comprise, for example, two thyristor circuits, the thyristors of which are connected in antiparallel, one of these thyristor circuits being connected in series with a transition resistor.

Description

Die Erfindung betrifft eine Anordnung bei ei - nem Lastumschalter eines Stufenschalters zum unterbrechungslosen Umschalten der Regelwicklung eines Transformators, wobei-der Laststrom über eine niedere oder höhere Wicklungsanzapfung einer Regelstufe einer Regelwicklung und über eine Verbindung von mindestens zwei Wäh - lerkontakten und zwei Dauerkontakten mit einer gemeinsamen Ableitung führbar ist, und wobei die Umschaltung von der niederen auf die höhere Wicklungsanzapfung oder umgekehrt über einen ersten Umschalter derart erfolgt, daß der Laststrom kurzzeitig auf einen Entlastungskreis übergeht, der zwischen dem Wurzelanschluß dieses ersten Um - schalters und der gemeinsamen Ableitung angeordnet ist, und wobei jeweils einer der beiden Kontakte des ersten Umschalters an die Verbin - dung eines Wählerkontaktes mit einem Dauerkon - takt gelegt ist.The invention relates to an arrangement in a load changeover switch of a tap changer for uninterrupted switching of the control winding of a transformer, the load current via a low or higher winding tap of a control stage of a control winding and via a connection of at least two selector contacts and two permanent contacts with a common one Derivation is feasible, and the changeover from the lower to the higher winding tapping or vice versa takes place via a first changeover switch in such a way that the load current is briefly transferred to a relief circuit which is arranged between the root connection of this first changeover switch and the common discharge line, and whereby one of the two contacts of the first changeover switch is connected to the connection of a selector contact with a permanent contact.

Üblicherweise wird bei Stufentransformatoren die unterbrechungslose Lastumschaltung unter Spannung mit mechanischen Schaltelementen durchgeführt. Die zu schaltende Regelwicklung besitzt Anzapfungen, die mit einem Wähler verbunden sind, welcher sie wahlweise über den Lastumschalter an die gemeinsame Ableitung legt.In the case of step transformers, the uninterrupted load switching is usually carried out under voltage using mechanical switching elements. The control winding to be switched has taps, which are connected to a selector, which can be connected to the common derivative via the diverter switch.

Die Umschaltung erfolgt immer zwischen benachbarten Anzapfungen, also um jeweils eine Stufe. Zu diesem Zweck wird zuerst die gewünschte Anzapfung mit dem Wähler vorgewählt. Danach führt der Lastumschalter, unter zeitweiliger Zwischenschaltung von Überschaltwiderständen, die Umschaltung des Stromes von der gewählten auf die vorgewählte Anzapfung durch. In den bei - den Endstellungen sind die Überschaltwiderstände, da sie durch die Hauptkontakte des Lastumschal - ters überbrückt sind, nicht belastet.Switching always takes place between adjacent taps, i.e. one level at a time. For this purpose, the desired tap with the voter is preselected. The diverter switch then switches the current from the selected to the preselected tap, with intermittent switching resistors. In the two end positions, the switching resistances are not loaded because they are bridged by the main contacts of the diverter switch.

Wähler und Lastumschalter sind üblicherweise im Trafokessel untergebracht, wobei sich der Lastumschalter in einem eigenen Bottich befindet, dessen Ölfüllung von der des Trafos durch Dich - tungen getrennt ist.The selector and diverter switch are usually housed in the transformer tank, the diverter switch being in its own vat, the oil filling of which is separated from that of the transformer by seals.

Von Nachteil ist dabei der beim Umschalten auftretende Abbrand der Kontakte und die Verruß - ung des Öles durch die beim Schalten auftretenden Lichtbögen. Es müssen daher zur Gewährleistung eines einwandfreien Betriebes Kontakte und Öl nach einer bestimmten Schaltzahl gewechselt werden, so daß es durch die damit bedingte Abschaltung des Trafos zu Betriebsunterbrechungen kommt.Disadvantages here are the erosion of the contacts that occurs when switching and the sooting of the oil due to the arcing that occurs during switching. To ensure proper operation, contacts and oil must therefore be changed after a certain number of operations, so that the switch-off of the transformer caused by this leads to interruptions in operation.

Weiters sind Ausführungen bekannt, bei denen die Lastumschaltung mit einer Kombination von mechanischen Schaltelementen und Thyristoren durchgeführt wird. Aus der GB-A-1 1 399 528 ist eine solche Kombination ersichtlich.Furthermore, designs are known in which the load switching is carried out using a combination of mechanical switching elements and thyristors. Such a combination can be seen from GB-A-1 1 399 528.

Die in der GB-A-1 399 528 beschriebene Anordnung besteht aus mindestens zwei Wähler-und zwei Dauerkontakten, einem Überschaltwiderstand sowie einem Entlastungskreis mit zwei anti - parallelgeschalteten Thyristoren, zwei Zünddioden und einem Thyristor-Ansteuerungskontakt.The arrangement described in GB-A-1 399 528 consists of at least two selector contacts and two permanent contacts, a circuit breaker and a relief circuit with two anti-parallel thyristors, two ignition diodes and a thyristor control contact.

