Abstract: The present invention relates to a vacuum switch assembly for interrupting and isolating fault current. The vacuum switch assembly includes first and second dc lines that, in use, are electrically connected to the dc output terminals of a primary dc power source and a dc network. Each dc line includes at least one vacuum switch having contacts that are opened and closed under the control of a vacuum switch controller. A passive dc power supply unit is electrically connected to the first and second dc lines and includes a secondary dc power source that provides a substantially ripple-free sensing voltage. The vacuum switch controller is adapted to open the vacuum switch contacts when a fault condition (e.g. a fault current or other fault) or an operator request has been identified and when the current flowing between the vacuum switch contacts is below a chopping current associated with the vacuum switches.

Abstract: Provided is a power conversion system that includes a first transformer adapted to be connected to an AC network, the first transformer including a first primary winding and two first secondary windings, and two power converters, each being connected to a first respective secondary winding. The system further includes a second transformer and a secondary electrical device, the second transformer including a second primary winding and two second secondary windings, each second secondary winding being connected to a respective first secondary winding, and the secondary device being connected to the second primary winding.

Abstract: An electrical machine 20, 48 comprises a first stator 22 and a second stator 24 spaced from the first stator 22, at least one of the first stator 22 and the second stator 24 including a guide arrangement 26, 50. The electrical machine 20, 48 also includes a plurality of rotor elements 30, 46 located between the first stator 22 and the second stator 24 and cooperating with the guide arrangement 26, 50 for movement relative to the first stator 22 and the second stator 24. Adjacent rotor elements 30, 46 cooperate with each other so that the rotor elements 30, 46 form a rotor and at least one of the rotor elements 30, 46 includes a coupling element 32 to transfer force to or from the rotor.

Abstract: A dc energy store includes auxiliary systems operable in different modes, including self-supporting, island mode and normal modes. In the self-supporting mode a first controller uses a voltage demand signal indicative of desired ac voltage of an AC/DC power converter to control semiconductor power switching devices to achieve the desired level of ac voltage. The voltage demand signal is derived from comparing a voltage feedback signal and a second voltage demand signal preset to provide the desired ac voltage for the auxiliary systems. A second controller uses a current demand signal indicative of the desired dc link current to control the semiconductor power switching devices of a DC/DC power converter to achieve the desired level of dc link current. The current demand signal is derived from comparing a dc link voltage demand signal indicative of a desired dc link voltage and a dc link voltage feedback signal.

Abstract: A power transmission and distribution system suitable for subsea electrical loads includes a primary dc transmission cable connected to an onshore AC/DC converter module that connects the onshore end of the cable to an ac supply network. The subsea end of the cable is connected to a primary subsea power distribution unit and includes a DC/DC converter module having a modular topology with a series of interconnected DC/DC converter units. The DC/DC converter module is connected between the cable and a primary dc distribution network. Secondary dc transmission cables and associated circuit breakers connect the primary subsea power distribution unit to secondary subsea power distribution units that are located near the subsea loads. Each secondary subsea power distribution unit includes a DC/DC converter module having a modular topology with a series of interconnected DC/DC converter units. Respective secondary dc distribution networks supply power to one or more subsea loads.

Abstract: A taut cable with a fiber optic cable with Bragg diffusion gratings allows a suitable driver circuit to determine the shape of the taut cable at a large number of points along its length. This enables the total 3-dimensional shape of the taut cable to be estimated and from which the position of the vessel relative to a seabed weight attached to the taut cable can be inferred.

Abstract: The present invention relates to a retaining band which provides outer reinforcement for the rotor assembly of a high speed electrical machine. The rotor assembly includes a plurality of circumferentially-spaced permanent magnet assemblies. A retaining band is fitted around the rotor assembly and applies a pre-load to the permanent magnet assemblies in the radial direction. The retaining band has a plurality of voids that are sized and shaped to provide the retaining band with a progressive spring stiffness in the radial direction. The voids are open before the retaining band is fitted and during the fitting process the retaining band is deflected in the radial direction so that the voids close up and the retaining band becomes substantially solid.

Abstract: A method of estimating the environmental force acting on a supported jack-up vessel is described. The vessel is positioned in a force determination position and the strain on at least one support leg of the jack-up vessel is measured while a first thrust is applied to the vessel. A second thrust is applied to the vessel while the vessel is maintained in the force determination position. The variation in the strain in the at least one support leg is monitored as the second thrust is applied and the strain is used to calculate an estimate of the environmental force acting on the vessel. The method allows a dynamic positioning (DP) system of the jack-up vessel to determine a suitable thrust to apply to the vessel as the support legs of the vessel are raised. By applying this suitable thrust the position of the vessel can be maintained when the vessel transitions from being supported by the support legs to being supported by water.

Abstract: A wind turbine typically includes a generator and a rotating mechanical system having a natural period. The present invention relates to a method of controlling generator torque that minimizes oscillations in the speed of the generator rotor. In the event of a grid fault or transient, or a fault in the power converter, the generator torque is decreased at a substantially constant rate with respect to time. The rate at which the generator torque is decreases is proportional to the nominal rated torque of the generator and inversely proportional to an integer multiple of the natural period of the rotating mechanical system.

Abstract: A reactive energy compensator is provided. The compensator is connected to an alternating electrical network including M phase(s), M being an integer greater than or equal to 1. The compensator includes M connection terminals, N banks of capacitor(s) capable of providing reactive energy, N being an integer greater than or equal to 2, N two-way voltage inverters, connected to each other in parallel and each connected to a unique capacitor bank, each inverter being able to convert a direct current into an alternating current including M phase(s) in one direction and the alternating current into direct current in the other direction, each inverter including first and second input terminals and M output terminal(s), the input terminals being connected to the corresponding capacitor bank, each output terminal corresponding to a phase of the alternating current and being connected to a corresponding connection terminal, and a device for balancing the voltage of the N capacitor banks.

