DE2062193C3 - Device for the compulsory quenching of a thyristor - Google Patents

Description

The invention relates to a device for the forced deletion of a main thyristor, which is connected in series a load is connected to a DC voltage source, an erase voltage pulse being shunted to one of the main thyristor switched secondary winding of a transformer inductively when igniting one with the primary winding of the transformer in series-connected thyristor is generated and this is a Capacitor is provided. Such a device is known (DT-OS 14 38 500).

In the known device, as in the basic circuit for the thyratron extinguishing the DT-PS 6 82 532 for the forced extinction of a thyristor with the help of an extinguishing capacitor an extinguishing voltage pulse generated in the shunt of the thyristor to be extinguished and connected to this. Deletion circuits according to this basic circuit with a quenching or commutation capacitor generally used in converters with thyristors. Essential in the various applications the capacitor extinguishing circuit is always that at the point in time in which a thyristor is extinguished should, the assigned quenching capacitor must be charged ready to be erased. The readiness to delete the Quenching capacitor is therefore during operation and in many cases even before commissioning Constantly monitor the thyristor system (DT-AS 11 49 107). For this are electrical monitoring and Signaling equipment required, whose signals are transmitted to the control system of the plant and for an operationally safe control can be evaluated (DT-AS 14 88 968). For systems with many thyristors the effort for this monitoring and for the control can sometimes be quite large. With plants the power electronics also speaks the capacity size of the extinguishing condensers used ;; ators play a role, because it is the required capacitance of these capacitors in relation to an equally large charging voltage proportional to the product of the operating current and the time the thyristors become free (VDE technical reports No. 23, 1964, p. 240).

If in a power electronic system (AEG-Mitteilungen 54 (1964) p. 105) the thyristors in Pulse operation with pulse frequencies in the range from 400 to a few thousand Hertz, then arise in the quenching capacitors, and not only in these, large losses. In the case of thyristors, the losses can occur Suitable acoustic irradiation, in the case of throttles, can be kept to a minimum by means of an eddy current-free core material. Quenching capacitors can only be used if they have a suitable construction and suitable material and are unwieldy Oil sizes can be made low-loss.

In power electronics, the use of the capacitor extinguishing process is predominant. Used is also an erase method with a circuit (US-PS 33 28 596) in which the thyristor with a Resonant circuit is connected, in which a capacitor works like a quenching capacitor and with the help of a Choke is reloaded, and in which the thyristor is extinguished when the current swings back.

As is well known, a thyristor can also be extinguished by an inductively generated voltage by the Quenching voltage from a capacitor or from a generator by means of a connected in series with the thyristor Transformer is impressed into the circuit (VDE-Fachberichte No. 23, 1964, p. 240, Fig 4 g, h), (FR-PS 15 23 909).

It is also an arrangement for forced commutation of a thyristor inverter with free-wheeling diodes known (DT-OS 15 63 232), in which the quenching voltage pulses for the thyristors via quenching transformers, which are in the freewheeling circuits of the thyristors are generated, so that the erase voltage pulses can be induced into the inverter's freewheeling circuits. This arrangement has opposite Quenching circuits with a quenching capacitor have the advantage that when the commutation is initiated voltage on the load is not increased by the voltage of a commutation capacitor and that the voltage acting in the reverse direction on the freewheeling diodes does not increase by the same amount will. Furthermore, in the known arrangement of

The quenching circuit is galvanically separated from the working circuit by the quenching transformer, which is a high-voltage inverter matters. However, there are in the primary circuits of the quenching transformers four auxiliary thyristors required, of which two thyristors themselves are forcibly extinguished have to.

The DTOS 14 38 500 mentioned at the beginning is an inverter with two thyristors in a push-pull circuit known, in which the current-carrying thyristor is extinguished when the current-free thyristor is triggered becomes (phase sequence deletion). With every thyristor the erase voltage pulse is applied to a tertiary winding of the ignition transformer, which is connected in series with a capacitor to shunt the Thyristor forms. Here the capacitor does not have the function of a quenching capacitor. Because of the push-pull circuit the two thyristors cannot be ignited and extinguished independently of each other. The inverter voltage can therefore not be changed by controlling the inverter. Furthermore, only short-term extinguishing voltage pulses can be generated with the ignition transformers and therefore only Thyristors with a short idle time can be deleted.