Der Wähler besteht aus zwei nicht gleichzeitig bewegten einpoligen Umschaltern, wobei die Um - schaltkontakte des einen Umschalters mit den Umschaltkontakten des anderen Umschalters ver - bunden und an jeweils eine Anzapfung einer Regelstufe einer Regelwicklung gelegt sind.The selector consists of two single-pole changeover switches that are not moved at the same time, the changeover contacts of one changeover switch being connected to the changeover contacts of the other changeover switch and being connected to a control stage of a control winding.

Von den Wurzelanschlüssen der beiden Wäh - ler führt eine leitende Verbindung direkt, die andere über den Überschaltwiderstand zu je einem Wurzelanschluß der beiden Dauerkontakte.One conductive connection leads directly from the root connections of the two selectors, the other to the root connection of the two permanent contacts via the switching resistor.

Über die Wähler- und Dauerkontakte erfolgt, je nach Schaltstellung direkt oder über den Thyri - storkreis, eine Verbindung zu einer gemeinsamen Ableitung.Via the selector and permanent contacts, depending on the switching position, there is a connection to a common derivation, or via the thyristor circuit.

In der Mittelstellung schließen die Dauerkon - takte den Thyristorkreis kurz. Sowohl die Dauerkontakte als auch der Thyristor-Ansteuerungskontakt sind starr mit einer Antriebswelle verbun - den.In the middle position, the permanent contacts short the thyristor circuit. Both the permanent contacts and the thyristor control contact are rigidly connected to a drive shaft.

Beim Einschaltvorgang übernimmt zuerst die Thyristorgruppe den Laststrom. Dann wird diese abgeschaltet und dadurch der Laststrom auf den Strompfad des Überschaltwiderstandes gezwungen. Die Vorwahl der nächsten Regelstufe erfolgt dadurch, daß einer der beiden Wählerkontakte zur gewünschten Anzapfung bewegt wird. Nun schaltet der Thyristorkreis den Laststrom auf diese vorgewählte Anzapfung. Während über einen Wählerkontakt der Laststrom fließt, führt der zweite Wäh - lerkontakt den Ausgleichsstrom.When switching on, the thyristor group first takes over the load current. Then this is switched off and the load current is forced onto the current path of the transition resistor. The next control stage is preselected by moving one of the two selector contacts to the desired tap. Now the thyristor circuit switches the load current to this preselected tap. While the load current flows through one selector contact, the second selector contact carries the equalizing current.

Aus dieser Anordnung ergeben sich mehrere Nachteile. Beim Umschaltvorgang wird die Thyri - storgruppe mit der Summe aus Laststrom und Ausgleichsstrom belastet. In der Endstellung liegen beide Wähler auf einer Anzapfung; daher kann man, bei gleicher Kontaktzahl, nur die Hälfte der Anzapfungen am Wählerumfang unterbringen. Zu - dem sind die Wählerkontakte in den Umschaltvorgang so integriert, daß aus ihrer langsamen Bewegung eine Erhöhung der zeitlichen Belastung der Thyristoren um mindestens eine Größenord - nung resultiert.There are several disadvantages to this arrangement. During the switchover process, the thyristor group is loaded with the sum of the load current and the compensation current. In the end position, both voters are tapped; therefore, with the same number of contacts, only half of the taps can be accommodated on the electorate. In addition, the selector contacts are integrated into the switching process so that their slow movement results in an increase in the time load of the thyristors by at least one order of magnitude.

Eine andere Anordnung zur Lastumschaltung mit mechanischen Schaltelementen und Thyristoren zeigt die DE - PS 2 104 076.Another arrangement for load switching with mechanical switching elements and thyristors is shown in DE - PS 2 104 076.

Auch hier wird der Laststrom über Wicklungsanzapfungen der Regelstufe einer Regelwicklung und über Wähler - und Dauerkontakte einer gemeinsamen Ableitung zugeführt. Statt der üblichen zwei Überschaltwiderstände ist hier jeweils ein Thyristorkreis mit antiparallelgeschalteten Thyri - storen angeordnet. Die beiden Thyristorkreise sind über jeweils einen Trennkontakt mit der gemein - samen Ableitung verbunden.Here, too, the load current is fed to the control stage of a control winding via winding taps and to a common derivation via selector and permanent contacts. Instead of the usual two contact resistors, a thyristor circuit with anti-parallel thyristors is arranged here. The two thyristor circuits are connected to the common lead via a separate contact.

Der Schaltablauf wird durch eine Logikschal - tung gesteuert. Der Ablauf erfolgt derart, daß der Laststrom stets von den Thyristoren geschaltet und, abhängig vom jeweils durchzuführenden Schaltvorgang, entweder anschließend auf den Dauerkontakt kommutiert wird, oder vorher vom Dauerkontakt auf die Thyristoren kommutiert wor - den ist.The switching sequence is controlled by a logic circuit. The sequence is such that the load current is always switched by the thyristors and, depending on the switching process to be carried out, is either subsequently commutated to the permanent contact or has previously been commutated from the permanent contact to the thyristors.

