This present invention relates to an electric fin and a water sports instrument, wherein the electric fin comprises a housing extending along a first direction and having a water inlet cavity; and a propeller and a guide member sequentially arranged in the first direction, wherein the propeller is located in the water inlet cavity, at least part of the guide member is located in the water inlet cavity, the water flow in the water inlet cavity flows out of the guide member; the propeller is provided with a propeller shaft and a plurality of blades, the propeller shaft extends in the first direction, and the plurality of blades are arranged on the propeller shaft in the circumferential direction; the guide member is provided with a guide shaft and a plurality of flow deflectors, the guide shaft extends in the first direction and the plurality of flow deflectors are arranged on the guide shaft in the circumferential direction; the outer contour enclosed by the propeller shaft and the guide shaft shows a projection in a second direction, whose size in a third direction gradually decreases along a fourth direction. The electric fin of the present invention has sufficient power and good guiding performance.

A method for operating a propulsion device having a propulsor with a propeller, the propulsion device having a base coupled to a marine vessel and being configured to propel the marine vessel in water. The method includes moving the propulsor from a deployed position towards a stowed position, where the propulsor is closer to the marine vessel in the stowed position than in the deployed position, and where the propulsor is configured to propel the marine vessel in the deployed position. The method further includes rotating the propeller so as to fit between sides of the base coupled to the marine vessel when the propulsor is in the stowed position.

A method for operating a propulsion device having a propulsor with a propeller, the propulsion device having a base coupled to a marine vessel and being configured to propel the marine vessel in water. The method includes moving the propulsor from a deployed position towards a stowed position, where the propulsor is closer to the marine vessel in the stowed position than in the deployed position, and where the propulsor is configured to propel the marine vessel in the deployed position. The method further includes rotating the propeller so as to fit between sides of the base coupled to the marine vessel when the propulsor is in the stowed position.

An arrangement for power distribution on a vessel, having: a first DC bus operating at a first medium voltage; at least one second DC bus operating at a second medium voltage and having no direct connection with the first DC bus; a first AC bus operating at a low voltage; a first inverter coupled between the first DC bus and the first AC bus for allowing power flow from the first DC bus to the first AC bus in a first operation mode; a second AC bus operating at the low voltage; a second inverter coupled between the second DC bus and the second AC bus for allowing power flow from the second DC bus to the second AC bus in the first operation mode; a low voltage connection system for selectively connecting or disconnecting the first AC bus and the second AC bus.

A method of controlling power transfer in a power system including a main bus, having a first and second bus sections, the first bus section connectable to the second bus section, first and second power generating units connectable to the first and second bus sections, a first and second drive systems connectable to the first and second bus sections, a central energy storage system, and a control system. The first and second drive systems include first and second bi-directional power converters connectable to the central energy storage system, and wherein the control system is arranged to control the first bi-directional power converter to transfer power from the first drive system to the central energy storage system, and to control the second bi-directional power converter to transfer power from the central energy storage system to the second drive system.

A system includes at least one compressor, at least two turbines, and at least two combustors, each fluidically coupled to a respective turbine of the at least two turbines and configured to receive compressed fluid from the at least one compressor. The system further includes at least two motor-generators, each operably coupled to a respective turbine of the at least two turbines and configured to convert electrical energy to mechanical energy to drive a respective propulsor to which the respective motor-generator is operably coupled and to convert mechanical energy from the respective turbine to electrical energy. The system further includes at least two propulsors, each operably coupled to a respective turbine of the at least two turbines and configured to be driven by the respective turbine, a respective motor-generator to which the respective propulsor is operably coupled via the respective turbine, or both the respective turbine and the respective motor-generator.

A watercraft and associated pedal drive system are provided. Method of operating the pedal drive are also provided. The pedal drive system allows for unassisted manual pedaling to provide thrust to the watercraft. The pedal drive system also provides on demand pedal assistance of varying levels via an assist drive train having an electric motor to supplement the manual pedal force input provided by a user at the pedals of pedal drive system.

An electric power generation system and a method in an electric power generation system. The system comprising one or more generators for producing electrical energy, each generator being arranged to be driven with a corresponding prime mover, wherein the generators are multiphase AC generators adapted to generate a multiphase voltage having a frequency and an amplitude, the phase outputs of the generators are connectable to a common multiphase bus for distributing the electrical energy generated by the AC generators, the system comprises further means for providing independent reference values for a rotational speed of the prime movers and for amplitude of the multiphase voltage, the rotational speed of the prime movers defining the frequency of the multiphase voltage, and the system is adapted to operate in at least three operation points on the basis of the provided independent reference values, an operation point being defined by a ratio of the amplitude of the multiphase voltage to the frequency of the multiphase voltage, wherein the at least three operation points are different.

An electric power generation system and a method in an electric power generation system. The system comprising one or more generators for producing electrical energy, each generator being arranged to be driven with a corresponding prime mover, wherein the generators are multiphase AC generators adapted to generate a multiphase voltage having a frequency and an amplitude, the phase outputs of the generators are connectable to a common multiphase bus for distributing the electrical energy generated by the AC generators, the system comprises further means for providing independent reference values for a rotational speed of the prime movers and for amplitude of the multiphase voltage, the rotational speed of the prime movers defining the frequency of the multiphase voltage, and the system is adapted to operate in at least three operation points on the basis of the provided independent reference values, an operation point being defined by a ratio of the amplitude of the multiphase voltage to the frequency of the multiphase voltage, wherein the at least three operation points are different.

A rotor for a permanent magnet machine includes first and second axially successive rotor sections each including permanent magnets generating magnetic field having a pole pitch. The rotor includes a first coupling system for connecting the first rotor section to a shaft and a second coupling system for connecting the second rotor section to the shaft or to the first rotor section. The second rotor section is rotatable with respect to the first rotor section by an angle corresponding to the pole pitch in response to releasing the second coupling system so as to set the stator flux-linkages generated by the first and second rotor sections to be substantially zeroes. Thereafter, the permanent magnets do not substantially induce voltages on the stator windings even if the rotor is rotating during for example an internal fault of stator windings.