The invention is based on the object of creating a device for the forced extinction of a thyristor , in which a quenching transformer is connected in the shunt of the thyristor to be quenched, and with which the relevant thyristor as well as thyristors with an even greater free time and greater Rated current than the aforementioned known inverter with a small number of auxiliary thyristors deleted at any point in time.

The solution to this problem is a facility of the type mentioned according to the invention in that using a saturable transformer the primary winding of the transformer over the ignited one to generate the extinguishing voltage pulse Quenching thyristor and is connected via the capacitor to the DC voltage source that the Secondary winding of the transformer generated release voltage impulses by an ignited shortly after the quenching thyristor and lying in series with the secondary winding Auxiliary thyristor is connected to the main thyristor to be deleted, that the capacitor is so he measure is that the current through the capacitor just before or when the transformer begins to saturate is reduced below the holding current strength of the quenching thyristor and that the reverse magnetization current of the transformer secondary winding less than the holding current of the auxiliary thyristor is.

In order to keep the transformer ready to be extinguished again after the main thyristor is re-ignited, it is appropriate an embodiment of the invention for magnetizing the transformer back when reigniting the Main thyristor a diode connecting the primary winding and the anode of the main thyristor is provided.

According to a further embodiment of the invention, the transformer is independent of magnetizing back from the re-ignition of the main thyristor, another auxiliary thyristor is provided through which the primary winding connected in parallel to the charged capacitor at any point in time after the extinguishing process will.

For the use of only one auxiliary thyristor, in a still further embodiment of the invention there is a cathode of the quenching thyristor with the anode of the diode and with the anode of the auxiliary thyristor in the shunt current path of the main thyristor connected.

The device according to the invention enables the individual deletion as well as the total deletion of several thyristors or thyristor groups that cannot be deleted at the same time, ζ. Β with a converter. Therefor this device can be modified so that the reverse magnetization of the quenching transformer generated voltage pulse is used to quench thyristors.

On the basis of FIG. 1 to 3 are exemplary embodiments below the invention described with Löschaiuingen for individual deletion of a thyristor. At 4 shows an embodiment of the invention explained for an inverter.

The Löschsehalningen according to the F i g. 1 to 3 are each assigned to a main thyristor 1, which is connected in series with a direct voltage source G and a load L in a simple direct current circuit are connected in series and that a series circuit consisting of a quenching thyristor 2, a capacitor K and the primary winding 41 of the transformer is connected directly to the DC voltage source C. With respect to the DC voltage source G, the thyristors 2 and 3 have the same polarity as the thyristor! The quenching transformer 4 is saturable and has a transformer core with a rectangular magnetization characteristic. Induction swing ABs and cross section q of the transformer core are selected to be so large that the quenching transformer has a voltage-time area sufficient to quench the main thyristor 1. If, under this condition, the transformer is magnetized into the remanence position, which is achieved by a magnetizing current flowing in the forward direction of the auxiliary thyristor 3 or by a magnetizing current flowing in the reverse direction of the quenching thyristor 2, then with the ignition of the quenching thyristor 2 a via the primary winding 41 in the Capacitor K switched on flowing current pulse, the core of the transformer 4 being unmagnctized and a voltage pulse with extinction polarity being generated on the secondary winding 42. By igniting the auxiliary thyristor 3 shortly after igniting the extinguishing thyristor 2 and the occurrence of the extinguishing pulse, the extinguishing voltage pulse is switched to the main thyristor 1 in the reverse direction. This is then erased because, as required, the duration of the erase voltage pulse is longer than the time the main thyristor becomes free. After the erase voltage pulse has arisen, the quenching transformer 4 is briefly (some) loaded by the clearing current of the main thyristor 1. This current flows in the reverse direction of the thyristor 1 and in the shunt of the same in the forward direction of the auxiliary thyristor 3 Capacitor K) roughly the quenching voltage, which drops in the shape of a corner, and depends on the resistance of the load L. This current pulse flows from the secondary winding 42 via the load L and on via one between the negative pole of the