Nachteilig dabei ist der große Aufwand an den zur Steuerung benötigten elektronischen Bauteilen und deren Störanfälligkeit.The disadvantage here is the great expense of the electronic components required for control and their susceptibility to malfunction.

Ein weiterer Nachteil ist die Beeinflussung des Elektronikteils durch die Hochspannung. Zudem besteht die Gefahr, daß die magnetischen Felder der Trafowicklungen Fehlzündungen der Thyristoren auslösen.Another disadvantage is the influence of the high voltage on the electronic part. There is also the risk that the magnetic fields of the transformer windings will trigger misfires of the thyristors.

In der GB - PS 1 007 496 ist eine weitere Anordnung zur Lastumschaltung beschrieben. Hierbei besteht von jeder Anzapfung der Transformator-Regelwicklung eine feste leitende Verbindung zu jeweils einem Paar antiparallelgeschalteter Thyristoren, deren Abgänge mit der gemeinsamen Ableitung verbunden sind.Another arrangement for load switching is described in GB-PS 1 007 496. Each tap of the transformer control winding has a fixed conductive connection to a pair of antiparallel connected thyristors, the outgoers of which are connected to the common derivative.

Über einen Steuerstromkreis des Transformators werden die Thyristoren geschaltet. Die Um - schaltung von einer Stufe auf eine andere wird durchgeführt, indem das gewählte Thyristorpaar vom leitenden in den nichtleitenden, und das vorgewählte vom nichtleitenden in den leitenden Schaltzustand gesetzt wird.The thyristors are switched via a control circuit of the transformer. Switching from one stage to another is carried out by switching the selected thyristor pair from the conductive to the non-conductive, and the preselected from the non-conductive to the conductive switching state.

Nachteilig bei dieser Anordnung ist der hohe technische Aufwand und die Störanfälligkeit der zur Steuerung nötigen elektronischen Bauteile.A disadvantage of this arrangement is the high technical complexity and the susceptibility to malfunction of the electronic components required for control.

In der DE-AS 23 27 610 ist eine Ausführung beschrieben, die aus zwei Lastzweigen besteht, welche jeweils eine Anzapfung der Regelwicklung mit einer gemeinsamen Ableitung verbinden. In jedem Lastzweig liegen ein Wähler- und ein Trennkontakt sowie eine Parallelschaltung, bestehend aus einem Thyristor und einem Dauerkontakt, in Serie. Die Thyristoren sind entgegengesetzt gepolt.DE-AS 23 27 610 describes an embodiment which consists of two load branches, each of which connects a tap of the control winding with a common derivative. A selector and an isolating contact as well as a parallel connection, consisting of a thyristor and a permanent contact, are in series in each load branch. The thyristors are polarized in opposite directions.

Zwischen den beiden Lastzweigen ist ein Stromzweig angeordnet, der über einen Umschalter jeweils einem der beiden Lastzweige parallelge - schaltet werden kann. Dieser Stromzweig besteht aus zwei antiparallelgeschalteten Dioden, denen der Eingang eines Spannungserfassungs- und Zündgerätes parallel liegt.A current branch is arranged between the two load branches, which can be connected in parallel to one of the two load branches via a changeover switch. This current branch consists of two antiparallel connected diodes, the input of a voltage detection and ignition device is in parallel.

Bei dieser Ausführung sind zu Beginn der Umschaltung von einer ersten auf eine zweite An - zapfung der der ersten Anzapfung bzw. dem ersten Lastzweig zugeordnete Trennkontakt und Dauerkontakt geschlossen. Der zusätzliche Stromzweig ist über den Synchron - Umschalter diesem Last - zweig parallelgeschaltet.In this embodiment, at the start of the switchover from a first to a second tap, the isolating contact and the permanent contact assigned to the first tap or the first load branch are closed. The additional current branch is connected in parallel to this load branch via the synchronous switch.

Durch Öffnen des Dauerkontaktes im ersten Lastzweig wird der Laststrom auf den zusätzlichen Stromzweig kommutiert. Nach dem Schließen des Trennkontaktes im zweiten Lastzweig wird der er - ste Thyristor gezündet und gleichzeitig der Umschaltimpuls für den Synchron - Umschalter abge - setzt. Der Synchron - Umschalter hebt vom ersten Umschaltkontakt ab, der Strom kommutiert auf den ersten Thyristor. Durch Sperrung des ersten und Zündung des zweiten Thyristors im zweiten Lastzweig wechselt der Strom von der ersten auf die zweite Anzapfung und somit über den zweiten Wählerkontakt auf den zweiten Thyristor.By opening the permanent contact in the first load branch, the load current is commutated to the additional current branch. After the isolating contact in the second load branch is closed, the first thyristor is ignited and the changeover pulse for the synchronous changeover switch is released at the same time. The synchronous changeover switch lifts from the first changeover contact, the current commutates to the first thyristor. By blocking the first and igniting the second thyristor in the second load branch, the current changes from the first to the second tap and thus via the second selector contact to the second thyristor.

