DE1272418B - Circuit arrangement for electrical switches - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

HOIh

German class: 21c-35/07

Number: 1272418

File number: P 12 72 418.4-34 (K 58538)

Filing date: February 24, 1966

Opening day: July 11, 1968

The invention relates to a circuit arrangement for limiting the voltage on electrical switches with a device for generating a switching arc, in particular for current limiting switches in high-voltage, preferably direct-current systems, in which one is parallel to the switch expedient current-dependent resistor, a capacitor and a spark gap are provided.

It is known that the elimination of direct current high voltage circuits Significant difficulties with it, since the current due to lack of the natural zero crossing by special measures must be brought to the value zero. With the size of the DC circuit to be switched off located inductors increase the difficulty, since the stored in the inductors magnetic energy must be consumed while switching off.

The development of switching devices for direct current high-voltage systems is about so overcoming the difficulties described went two different ways. In one case it has attempts are made to use the circuit arrangement mentioned in the introduction using appropriately sized Capacitors or capacitors to a system that works as a resonant circuit when it is switched off create whose current goes through zero, so that you can also use an AC switch for the DC circuit can use. With this arrangement, which is described in German patent application B 7741 VIIIb / 21c is described, the capacitor is arranged in parallel with the switch, and is parallel to it the resistor in series with a switch for switching off the residual direct current. It will recommended to facilitate the current transfer to the parallel path to the resistor and / or the A controllable switching device to be connected upstream of the capacitor.

Another known circuit arrangement of this type provides a series connection in parallel with the capacitor consisting of an ohmic resistor and a spark gap with an arc extinguishing device, due to the dangerous overvoltages occurring at the capacitor to an adjustable permissible Value can be reduced.

However, these circuit arrangements have the disadvantage that at high currents in the to be switched off Circuit correspondingly large capacitors are required, so that the effort for this is very big. In every practical case the "residual direct current" will still be so great that its interruption similar difficulties be-circuit arrangement for electrical switches

Applicant:

Dr.-Ing. Dieter Kind,

3300 Braunschweig, Pockelsstr. 4th

Named as inventor:

Dr.-Ing. Dieter Kind,

Dr.-Ing. Erwin Marx, 3300 Braunschweig;

Dr.-Ing. Jürgen Salge, 3321 Salzgitter-Osterlinde

rides like the interruption of the main stream. These known circuit arrangements are of practical importance not obtained.

In the other way, switches have been developed that generate a high arc voltage as quickly as possible generate and maintain, so that the current is thereby forced to zero, the duration of the Switching off depends on the level of the arc voltage, the level of the current to be switched off and the inductances in the circuit to be switched off. With these switches, according to recent proposals as a liquid switch with narrow gaps for the arc and at right angles to the longitudinal axis of the arc are executed over the entire length of the effective extinguishing flow, this inevitably results an extinguishing peak of the arc voltage, which is essentially determined by the inductance of the circuit and the change in the current over time, the tip of the hole being higher, depending the action of the extinguishing agent on the arc is more intense. When the rapid power interruption required high extinguishing agent flow leads to a high extinguishing peak, this causes the Use of switches with a high switching capacity, but without this switching capacity being fully utilized can be.

The invention is based on the object of creating a circuit arrangement through which both a very fast limitation of the current to be switched off as well as a current zero without high Extinguishing tip is enabled.

To solve this problem, the invention is based on the one mentioned in the introduction, but a different one Purpose-serving arrangement and is characterized by the fact that to limit the voltage on Switch the parallel circuit from a series connection of the resistor, the capacitor and the spark gap consists.

809 569/435

With this new arrangement, the response voltage of the spark gap is adjusted accordingly when the arc voltage exceeds the permissible value, the current on the The parallel path commutates and thus the switch current to zero and its voltage to that on the parallel circuit brought certain tension by its data. Since only a stream of small size on the Parallel circuit is to commutate, resistor and capacitor are compared to the well-known Arrangements dimensioned only very small.