DC voltage source C and the cathode of the quenching thyristor 2 connected diode 5 and the auxiliary thyristor 3 in the secondary winding 42 back. The capacitance of the capacitor K is to be dimensioned so that it is charged to the voltage of the equilibrium voltage source G after the magnetization has been reversed and the transformer core is saturated, so that the charging current disappears and the quenching thyristor 2 extinguishes itself. Furthermore, the magnetization current of the quenching transformer 4 must be kept smaller than the holding current of the auxiliary thyristor 3 so that after the quenching pulse has ended, the quenching transformer 4 cannot be magnetized back via the auxiliary thyristor 3 and the load L under the influence of the voltage of the capacitor K and the DC voltage source , since the auxiliary thyristor 3 then deletes itself. The re-magnetization only takes place when the main thyristor 1 is re-ignited. The capacitor K is discharged via the primary winding 41 of the transformer 4, the main thyristor 1 and the load L. The discharge current is limited to the magnetizing current of the primary winding 41, which means that it cannot act as a dangerous “inrush current” on the ignited main thyristor 1. The erasing process is ended after the erasing voltage pulse has ended. As is known, the deleted main thyristor 1 can then be blocked again in the forward direction. When the deletion method described is carried out, the extinguished main thyristor 1 can also be ignited again immediately and then switched at a high switching frequency. The auxiliary thyristor 3, which is then approximately still conductive, is forcibly extinguished by the reverse magnetization voltage of the secondary winding 42.

Soft magnetic materials with a high specific electrical resistance come into consideration as core material for the transformer core in order to keep core losses small. Solid cores made of ferrite as well as thin strip or sheet metal are suitable as core material. Foil tape cores made of high-alloy materials. The latter have the advantage over the former that they have a two to three-fold induction stroke ABs. z. B about 3OkG. exhibit. The transformer core consists of a number of toroidal cores stacked on top of one another, which together result in the required core cross-section. The transformer windings 41 and 42 can be designed in such a way that one conductor each is passed through the toroidal core stack (single-conductor transformer) or that one conductor each optionally also passes two or more times in the manner of a winding. The conductors can have small cross-sections.

In one according to FIG. 1 executed quenching circuit arrangement, the primary circuit of the quenching transformer 4 with the elements quenching thyristor 2 and capacitor K is separated from the secondary circuit. Here, the quenching thyristor 2, as can be seen, a diode 6, through which the discharge current of the capacitor K flows, connected in antiparallel. The diode 6 is connected in series with the above-mentioned diode 5 in the same direction and is biased together with this by the voltage of the DC voltage source G in the reverse direction.

In contrast to the circuit arrangement according to FIG. 1 falls in the case of one according to FIG. 2 executed Quenching circuitry removes the diode 6. In this circuit arrangement, a further auxiliary thyristor 6 ' provided, which is ignited after extinguishing the Hauptthyri stors I to reverse the magnetization of the To enable transformer 4 regardless of the ignition timing of the main thyristor 1.

In contrast, one according to FIG. 3 executed quenching circuit arrangement of the quenching thyristor 2 with in the shunt of the main thyristor 1 and is therefore connected in series with the auxiliary thyristor 3 and with the secondary winding 42 of the quenching transformer. At the cathode of the quenching thyristor 2, the primary circuit branches off from the secondary circuit of the transformer 4. As in the circuit arrangement according to FIG. 1, a diode 6 is connected in anti-parallel to the quenching thyristor 2 here. In the circuit arrangement according to FIG. 3, the auxiliary thyristor 3 is also ignited shortly after the quenching thyristor. The clearing current of the main thyristor 1 then also flows through the quenching thyristor 2. In this circuit arrangement, with the aid of an inductance 7 and a resistor 8, which are shown in FIG. 3 are indicated by dashed lines, the capacitor K can be charged to a higher voltage than the voltage aer Gleichjo voltage source C, so that after termination of the erase voltage pulse, the erasure of the thyristor 2 is supported by a counter voltage. In this case, the transformer 4 can also be remagnetized immediately by the discharge current of the capacitor K via the auxiliary thyristor 3, provided that its holding current is not greater than half the magnetization current of the transformer 4 with a turns ratio of 1.