Inzwischen ist der Synchron - Umschalter am zweiten Umschaltkontakt angelangt, der Laststrom wird vom zusätzlichen Stromzweig übernommen. Mit dem Öffnen des Trennkontaktes im ersten und dem Schließen des Dauerkontaktes im zweiten Lastzweig ist der Umschaltvorgang beendet.In the meantime the synchronous changeover switch has reached the second changeover contact, the load current is taken over by the additional current branch. The switching process ends when the isolating contact in the first and the permanent contact in the second load branch is closed.

Diese Ausführung hat den Nachteil, daß die Umschaltung nicht für alle Betriebsfälle und Schaltzeitpunkte gewährleistet werden kann, da sie im Stromnulldurchgang erfolgen soll, welcher erst durch komplizierte und störanfällige elektronische Geräte zu messen ist.This embodiment has the disadvantage that the switchover cannot be guaranteed for all operating cases and switching times, since it is to take place at zero current, which can only be measured by complicated and fault-prone electronic devices.

Auch in der US-A-3 3 662 253 ist eine Lastumschaltung beschrieben, wobei zwischen einer gemeinsamen Ableitung und zwei Wählerkontakten zwei Vakuumschalter angeordnet sind. Weiters ist ein Entlastungskreis vorgesehen, welcher zwischen der gemeinsamen Ableitung sowie - durch Verwendung eines Umschalters - jeweils einem Wählerkontakt liegt und so ausgeführt ist, daß er zu jeweils einem der beiden Vakuumschaltern paral - lelgeschaltet werden kann.A load switchover is also described in US Pat. No. 3,662,253, two vacuum switches being arranged between a common lead and two selector contacts. Furthermore, a relief circuit is provided, which lies between the common derivation and - by using a changeover switch - one selector contact each and is designed so that it can be connected in parallel to one of the two vacuum switches.

Der Entlastungskreis enthält eine Serienschal - tung eines strombegrenzenden Widerstandes mit einem Halbleiterschalter. Für diesen Halbleiterschalter ist ein Bypasskreis mit großer Impedanz vorgesehen, um auftretende Stromanstiege zu begrenzen. Der Kreis des Bypasskreises ist mit der Primärwicklung eines Stromwandlers gekoppelt, dessen Sekundärwicklung einem Gittersteuergerät zugeführt ist. Das Gittersteuergerät beinhaltet Steuerglieder, welche den sekundären Stromanstieg des im Kreis des Bypasskreises eingebrach - ten Stromwandlers ausnützen.The relief circuit contains a series connection of a current limiting resistor with a semiconductor switch. A bypass circuit with high impedance is provided for this semiconductor switch in order to limit occurring current increases. The circuit of the bypass circuit is coupled to the primary winding of a current transformer, the secondary winding of which is fed to a grid control device. The grid control unit contains control elements which use the secondary current rise of the current transformer integrated in the bypass circuit.

Das Umschalten der Anzapfungen unter Last erfolgt, unter Zwischenschaltung des Entlastungs - kreises, während der voneinander abhängigen Einschalt - bzw. Ausschaltbewegungen der Vaku - umschalter.The taps are switched under load, with the relief circuit interposed, during the interdependent switch-on and switch-off movements of the vacuum switches.

In dieser US-A-3 662 253 wird auch ein aufwendigeres System zum Umschalten der An - zapfungen von Regeltransformatoren vorgeschlagen, bei welchem wiederum zwei Vakuumschalter zwischen der gemeinsamen Ableitung und den Wählerkontakten liegen. Auch hier ist ein Entlastungskreis zwischen der gemeinsamen Ableitung und einem Umschalter derart angeordnet, daß der Entlastungskreis parallel zu jeweils einem der bei - den Vakuumschalter gelegt werden kann.This US-A-3 662 253 also proposes a more complex system for switching the taps of regulating transformers, in which in turn two vacuum switches are located between the common discharge line and the selector contacts. There is also an outlet here circuit between the common discharge line and a changeover switch arranged in such a way that the relief circuit can be placed parallel to one of the two vacuum switches.

Der Entlastungskreis besteht aus einer Serienschaltung eines Halbleiterschalters mit einem ohmschen Widerstand; diese Serienschaltung ist einem Halbleiterschalter parallelgeschaltet. Zur Verhinderung eines Spannungsanstieges während der Umschaltvorgänge ist, parallel zum Halbleiterschalter der Serienschaltung, ein Spannungsbegrenzungskreis vorgesehen.The relief circuit consists of a series connection of a semiconductor switch with an ohmic resistor; this series circuit is connected in parallel to a semiconductor switch. To prevent a voltage rise during the switching processes, a voltage limiting circuit is provided in parallel to the semiconductor switch of the series circuit.

