Abstract: In a disclosed system, yaw rotation is generated by motors, the output torque of which is maintained substantially constant when the motor speed is within a predetermined range, to reduce the variation in the output torque. In another system, yaw rotation is generated by pinion gears each controlled by a motor mounted on the tower of the generator and arranged to rotate a main gear wheel attached to the nacelle. To prevent wear on the motors arising from differences in backlash between the pinion gears and the main gear wheel, each motor is controlled to generate a low output torque until all pinion gears have engaged the main gear wheel, after which the full output torque is applied to all motors. In a further system, braking is arranged to be provided either by mechanical brakes or by generating a counter-torque in the motors, in dependence on the sensed external load.

Abstract: A yawing system (2) for a wind turbine and a method of operating the yawing system (2) are disclosed. The yawing system (2) comprises at least one yaw drive arranged to cause the yawing system (2) to perform yawing movements, a yaw bearing allowing mutual movement between two parts of the yawing system (2) during yawing movements, and a hydraulically driven preload mechanism (1) being adapted to provide an adjustable pre-load force to the yaw bearing. The preload mechanism (1) is automatically operated as a consequence of operating the yawing system (2). Thereby it can be ensured that the preload force is adjusted in accordance with whether yawing movements are being performed, or the position of the nacelle should be maintained. The preload mechanism (1) may be modular, in the sense that two or more preload mechanisms (1) operate independently of each other, thereby providing redundancy.

Abstract: Systems for controlling yaw rotation of a horizontal-axis wind turbine generator are provided. In one system, yaw rotation is generated by motors 10, the output torque of which is maintained substantially constant when the motor speed is within a predetermined range, so as to reduce the variation in the output torque. In another system, yaw rotation is generated by pinion gears 9 each controlled by a motor 10 mounted on the tower of the generator and arranged to rotate a main gear wheel 8 attached to the nacelle. To prevent wear on the motors 10 arising from differences in backlash between the pinion gears 9 and the main gear wheel 8, each motor 10 is controlled to generate a low output torque until all pinion gears 9 have engaged the main gear wheel 8, after which the full output torque is applied to all motors 10.

Abstract: A yawing system (2) for a wind turbine and a method of operating the yawing system (2) are disclosed. The yawing system (2) comprises at least one yaw drive arranged to cause the yawing system (2) to perform yawing movements, a yaw bearing allowing mutual movement between two parts of the yawing system (2) during yawing movements, and ahydraulically driven preload mechanism (1) being adapted to provide an adjustable pre-load force to the yaw bearing. The preload mechanism (1) is automatically operated as a consequence of operating the yawing system (2). Thereby it can be ensured that the preload force is adjusted in accordance with whether yawing movements are being performed, or the position of the nacelle should be maintained. The preload mechanism (1) may be modular, in the sense that two or more preload mechanisms (1) operate independently of each other, thereby providing redundancy.

Abstract: A wind turbine having a tower and a nacelle mounted on top of the tower. The turbine further includes a bearing for a yaw motion of the nacelle in relation to the tower, and a drive assembly for the yaw motion. The device assembly includes at least one power unit fixedly connected to the nacelle. The power unit has a motor and a wheel adapted to be driven by the motor and in engagement with a ring fixedly connected to the tower for effecting the yaw motion, wherein a region of engagement of the ring with the wheel is located separate from the bearing, characterized in that the motor is located below the wheel. Preferably, the bearing is a friction bearing comprising an insert portion fixedly connected to the nacelle, and a clamp portion fixedly connected to the tower and in clamping engagement with the insert portion.

Abstract: A wind turbine having a tower and a nacelle mounted on top of the tower. The turbine further includes a bearing for a yaw motion of the nacelle in relation to the tower, and a drive assembly for the yaw motion. The device assembly includes at least one power unit fixedly connected to the nacelle. The power unit has a motor and a wheel adapted to be driven by the motor and in engagement with a ring fixedly connected to the tower for effecting the yaw motion, wherein a region of engagement of the ring with the wheel is located separate from the bearing, characterized in that the motor is located below the wheel. Preferably, the bearing is a friction bearing comprising an insert portion fixedly connected to the nacelle, and a clamp portion fixedly connected to the tower and in clamping engagement with the insert portion.

Abstract: The invention relates to a self-oscillating circuit comprising comparator means (CM) comprising at least one input means (IM) and at least one output means (OM), at least one of said at least one output means (OM) is coupled to at least one of said at least one input means (IM) via at least one filtering means (FM), said at least one filtering means (FM) at least partly comprising demodulation means (DM), wherein said filtering means (FM) is of at least fifth order.

Abstract: An integrated laser device includes a pre-distortion circuit. The pre-distortion circuit receives an electrical modulation signal and generates a pre-distorted modulation signal. A laser is integral with the pre-distortion circuit. The laser includes an electrical modulation input that is connected to the output of the pre-distortion circuit. The laser modulates an optical signal with the pre-distorted modulation signal. The pre-distorted modulation signal causes at least some vector cancellation of distortion signals generated when the laser modulates the optical signal.

Abstract: A controlled oscillation modulator includes a comparator and a power amplification stage for pulse modulation, and a higher order oscillating loop comprising first feedback means (21) and first forward means (22) securing stable oscillating conditions. The modulator is characterized by current measurement means, arranged to measure a value (iL) of a current supplied by said power amplification stage to a load (5) connected to the modulator, said measured value being supplied to said first feedback means (21), wherein said first feedback means (21) has a transfer function adapted to generate said first feedback signal based on said measured value (iL), and said first forward means (21) has a transfer function adapted to generate said modulating signal based on said first feedback means and an input signal (Vi). Applications are general DC-DC and DC-AC power conversion with inductive loading. In a preferred embodiment the system implements a precision transconductance amplifier by a current feedback.

Abstract: A front display panel for an industrial process control instrument which acts to maintain a process variable, such as flow rate, at a desired value. The instrument compares a signal representing the variable with an adjustable set point to produce an output signal that reflects the deviation of the variable from the set point, the output signal being applied to a final control element such as a valve which governs the process variable. The front panel of the instrument includes a bar graph indicator for the process variable, a bar graph indicator for the set point and a bar graph indicator for the output signal, all three indicators being of the gas discharge type and being integrated into a single panel defining a sealed envelope filled with an ionizable gas and provided with electrodes. Also integrated into the panel are touch-sensitive switches and other control and indicating elements.