BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an electric short-circuit device. The necessity of short-circuiting (bridging) certain circuit parts sometimes arises in electric circuits. There are, for example, power converters that comprise a large number of electric modules connected in series. If one of the modules breaks down during operation, it is desirable to short-circuit (bridge) this defective module so that the other modules of the electric series circuit can continue to be operated.

An electric short-circuit device with a pyrotechnic drive is known from the international patent application WO 2011/107363 A1. The pyrotechnic drive enables fast closure of the short-circuit device, but sometimes causes problems related to safety (explosive material).

SUMMARY OF THE INVENTION

The invention is based on the object of providing a short-circuit device and a method for short-circuiting a module wherein no pyrotechnic drive is required.

This object is achieved according to the invention by an electric short-circuit device and by a method in accordance with the independent claims. Advantageous forms of embodiment of the short-circuit device and of the method are given in the dependent claims.

An electric short-circuit device (bridging device) is disclosedwith a first electric contact piece and a second electric contact piece,with a component made of an electrically semiconducting crystalline material which blocks a flow of electric current between the first contact piece and the second contact piece in at least one direction, andwith an (electric) actuator (drive element) that is designed to apply a mechanical force to the component in response to an electric trigger signal and thereby at least partly destroy the crystal structure of the component. The actuator can also be designed to apply a mechanical force to the component in response to the electric trigger signal and thereby destroy the material. As a result of the at least partially destroyed crystal structure of the semiconducting crystalline material said material loses its electrically blocking capacity, so that as a result a flow of electric current between the first contact piece and the second contact piece is enabled in the originally blocked direction. This process is also referred to as breakdown. Even just fine cracks or fractures in the crystal structure of the crystalline material can be sufficient to nullify the electrically blocking properties of the short-circuit device. It is, of course, however, also possible to break the semiconducting crystalline material into a plurality of fragments (visible with the naked eye) by means of the mechanical force. The actuator is, in general, an element that converts an electric signal into a mechanical movement.

The short-circuit device can be designed such that the component is arranged between the first contact piece and the second contact piece. The component can, in particular, be clamped between the first contact piece and the second contact piece. In the short-circuited state the electric current advantageously flows from one of the contact pieces through the component to another of the contact pieces, depending on the direction of the current.

The short-circuit device can be designed such that the short-circuit device is designed as a disk cell. The short-circuit device can in this way be designed to be mechanically very compact and robust. The first contact piece and the second contact piece here are essentially aligned parallel to one another.

The short-circuit device can also be designed such that the first contact piece comprises a first recess in which the actuator is arranged. The actuator arranged in the first recess can directly act mechanically on the component.

The short-circuit device can also be designed such that the second contact piece comprises a second recess that is arranged opposite the first recess. The second recess allows the component to deform in response to the mechanical force. This has the effect that the crystal structure of the component is partially destroyed in response to the mechanical force.

The short-circuit device can be designed such that the component separates the first recess from the second recess.

The short-circuit device can also be designed such that the component is a disk (made of the electrically semiconducting crystalline material). Such a disk is also referred to as a wafer. Because disks of this sort can be made comparatively thin, it is possible to destroy the crystal structure of the crystalline material with a comparatively small actuator and/or a small electric trigger signal.

The short-circuit device can be designed such that the component comprises at least one p-n junction, in particular two p-n junctions, aligned in opposite directions.

If the component only comprises one p-n junction (that is if the component, for example, corresponds to an electric diode), then when in not in the short-circuiting state it is able to block the electric current in one direction. If the component comprises two p-n junctions with opposite orientations (that is if the component, for example, corresponds to a thyristor), then when not in the short-circuiting state the component is able to block electric current in both directions.

The short-circuit device can also be designed such that the at least one p-n junction is a planar p-n junction that is aligned parallel to the first electric contact piece and/or parallel to the second electric contact piece. By means of one or a plurality of such planar p-n junctions even large electric currents can be carried safely when the short-circuit device is in the short-circuiting state.

The short-circuit device can also be designed such that the actuator is an (electric) piezo actuator. A piezo actuator of this sort has, in particular, the advantage that it generates a mechanical movement very quickly in response to the electric trigger signal, and is therefore able to apply the mechanical force to the component very quickly in response to the electric trigger signal.

The short-circuit device can also be designed such thatthe component is an electrically switchable semiconductor element (in particular a thyristor) whose control terminal (in particular its gate terminal) is brought out of the short-circuit device, so that the semiconductor component can also be switched on (electrically) by means of its control terminal.

A power converter with a plurality of (identical) two-pole modules (submodules) that are connected electrically in series is furthermore disclosed, wherein a respective electric short-circuit device according to one of the variants described above is assigned (in particular connected in parallel) to each of the modules (so that the modules can be short-circuited (bridged) by means of the short-circuit device respectively assigned to them).

This power converter can, in particular, be a modular multilevel power converter.

A method for short-circuiting an electric two-pole module is furthermore disclosed, wherein an electric short-circuit device that comprises a first electric contact piece, a second electric contact piece and a component made of an electrically semiconducting crystalline material is connected in parallel with the module, wherein in the methoda flow of electric current between the first contact piece and the second contact piece is initially blocked by the component in at least one direction,the component is subjected to a mechanical force by an actuator in response to an electric trigger signal, andthe crystal structure of the component is thereby at least partially (mechanically) destroyed, as a result of which (the component breaks down and) the flow of electric current between the first electric contact piece and the second electric contact piece in the originally blocked direction is enabled.

This method can be designed such that the electric module comprises at least two electronic switching elements and an electric energy store.

The method can also be designed such that the electric module is a module (submodule) of a modular multilevel power converter.

The method can also be designed such that the component is a disk (made of the electrically semiconducting crystalline material).

The short-circuit device can be designed such that the actuator is an (electric) piezo actuator.

The method has the same advantages as are presented above in connection with the short-circuit device.