Die Verbindungsleitungen zwischen den beiden Vakuumschaltern und der gemeinsamen Ableitung, sowie die Verbindungsleitung zwischen dem Spannungsbegrenzungskreis und der gemeinsamen Ableitung sind jeweils mit der Primärwicklung eines zugeordneten von drei Stromwandlern gekoppelt. Die Sekundärwicklungen dieser Strom - wandler sind mit jeweils einem zugeordneten von drei Gittersteuergeräten verbunden, denen die zeitgerechte Zündung der Halbleiterschalter des Entlastungskreises obliegt. Durch entsprechende Zündeinstellung wird erreicht, daß während des Öffnens und Schließens der Vakuumschalter der Laststrom über die Halbleiterschalter fließt, so daß ein Lichtbogen verhindert wird.The connecting lines between the two vacuum switches and the common derivative, as well as the connecting line between the voltage limiting circuit and the common derivative, are each coupled to the primary winding of an associated one of three current transformers. The secondary windings of these current transformers are each connected to an assigned one of three grid control units, which are responsible for the timely ignition of the semiconductor switches of the relief circuit. A corresponding ignition setting ensures that the load current flows through the semiconductor switches during the opening and closing of the vacuum switches, so that an arc is prevented.

Der Nachteil der in der US-A-3 662 253 vorgeschlagenen Schaltungsanordnungen liegt im umfangreichen und störungsanfälligen technischen Aufwand.The disadvantage of the circuit arrangements proposed in US Pat. No. 3,662,253 lies in the extensive and fault-prone technical outlay.

Die Aufgabe der Erfindung besteht daher darin, eine Anordnung bei einem Lastumschalter eines Stufenschalters zum unterbrechungslosen Um - schalten der Regelwicklung eines Transformators der eingangs genannten Art zu schaffen, welche die Nachteile der bekannten Anordnungen vermeidet und die Spannungs - und Strombelastung der Thyristoren beim Umschaltvorgang auf einem Minimum hält.The object of the invention is therefore to provide an arrangement in a load changeover switch of a tap changer for the uninterrupted switching of the control winding of a transformer of the type mentioned at the outset, which avoids the disadvantages of the known arrangements and the voltage and current loading of the thyristors during the switching process on one Minimum holds.

Die Aufgabe wird durch die Erfindung gelöst. Diese ist dadurch gekennzeichnet, daß der Entlastungskreis aus einem zweiten Umschalter und ei - nem dazu in Serie liegenden Thyristorkreis mit antiparallelgeschalteten Thyristoren besteht, und daß ein Überschaltwiderstand über einen Überbrückungsschalter mit der gemeinsamen Ableitung verbunden ist, und daß der eine Umschaltkontakt des zweiten Umschalters direkt und der andere Umschaltkontakt dieses zweiten Umschalters über den Überschaltwiderstand mit dem Wurzelanschluß des ersten Umschalters verbunden ist.The object is achieved by the invention. This is characterized in that the relief circuit consists of a second changeover switch and a thyristor circuit in series with antiparallel connected thyristors, and that a tripping resistor is connected to the common derivative via a bypass switch, and that the one changeover contact of the second changeover switch is direct and the other changeover contact of this second changeover switch is connected to the root connection of the first changeover switch via the transition resistor.

Durch diese Anordnung wird der Bauteilauf - wand, um ein lichtbogenfreies Schalten von einer Regelstufe zur anderen zu erreichen, relativ gering gehalten. Selbstverständlich wird damit auch ein Kontaktabbrand an den Dauerkontakten verhindert. In den Endstellungen erfolgt keine Belastung der Thyristoren, da sie durch den jeweiligen parallel angeordneten Dauerkontakt überbrückt sind. Eine Belastung der Thyristoren durch Kurzschlußströme ist ebenfalls vermieden.With this arrangement, the component expenditure in order to achieve an arc-free switching from one control stage to another is kept relatively low. Of course, this also prevents contact erosion on the permanent contacts. In the end positions, there is no load on the thyristors, since they are bridged by the respective permanent contact arranged in parallel. A load on the thyristors by short-circuit currents is also avoided.

Unter Zugrundelegung einer Überschaltzeit von 120 ms können die beim bekannten Lastumschalter verwendeten mechanischen Schaltelemente sowie die Überschaltwiderstände verwendet werden.On the basis of a switchover time of 120 ms, the mechanical switching elements used in the known diverter switch and the switchover resistances can be used.

Weiters ist vorteilhaft, daß nur eine Zündvorrichtung erforderlich ist, die im Laufe eines Umschaltvorganges zwei Mal betätigt wird.It is also advantageous that only one ignition device is required, which is actuated twice in the course of a switching process.

Nach einer Weiterbildung sind die beiden Dauerkontakte als ein weiterer Umschaltkontakt sind.According to a further development, the two permanent contacts are a further changeover contact.

Dadurch werden Schaltkontakte eingespart, und außerdem wird auf einfache Art die Ausführung als Lastwähler erreicht.This saves switching contacts, and in addition, the design as a load selector is achieved in a simple manner.

