DE1083407B - Arrangement for overcurrent and short circuit interruption in rectifier systems - Google Patents

Description

GERMAN

In rectifier systems, especially those equipped with semiconductor valves, the Overcurrent and short circuit protection pose a difficult problem. Because of the very low thermal capacity the rectifier elements must have a power interruption in a few milliseconds in the event of a short circuit be forced to avoid destruction of the semiconductor crystals. Such extreme Short switch-off times can hardly be achieved with conventional circuit breakers.

There are switches with special type of drive systems known which switching times of a Have milliseconds and less. However, such switches can practically only be de-energized switch, since the achievement of the short proper times a contact system with very small distances and requires corresponding contact distances

It has already been proposed to have a choke coil in the main circuit with highly saturated Iron core at zero current, d. H. at the transition of the current from the operational current direction to the reverse current direction, a so-called weak current To force a break and to open the switch within this. Such an arrangement however, it has the disadvantage that it is only used in backflows, i. H. in the event of internal short circuits in the rectifier systems it is applicable that a shutdown of external short circuits is not possible.

Another proposed arrangement, in which parallel to a Sehalter with extremely short Proper time a fuse of low rated current is arranged, which the actual current interruption is left after opening the switch, is fraught with disadvantages. In particular means the required replacement of the fuse after each switch trigger for operation a considerable difficulty.

When feeding alternating current consumers from an alternating current network via two antiparallel Switched valves (or valve groups), in which the positive and negative healing sources of the AC current to flow through one of the two valves, it is known to arrange switches with the valves are in series and now for the purpose of switching the AC consumer on and off can be switched during the blocking time of the assigned valve.

Apart from the significantly different purpose of such an arrangement, in known designs the same switch is provided by a synchronous motor according to given control commands in synchronism to be operated for mains voltage.

The use of switch actuations synchronized in this way is very complex.

Arrangement for overcurrent

and short-circuit interruption

in rectifier systems

Applicant:

Brown, Boveri & Cie. Aktiengesellschaft, Mannheim-Käfertal, Boveristr. 22nd

Karl-Werner Kanngiesser, Mannheim,
has been named as the inventor

In addition, it is not ensured with this arrangement that the switches only in the de-energized state switch. This is namely not the case when the valve action of the valves used as a result a flashback or a valve breakdown in semiconductor valves. It has already been suggested been used to switch off short circuits in DC circuits via rectifier valves be fed in a bridge circuit when an overcurrent occurs in one direction depending on the overcurrent, a switching element located in the path of the other current direction is closed open so that a current flow in the other direction is prevented.

In this arrangement there is a special synchronous motor for actuating the switching element not necessary, but here too there is the last-mentioned disadvantage of the aforementioned arrangement, especially when the rectifier arrangement consists of semiconductor valves. If the Valves of one current path have become defective due to a valve breakdown, so can one the overcurrent caused by this does not open the relevant switching element without current, but must the Interrupt short-circuit current. Since this switching element is not suitable for such a power shutdown, it would also be If the valve is already defective, the switching element will also be destroyed.

In contrast, the invention provides an arrangement for interrupting overcurrent and short-circuit currents in rectifier systems by extremely fast switches assigned to the individual valve circuits, the are opened during the blocking phase of the relevant valve section with the indicator that the opening

009 530/422

each of these switches by a coincidence element is effected, one input variable of which the information about an existing overcurrent and a or several other input variables the information about the currentlessness of the assigned valve section with the command to open the switch when the input variables coincide.

Such an arrangement works in such a way that, in the event of an overcurrent, only the switches of those Immediately open valve sections that are not energized, i.e. are in the blocking phase. The switches who at the moment; the start of the short circuit, the current-carrying valve sections remain closed as long as until the current in them has decayed to zero at the end of the current-carrying phase. The shutdown process runs similar to the grid closure of a multi-anode gas discharge vessel.

The opening of one of the switches in series with the valve sections is energized by the Arrangement of the invention excluded.

Fig. 1 shows the basic arrangement of switches 1 and valve sections 2 using the example of a Rectifier system in three-phase bridge circuit, which is fed from a three-phase current source 3.

Fig. 2 shows as an embodiment an arrangement according to the invention for a valve section with the associated switch of such a rectifier system. By one in the main circuit of the rectifier system lying direct current converter 4 a voltage proportional to the direct current is generated, after rectification by the rectifier 5 as a current-proportional DC voltage on Load resistance 6 is. Instead, the voltage, which is proportional to the direct current, can also be used AC converters can be obtained in the AC feed lines of the rectifier system. In row with this voltage there is a DC voltage of opposite polarity that can be set at the potentiometer 7, with which the response value of the device can be set. Through the valve 8 is a Current in the opposite direction to the burden voltage prevented. The resulting voltage is the switching element 9 of the coincidence element supplied.

