Stromrichterantrieb

摘要

A power converter drive for working aggregates with a propeller characteristic, for example marine screw propellers, has a synchronous motor with one or two stator windings, frequency converters for feeding the stator windings from a three-phase network and a regulating and controlling device (36) for the frequency converters and synchronous motor (19) associated to a manually controlled speed of rotation set value regulator (38). The frequency converters may be designed as direct or indirect frequency converters. When they are designed as indirect frequency converters (22, 23), they have two current source converters (32, 33) interconnected in series, associated each to one stator winding and that consist each of controlled semiconductor switches in a three-phase bridge arrangement. A current inverter (34) at the motor side with controlled semiconductors in a three-phase bridge arrangement is connected by a direct current intermediate circuit to the power converters (32, 33). In order to improve the power factor in the medium to low range of speeds of rotation of the power converter drive, one current source converter (33) of each pair of current source converters (32, 33) interconnected in series is short-circuited by a control unit (37) when the speed of rotation of the synchronous motor (19) falls below a set speed of rotation down to a predetermined speed of rotation (threshold speed of rotation), reducing the voltage in the intermediate circuit of the frequency converter (22 or 23) that feeds the stator winding of the synchronous motor (19).