Because the resistor is connected in series with the capacitor, there can be no residual direct current in the parallel path to the switch are maintained and thus also the otherwise necessary switch in the parallel path omitted.

The circuit arrangement according to the invention thus differs significantly from a known one Device for arc suppression on switching contacts, in particular on high-voltage switches, in which a quenching spark gap located in an oscillating circuit is connected in parallel to the switching contacts is. The quenching spark gap should respond in the event of overvoltages in the circuit to be switched off and thereby initiate the oscillation process in the oscillating circuit, which then leads to destruction of the magnetic energy in the circuit to be switched off and in this way the occurrence of a Prevents arcing at the high-voltage switch. In the circuit arrangement according to the invention but in contrast to this, the occurrence of an arc with a very high arc voltage is necessary, to commutate the current on the parallel path. The switch voltage is thereby through the series circuit of capacitor, resistor and spark gap lying parallel to the switch limits a permissible value.

According to a further feature of the invention it is provided that the response voltage of the spark gap adjustable to the maximum permissible voltage on the switching device and the resistance is dimensioned in such a way that that the voltage drop occurring on it when the spark gap responds, i.e. during commutation of the current on the parallel circuit remains below the maximum permissible voltage at the switch.

The capacitance of the capacitor is appropriate depending on the size of the one in series lying resistance of the parallel circuit to be dimensioned so that when the through the parallel circuit is interrupted residual current flowing, the voltage on this circuit is below the maximum permissible voltage remains at the counter.

In other words, the voltage k _s occurring at the switching device must be determined by the equation

= i-R (i) + -

60

remain below the maximum permissible value, with i in the equation denoting the current in the parallel circuit after the commutation has taken place.

Since the resistance has the highest voltage at the moment of commutation of the current from the If the switch is intended for the parallel circuit, the size of the capacitance has no influence on its dimensioning. On the other hand, when dimensioning the capacitor, the beneficial effect of the resistor must be taken into account.

In the drawing, the new arrangement is shown together in schematic form as a circuit diagram with an associated diagram showing the course of the currents and voltages, for example according to the above equation.

The switch, which is arranged in the main current path H , is denoted by S in the circuit diagram. A capacitance C, a resistor R and the spark gap F, the response voltage of which is adjustable, are arranged in series parallel to the switch.

The associated diagram shows the respective current and voltage curve from the moment the spark gap F responds at time t ₀ , the individual curves being identified by corresponding indices of the elements shown in the circuit or information from the above equation.

The new circuit arrangement is not only for DC switches, especially high-speed switches, suitable, but can also be used for quick switches, i.e. H. Current limit switches in AC circuits Find application. Although also the preferred use in DC high voltage circuits occurs, then with rapid shutdowns in AC circuits, that is, shutdowns in the first half-wave with simultaneous limitation of the short-circuit current to similar conditions as in DC circuits.

Claims (3)

Patent claims: 1. Circuit arrangement for limiting the voltage on electrical switches with a device for generating a switching arc, especially for current limiting switches in high-voltage, preferably direct current systems, in which one expediently parallel to the switch current-dependent resistor, a capacitor and a spark gap are provided, thereby characterized in that the parallel circuit consists of a series connection of the resistor, the capacitor and the spark gap. 2. Arrangement according to claim 1, characterized in that the response voltage of the The spark gap can be set to the maximum permissible voltage on the switching device, and so is the resistance is dimensioned so that the voltage drop occurring on it when the spark gap responds, d. H. when commutating the current to the parallel circuit below the maximum permissible Voltage remains on the switch. 3. Arrangement according to claim 1 or 2, characterized in that the capacity of the Capacitor is dimensioned depending on the size of the resistor so that in the event of an interruption of the residual current flowing through the parallel circuit, the voltage on the parallel circuit is below the maximum permissible voltage on the switch remains. Considered publications: German Patent Specifications No. 521636, 1151636. 1 sheet of drawings 809 569/435 7. 68 © Bundesdruckerei Berlin