Die nähere Erläuterung der Erfindung erfolgt unter Zuhilfenahme von Zeichnungen, wobei Fig. 1 den erfindungsgemäßen Lastumschalter darstellt, und Fig. 2 und 3 die zugehörigen Ablaufdiagram - me sind.The invention is explained in more detail with the aid of drawings, in which FIG. 1 represents the diverter switch according to the invention, and FIGS. 2 and 3 are the associated flowcharts.

Fig. 1 zeigt eine Regelstufe 13 einer Regel - wicklung, deren Laststrom über eine niedere oder höhere Wicklungsanzapfung 11, 12 und über mindestens zwei Wählerkontakte 14, 15 und zwei Dauerkontakte 9, 10 einer gemeinsamen Ableitung 16 zuführbar ist. Die Umschaltung von der niederen auf die höhere Wicklungsanzapfung oder umgekehrt erfolgt über einen Umschalter 5, wobei der Laststrom kurzzeitig auf einen Entlastungskreis 17 übergeht, der zwischen dem Wurzelanschluß 6 des Umschalters 5 und der gemeinsamen Ableitung 16 angeordnet ist. Von den beiden Kontakten 7, 8 des Umschalters 5 ist jeweils einer an die Verbindung des Wählerkontakts 14, 15 mit dem Dauerkontakt 9, 10 gelegt.1 shows a control stage 13 of a control winding, the load current of which can be fed to a common derivative 16 via a lower or higher winding tapping 11, 12 and at least two selector contacts 14, 15 and two permanent contacts 9, 10. The changeover from the lower to the higher winding tapping or vice versa takes place via a changeover switch 5, the load current passing briefly to a relief circuit 17 which is arranged between the root connection 6 of the changeover switch 5 and the common derivative 16. One of each of the two contacts 7, 8 of the changeover switch 5 is connected to the connection of the selector contact 14, 15 to the permanent contact 9, 10.

Der Entlastungskreis 17 besteht aus einem Umschalter 18 und einem dazu in Serie liegenden Thyristorkreis 2 mit antiparallelgeschalteten Thyri - storen 2a, 2b. Ein Überschaltwiderstand 4 ist über einen Überbrückungsschalter 23 mit der gemeinsamen Ableitung 16 verbunden. Der eine Umschaltkontakt 20 des Umschalters 18 ist direkt, der andere Umschaltkontakt 21 über den Überschaltwiderstand 4 mit dem Wurzelanschluß 6 des Um - schalters 5 verbunden.The relief circuit 17 consists of a changeover switch 18 and a series thyristor circuit 2 with antiparallel connected thyristors 2a, 2b. A switching resistor 4 is connected to the common derivative 16 via a bypass switch 23. One changeover contact 20 of the changeover switch 18 is directly connected, the other changeover contact 21 is connected to the root connection 6 of the changeover switch 5 via the switching resistor 4.

Wie aus den Ablaufdiagrammen Fig. 2 und 3 ersichtlich, sind die Schaltzeiten für die Zündung der Thyristoren 2a, 2b asymmetrisch versetzt.2 and 3, the switching times for the ignition of the thyristors 2a, 2b are offset asymmetrically.

Diese Asymmetrie in beiden Schaltrichtungen, sowie die Endkontakt - Umschaltung des Umschalters 5 ist mechanisch herzustellen.This asymmetry in both switching directions, as well as the end contact changeover of the changeover switch 5 can be produced mechanically.

Im folgenden wird an Hand der Fig. 1 und 2 eine Umschaltung von der Stufenanzapfung 11 auf die Stufenanzapfung 12 der Regelstufe 13 einer Regelwicklung in Schritten beschrieben. Die links - seitigen Bezeichnungen in Fig. 2 entsprechen den Schaltern bzw. Thyristoren und Kontakten in Fig. 1. Außerdem bedeutet 11 _ 12 die Schaltrichtung von Anzapfung 11 auf 12. Von den zwei Feldern, wel - che sich auf den Thyristorkreis 2 beziehen, zeigt das erste Feld die Dauer der Zündimpulse, das zweite Feld die Dauer des Stromflusses durch die Thyristoren.1 and 2, a switchover from step tap 11 to step tap 12 of control stage 13 of a control winding is described in steps. The links - The designations on the side in FIG. 2 correspond to the switches or thyristors and contacts in FIG. 1. In addition, 11 _ 12 means the switching direction from tap 11 to 12. The first of the two fields which relate to the thyristor circuit 2 shows Field the duration of the ignition pulses, the second field the duration of the current flow through the thyristors.

