Abstract: A redundant cooling device, for an electrical submarine drive motor, includes a first cooling circuit and a second cooling circuit, by which thermal energy may be removed from the electric submarine drive motor. A high degree of operational security and redundancy may be provided, whereby the coolant in the first cooling circuit and the second cooling circuit flow counter-currently through a stator cooling circuit in the region of the electrical submarine drive motor.

Abstract: A method is for controlling a multi-phase electrical ship propulsion motor that is supplied with electric energy via a power converter. The ship propulsion motor is preferably a permanently excited motor with at least three windings. The phase currents flowing in the windings are controlled via the power converter to minimize the body noise emitted by the electrical ship propulsion motor.

Abstract: Please replace the Abstract with the attached revised Abstract located at the end of this document.

Abstract: A polyphase machine fed by a pulse-controlled a.c. converter in which the current is controlled between rectangular and sine-shaped waveforms in each half cycle according to the required torque. Independently of the current control, the active number of phase windings is reduced as a function of the rotational speed of the machine.

Abstract: A low-loss and low-reactive power switching relief circuit has an inverter output section coupled at its upper and lower ends to the positive or negative potential of a DC voltage source, respectively. The coupling is via saturable stepping choke coils. A wiring network serves as a switching relief for the semiconductor switches of each inverter phase. A circuit having a switching-off relief capacitor, two storage capacitors and two switching-off relief diodes causes uniform switching-off relief. A circuit having two current rate of rise limiting choke coils and four feedback diodes causes uniform switching-on relief of the upper and lower semiconductor switches, respectively. By means of the stepping choke coils, the output section and the wiring network are temporarily decoupled from the DC voltage source during the switching-on process of one of the semiconductor switches. This occurs in such a manner that the interim-stored trapped energy is fed into the load nearly without loss and any reactive power.

Abstract: An electrical machine driven by a pulse-controlled a.c. converter contains multiple phases subdivided into a number of n.gtoreq.2 equivalent phases sections that are extensively magnetically decoupled relative to each other. Each phase section is fed by a separate frequency converter. The clocking of the frequency converters for the n phase sections ensues out of phase by an angle of 2.pi./n relative to each other phase section.

Abstract: A short-circuit protective device for a motor-driven and generator-driven electrical machine fed by a pulse-controlled a.c. converter has reverse-parallel circuitry that is switching dependent on a monitoring device. The monitoring device detects short circuits and is provided in a d.c. current supply line. Using the reverse-parallel circuitry and the monitor, an intermediate circuit capacitor of the pulse-controlled a.c. converter feeding the machine is isolated from the short circuit location.