Daimler Chrysler Ag

Bbc Brown, Boveri & Company, Limited

Hans-Jurg Wiesmann

Reinhard Fried

Tudor Baiatu

Peter Etter

Ulrich Kogelschatz

Peter Erni

Sigfrid Strassler

Current limiters, preferably PTC resistors, are used for limiting short-circuit current when connected in series to capacitors and converter valves. Protective devices operating with these PTC resistors are able to work reversibly and respond without arcing. They have a low inductance and can be used in space-saving designs. Protective circuits with such PTC resistors have a low loss, are shake-proof, and can be integrated into an existing cooling circuit. They respond autonomously and enable a flexible application. The PTC resistors preferably are constructed in a meander shape of porous metal foam or a metal braid or fabric and have electrical contact bridges between their resistor tracks. At least 2 resistor tracks that are electrically connected in parallel are arranged at a small distance on top of each other in such a way that partial currents (I1, I2) flow in opposite directions through resistor branches in superposed track areas formed in this manner. The resistor tracks can also be arranged in grooves of a cooling body or may have a circular shape. A compensation resistor for compensating uncompensated marginal areas of these resistor tracks can be provided in serial connection to meander-shaped, parallel connected resistor tracks.

Overcurrent limiter having inductive compensation

An ozone-generating element is disclosed which has a tube ozonizer (1), consisting essentially of an outer metal tube (3) forming one electrode, and of a glass tube (4) which is located coaxially therein and is spaced from it and the inner surface of which is provided with an electrically conductive layer (5) serving as the other electrode. Ozone is formed by pulse discharges with a passive, plate-like spark gap (12) with a defined response voltage serving as a switching element. The tube ozonizer (1) is fed by a low-frequency current source (7) via a high-voltage transformer (9), to the secondary winding (10) of which a storage capacitor (11) is connected. A series of embodiments is proposed, and in these part or all the constructional elements of the critical pulse circuit form a constructional unit with, or integrated into, the tube ozonizer (1). In this way, it is possible to produce pulse circuits of extremely low inductance which lead to up to a doubling of the total efficiency of ozone generation. By means of the highest integration stage which is considered especially advantageous, it becomes possible to convert conventional ozone generators fed with alternating current to pulse operation, without having to carry out expensive conversion and adaptation work, especially in terms of circuitry.

Apparatus for generating ozone by an electric discharge

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Seegraben, Switzerland

Hans-Jurg Wiesmann