Schrittstep

  • A Wählerkontakte 14, 15 und Dauerkontakt 9 geschlossen; Umschalter 5 verbindet Kontakt 7 über Wurzelanschluß 6 mit Entlastungskreis 17; Entlastungskreis 17 befindet sich im nichtleitenden Schaltzustand; Umschalter 18 verbindet Kontakt 20 mit Wurzelanschluß 19; Thyristorkreis 2 im nichtleitenden Schaltzustand; Überbrükkungsschalter 23 geschlossen; Laststrom fließt über Wicklungsanzapfung 11 der Regelstufe 13 der Regelwicklung, sowie über Wähler- 14 und Dauerkontakt 9 zur gemeinsamen Ableitung 16. Thyristorkreis 2 wird gezündet.A Selector contacts 14, 15 and permanent contact 9 closed; Switch 5 connects contact 7 via root connection 6 with relief circuit 17; Relief circuit 17 is in the non-conductive switching state; Changeover switch 18 connects contact 20 with root connection 19; Thyristor circuit 2 in the non-conductive switching state; Bridging switch 23 closed; Load current flows via winding tapping 11 of control stage 13 of the control winding, as well as via selector 14 and permanent contact 9 for common derivation 16. Thyristor circuit 2 is ignited.
  • B Dauerkontakt 9 öffnet, Thyristorkreis 2 übernimmt Laststrom.B Permanent contact 9 opens, thyristor circuit 2 takes over load current.
  • C Thyristorkreis 2 wird nicht mehr gezündet und führt Strom nur mehr bis zum näch - sten Nulldurchgang; danach fließt Laststrom über Überschaltwiderstand 4 und Überbrückungsschalter 23.C Thyristor circuit 2 is no longer ignited and only carries current until the next zero crossing; after that, load current flows through contact resistance 4 and bypass switch 23.
  • D Umschalter 18 öffnet, Dauerkontakt 10 schließt; Laststrom, vermindert um den Ausgleichsstrom, fließt über Wicklungsanzapfung 12, Wählerkontakt 15 und Dauerkontakt 10 zur gemeinsamen Ablei - tung 16; Ausgleichsstrom fließt über Überschaltwiderstand 4 und Kontakt 23.D switch 18 opens, permanent contact 10 closes; Load current, reduced by the compensating current, flows via winding tapping 12, selector contact 15 and permanent contact 10 to the common lead 16; Compensating current flows through contact resistance 4 and contact 23.
  • E Umschalter 18 verbindet Wurzelanschluß 19 mit Kontakt 21, Thyristorkreis 2 wird gezündet.E changeover switch 18 connects root connection 19 with contact 21, thyristor circuit 2 is ignited.
  • F Überbrückungsschalter 23 öffnet; Ausgleichsstrom fließt über Thyristorkreis 2.F bypass switch 23 opens; Compensating current flows through thyristor circuit 2.
  • G Thyristorkreis 2 wird nicht mehr gezündet und führt den Ausgleichsstrom nur mehr bis zum nächsten Nulldurchgang; danach fließt Laststrom über Wicklungsanzapfung 12, Wählerkontakt 15 und Dauerkontakt 10 zur gemeinsamen Ableitung 16.G Thyristor circuit 2 is no longer ignited and only leads the compensating current until the next zero crossing; then load current flows via winding tapping 12, selector contact 15 and permanent contact 10 to the common derivation 16.
  • H Umschalter 5 schaltet Wurzelanschluß 6 von Kontakt 7 auf Kontakt 8.
    I Umschalter 18 schaltet von Kontakt 21 auf Kontakt 20; Überbrückungsschalter 23 schließt; damit ist der Entlastungskreis für die nächste Stufenumschaltung bereit.    H Switch 5 switches root connection 6 from contact 7 to contact 8.
    I switch 18 switches from contact 21 to contact 20; Bypass switch 23 closes; the relief circuit is now ready for the next level changeover.

Für den Entlastungskreis nach Fig. 1 gelten nachfolgende Zusammenhänge. Strom - Belastungsdauer des Thyristorkreises 2: tL ... 15 + 20 ms

  • Spannungsbelastung des Thyristorkreises 2: UTH = IL x Rü
  • Belastung des Thyristorkreises 2 durch Ausgleichsstrom:
    Figure imgb0001
  • Ausgleichsstrom - Belastungsdauer: tA ... 5 + 15 ms
The following relationships apply to the relief circuit according to FIG. 1. Current - load duration of the thyristor circuit 2: t L ... 15 + 20 ms
  • Voltage load of the thyristor circuit 2: U TH = I L x Rü
  • Load of thyristor circuit 2 by compensating current:
    Figure imgb0001
  • Balance current - load duration: t A ... 5 + 15 ms

Hierbei sind:

  • tL Strom - Belastungsdauer
  • IL Laststrom
  • IA Ausgleichsstrom
  • UTH Spannung am Thyristor
  • EST Stufenspannung
  • Rü Überschaltwiderstand
  • tA Ausgleichsstrom - Belastungsdauer
Here are:
  • t L current - load duration
  • I L load current
  • I A equalizing current
  • U TH voltage at the thyristor
  • E ST step voltage
  • Rü overvoltage resistance
  • t A equalizing current - load duration

An Hand der Fig. 1 und 3 wird eine andere Vari - ante der Umschaltung von der Stufenanzapfung 11 auf die Stufenanzapfung 12 der Regelstufe 13 der Regelwicklung beschrieben.Another variant of the changeover from the tap tapping 11 to the tap tap 12 of the control stage 13 of the control winding is described with reference to FIGS. 1 and 3.