The extinguishing circuit arrangements according to FIGS. 1 and 2 can also be part of the voltage of the DC voltage source or operated on a separate DC voltage source. Here is the Primary circuit of the quenching transformer 4 to a partial voltage of the DC voltage source or to the separate DC voltage source connected. When operating at a partial voltage, a transformer core given voltage-time area a correspondingly longer extinguishing pulse than during operation can be generated across the entire voltage, or the transformer core can be used for a given pulse duration be reduced accordingly.

When operating on a separate DC voltage source, the primary circuit is from the DC operating circuit galvanically separated, what for the use of the extinguishing circuit arrangement described is advantageous in high-voltage thyristor circuits.

From the foregoing it is clear that the inventor

tion with different variants of Löschschal processing arrangements can be carried out. Possible use

possibilities of the procedure are expected at thyri

storized DC circuits and inverters tern given. The circuit arrangement according to FIG. 4th

a single-phase inverter in push-pull circuit

with two thyristors canceled in phase sequence, yield

from the circuit arrangement of FIG. 1 thereby

that the auxiliary thyristor 3 as a thyristor of the opposite phase

and the clearing thyristor 2 for clearing the main thyristor stors 1 can be provided. The quenching transformer <is assigned to the two thyristors 1, 3 together

and is designed on the primary side in a midpoint connection

likewise a transformer Ü for those with the push-pull

circuit generated alternating voltage, the output side

tig is connected to a load L. Another extinguishing thyristor 2 'is used to extinguish the auxiliary thyristor:

and instead of the diode 6 according to FIG. 1 to the back magnet

tization of the quenching transformer required.

1 sheet of drawings

Claims (4)

Patent claims: 1. Device for the forced quenching of a main thyristor which is connected in series to a load on a DC voltage source, a quenching voltage pulse being generated inductively on a secondary winding of a transformer connected in the shunt of the main thyristor when a quenching thyristor connected in series with the primary winding of the transformer is triggered and for this purpose a capacitor is provided, characterized in that the primary winding (41) of the transformer (4) via the ignited extinguishing thyristor (2) and via the capacitor (K) to the DC voltage source using a saturable transformer (4) to generate the extinguishing voltage pulse (G) is connected so that the extinguishing voltage pulse generated on the secondary winding (42) of the transformer (4) is applied to the main thyristor (3) to be extinguished by an auxiliary thyristor (3) which is ignited shortly after the extinguishing thyristor (2) and is in series with the secondary winding (42). 1) is connected that the capacitor (K) derar t is dimensioned so that the current through the capacitor (K) is reduced shortly before or at the beginning of saturation of the transformer (4) below the holding current strength of the quenching thyristor (2), and that the reverse magnetization current of the transformer secondary winding (42) is less than the holding current strength of the auxiliary thyristor (3) is dimensioned. 2. Device according to claim 1, characterized in that for remagnetizing the transformer (4) when the main thyristor (1) is re-ignited, the primary winding (41) and the anode of the Main thyristor (1) connecting diode (6) is provided (Fig. 1). 3. Device according to claim 2, characterized in that a further auxiliary thyristor (6 ') is provided for remagnetizing the transformer (4) regardless of the re-ignition of the main thyristor (1), via which the primary winding (41) at any point in time the charged capacitor (K) is connected in parallel to the deletion process (FIG. 2). 4. Device according to claim 2, characterized in that the cathode of the quenching thyristor (2) with the anode of the diode (6) and with the anode of the auxiliary thyristor (3) in the shunt path of the main thyristor (1) is connected (Fig. 3).