In the example, the coincidence element consists of two switching elements 9 and 11, each with an opening contact. In the closed state, these contacts bridge the triggering device connected to a current source 14, 15 16 of the switch 1 assigned to the relevant valve path (FIG. 1). Resistance 10 serves to justify the current flowing through these contacts.

The switching element 11 is controlled by an alternating voltage tapped at the resistor 12, which is synchronous with the AC supply voltage of the rectifier system and has such a phase position, that the switching element 11 responds during the blocking phase of the associated valve path, wherein the valve 13 only allows one half-wave to be effective. With the adjustable on potentiometer 17 DC voltage, the opening duration of the switching element 11 can be set.

At the moment when both switching elements respond at the same time, i. H. so if during the Blocking phase, an overcurrent is present, the switch tripping device 16 receives voltage, so that the The associated switch is opened.

The switching elements 9 and 11 of the coincidence element are advantageously not, as indicated in the drawing is, contact relays are used, but electronic switching elements that give the switch-off command instantaneously forward onto.

Both electron tubes and transistors can be used to advantage for this purpose.
A currentless switch opening can also be achieved according to the invention that the switching element 11 is actuated by a DC converter arranged in the circuit belonging to it, this switching element then having to have the effect of a relay equipped with a make contact. In this case, the actual current flowing in the valve path is used as a measure for the permissibility of a switch opening. This arrangement has the advantage that even if the blocking capacity of a valve path fails, i.e. in the event of reverse current as a result of the breakdown of all series-connected semiconductor elements of a valve path belonging to a current path or when a gas discharge vessel is reignited, opening a switch under current is definitely avoided.

The two types of actuation of the coincidence element mentioned can also be combined with one another will. In this case the coincidence element has three switching elements. This ensures that a Switch opening only in a certain part of one Period, namely the blocking phase, and also only possible when there is no reverse current in the to interrupting circuit flows. As a criterion for the currentlessness of the valve section can be a modification of the invention also utilize the blocking voltage occurring at the valve in the blocking phase. In this case, the switching element 11 is z. B. actuated by the reverse voltage, which may still a DC voltage, for example with the help of a potentiometer 17 or a towards the end of the The blocking phase starting, the blocking voltage counteracting voltage pulse is superimposed.

The invention is not tied to a specific embodiment of the switch 1. There are basically suitable all switches with a sufficiently short operating time for which tripping is indirect or direct is effected.

The invention is also not limited to the described mode of operation of the coincidence element. the Coincidence of the occurrence of an overcurrent and the currentlessness of the valve section in question can also be determined by comparing the magnetic forces of the two currents. For example the switch triggering magnet system can be designed so that the armature in opposite direction under the magnetic force on the one hand the load current of the Plant and on the other hand the current is in the valve section concerned, so that the armature is only in Movement occurs when at the same time the load current exceeds a predetermined maximum value and the valve section is de-energized.

The invention is of particular importance in rectifier systems with semiconductor valves, but it is also Can be used with advantage in systems with mercury vapor converters that do not allow grid blocking, in which case the switches are to be arranged in the anode lines.

Claims (6)

Patent claims: 1. Arrangement for overcurrent and short-circuit current interruption in rectifier systems extremely fast switches assigned to the individual valve circuits, each during the blocking phase the valve path in question are opened, characterized in that the opening of each this switch is effected by a coincidence element whose one input variable is the information the information about an existing overcurrent and one or more other input variables represent about the currentlessness of the assigned valve section, with the command for The switch opens when the input variables coincide. ίο 2. Arrangement according to claim 1, characterized in that for information about the coincidence element The half-waves of one with the operating voltage via the currentlessness of the assigned valve section synchronous alternating voltage with the corresponding phase position, the other half-waves of which are suppressed by a valve. 3. Arrangement according to claim 1, characterized in that for information about the coincidence element the output voltage of an im Circuit of these valve sections lying direct current converter is used. 4. Arrangement according to claim 1, characterized in that for information about the coincidence element about the currentlessness of the assigned 20th Valve section the blocking voltage applied to the valve section itself is used. 5. Arrangement according to claim 1, characterized in that for the information of the coincidence element consisting of three switching elements about the currentlessness of the associated valve path, both the half-waves of an alternating voltage synchronous with the operating voltage of the corresponding phase position, the other half-waves of which are suppressed by a valve, as well as the Output voltage of a DC converter located in the circuit of the assigned valve section. 6. Arrangement according to one of the preceding claims, characterized in that the magnet system of the switch using opposing magnetic forces as a coincidence element serves. Considered publications:
German patent application Z 1560 VIIIb / 21c (published on May 21, 1953). Legacy Patents Considered:
German Patent No. 1 041 140. 1 sheet of drawings © 009 530/422 6.