Die Schritte A bis C sind äquivalent mit der vorigen Beschreibung des Umschaltvorganges. Die weiteren Schritte sind nachfolgend angeführt.

  • D Umschalter 18 schaltet Wurzelanschluß 19 von Kontakt 20 auf Kontakt 21. Thyristor - kreis 2 wird gezündet.
  • E Überbrückungsschalter 23 öffnet; Thyristorkreis 2 übernimmt den Laststrom.
  • F Dauerkontakt 10 schließt; Laststrom, vermindert um den Ausgleichsstrom, fließt über Stufenanzapfung 12, Wählerkontakt 15 und Dauerkontakt 10 zur gemeinsamen Ableitung 16; Thyristorkreis 2 führt den Ausgleichsstrom.
  • G Thyristorkreis 2 wird nicht mehr gezündet und führt den Ausgleichsstrom nur mehr bis zum nächsten Nulldurchgang.
  • H Umschalter 5 schaltet Wurzelanschluß 6 von Kontakt 7 auf Kontakt 8. I Umschalter 18 schaltet von Kontakt 21 auf Kontakt 20; Überbrückungsschalter 23 schließt; damit ist der Entlastungskreis für die nächste Stufenumschaltung bereit.
Steps A to C are equivalent to the previous description of the switching process. The next steps are listed below.
  • D Changeover switch 18 switches root connection 19 from contact 20 to contact 21. Thyristor circuit 2 is ignited.
  • E bypass switch 23 opens; Thyristor circuit 2 takes over the load current.
  • F permanent contact 10 closes; Load current, reduced by the compensating current, flows via tap tapping 12, selector contact 15 and permanent contact 10 to the common derivative 16; Thyristor circuit 2 carries the equalizing current.
  • G Thyristor circuit 2 is no longer ignited and only leads the compensating current to the next zero crossing.
  • H switch 5 switches root connection 6 from contact 7 to contact 8. I switch 18 switches from contact 21 to contact 20; Bypass switch 23 closes; the relief circuit is now ready for the next level changeover.

Claims (2)

1. An arrangement in the case of a load change - over switch in a tap switch for switching over the control winding of a transformer without interruption of operation, the load current being supplied via a lower or higher winding tap (11, 12) to a control stage (13) of a control winding and via a connection between at least two selector contacts (14, 15) and two permanent contacts (9, 10) with a common charge elimi - nator (16), and the switching-over from the lower to the higher winding tap (11, 12) or vice versa being made via a first change-over switch (5) by briefly transferring the load cur - rent to a discharge circuit (17) disposed be - tween the common charge eliminator (16) and the root connection (6) of the first change - over switch (5), and a respective one of the two contacts (7, 8) of the first change-over switch (5) being connected to a connection between a selector contact (14, 15) and a permanent contact (9, 10), characterised in that the discharge circuit (17) comprises a second change-over switch (18) and a thyristor circuit (2) in series therewith and made up of antiparallel connected thyristors (2a, 2b), and a transition resistor (4) is connected to the common charge eliminator (16) via a transition resistor (23), and one contact (20) of the sec - ond change - over switch (18) is directly connected to the root connection (6) of the first change-over switch (5) whereas the other contact (21) of the second change-over switch (18) is connected thereto via the transition resistor (4).
2. An arrangement according to claim 1, charac - terised in that the two permanent contacts (9, 10) are in the form of an additional change - over contact.
EP88905150A 1987-06-25 1988-06-14 Thyristor on-load change-over switch Expired - Lifetime EP0375687B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT0160187A AT400496B (en) 1987-06-25 1987-06-25 THYRISTOR LOAD SWITCH
AT1601/87 1987-06-25
PCT/AT1988/000045 WO1988010502A1 (en) 1987-06-25 1988-06-14 Thyristor on-load change-over switch

Publications (3)

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EP0375687A1 EP0375687A1 (en) 1990-07-04
EP0375687B1 true EP0375687B1 (en) 1993-05-12
EP0375687B2 EP0375687B2 (en) 1997-04-02

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US (1) US5006784A (en)
EP (1) EP0375687B2 (en)
JP (1) JP2662434B2 (en)
AT (2) AT400496B (en)
BG (1) BG50510A3 (en)
DE (1) DE3881052D1 (en)
HU (1) HU203425B (en)
SU (1) SU1739862A3 (en)
WO (1) WO1988010502A1 (en)

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Also Published As

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ATE89433T1 (en) 1993-05-15
WO1988010502A1 (en) 1988-12-29
EP0375687A1 (en) 1990-07-04
DE3881052D1 (en) 1993-06-17
BG50510A3 (en) 1992-08-14
AT400496B (en) 1996-01-25
HU203425B (en) 1991-07-29
JP2662434B2 (en) 1997-10-15
ATA160187A (en) 1991-12-15
JPH03500224A (en) 1991-01-17
SU1739862A3 (en) 1992-06-07
HUT52270A (en) 1990-06-28
EP0375687B2 (en) 1997-04-02
US5006784A (en) 1991-04-09

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