Abstract: A method of operating a dual fed system is described where power is supplied to a electrical load from first and second ac busbars at a ratio that achieves a desired level of exhaust emissions such as nitrogen oxides (NOx), carbon dioxide (CO2) and other pollutants produced by the prime movers associated with generators. Preferably, the method may be used to operate a dual fed marine propulsion system wherein the electrical load is a thruster. Operating a dual fed marine propulsion system using the method of the present invention makes it possible to optimise thrust allocation between thrusters in a way that is similar to that used in conventional dynamic positioning (DP) systems and then share or allocate the required power between generators to minimise exhaust emissions.

Abstract: This set of roller bearings, which is a grounding bearing for a rotary machine, comprises a first-angular contact rolling bearing having a first outer race, a first inner race and first rolling elements, a second angular-contact rolling bearing having a second outer race, a second inner race and second rolling elements, a mount in which the first angular-contact rolling bearing and the second angular-contact rolling bearing are mounted. The first outer race and the second outer race are arranged in the mount either directly one beside the other or via the interposition of an intermediate member, the axial stiffness of which is greater than that of the mount and than those of the first and second outer races. Application for example to asynchronous motors.

Abstract: A high vacuum component, e.g. a vacuum chamber wall or a component that is operated or positioned within a vacuum chamber in use is described. The component is substantially formed of a layered material comprising a fibrous composite material layer having a surface that is coated with a copper intermediate layer and an impermeable outer layer of nickel. In use the outer layer is exposed to a high vacuum.

Abstract: A blade for a water current turbine rotor, which extends along a radial direction and comprises an outer surface, an inner surface, a leading edge, and a trailing edge. The leading edge is the edge of the blade that extends along the radial direction and is disposed upstream in the direction in which the water flows along the blade, while the trailing edge is the edge of the blade opposite the leading edge and is disposed downstream in the direction of flow. At least one portion of the blade has a profile comprising a thick portion and a thin portion, the cross section being perpendicular to the radial direction. The thick portion and the thin portion each have a maximum thickness along a direction perpendicular to the outer surface, the maximum thickness of the thick portion being at least four times greater than the maximum thickness of the thin portion.

Abstract: A reactive energy compensator that can be electrically connected to an AC electrical network, including at least one input direct voltage bus, at least one voltage inverter including switches and first and second capacitors having first and second voltages at their terminals, control means for the switches, including computation means capable of generating a target control current, means for combining the target control current and the output current from the inverter, means for transmitting a control signal capable of driving the switches, and correction means for the control signals of the switches, the correction means being capable of adding a balancing current to the target control current, the balancing current being able to correct the target control current so as to reduce the difference between the values of the first and second voltages, the target control current being increased for an even harmonic of the network frequency.

Abstract: A method of operating a power converter arrangement, the power converter arrangement includes a dc link and a dc load/source, an active rectifier/inverter having dc terminals connected to the dc link and is adapted to provide a variable dc link voltage between a maximum and a minimum limits, an interleaved buck converter having a plurality of converter circuits connected between the dc link and the dc load/source, wherein each converter circuit includes a first switch, a second switch, and a reactor, the method including determining one or more null values of dc link voltage with reference to the voltage across the dc load/source, and if a null value of dc link voltage is between the maximum and the minimum limits, controlling the active rectifier/inverter to provide a dc link voltage that is substantially the same as the null value of dc link voltage.

Abstract: A structural component that experiences a changing magnetic field during use is described. The structural component can be a stator bore tube, a stator tooth or stator support, for example. A stator bore tube is made of a multi-layered composite material with layers of unidirectional carbon fibre reinforced polymer (CFRP). The eddy current direction is along the axis of the stator bore tube. The carbon fibres in the CFRP layers are orientated along the circumferential direction of the stator bore tube.

Abstract: A multi-phase electric circuit including an electric machine and an inverter, wherein machine encompasses a rotor connected to the inverter via at least two brushes for each phase, wherein each of the brushes of each phase is connected to the inverter via a separate brush line.

Abstract: A static energy supply unit has an energy store connected to an ac supply network by a power converter. A unit controller for the static energy supply unit includes an amplitude controller, a phase controller and a frequency controller. These measure and record characteristics of the supply network and provide output signals indicative of the voltage characteristics for an operating condition of the supply network. A signal generator for generating a simulated output voltage signal for each phase of the supply network is provided. A comparator is used to compare the simulated output voltage signal for each phase and a measured voltage for a corresponding phase of the supply network. The controller controls the operation of the power converter to vary the amount of power that is supplied to the supply network from the energy store based on the comparison of the simulated output voltage signal(s) and the measured voltage(s).

Abstract: The present invention provides a method of controlling the position of a spread moored marine vessel (1). In particular, the method of the present invention substantially maintains the position of a spread moored vessel (1) in, or on the boundary of a target area (2) using thruster assistance. This is done by monitoring the position of the vessel and when the vessel (1) is positioned outside of the target area (2) applying a position correcting thrust (7) to the vessel (1) in the direction of an aim position located on the boundary of the target area (2) and when the vessel (1) is positioned within the target area (2) reducing the position correcting thrust (7) applied to the vessel (1) or maintaining the position correcting thrust (7) applied to the vessel (1) at zero. The present invention may also apply a damping thrust (7) to the vessel (1) in order to damp the positional variation of the vessel (1).