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AssigneeCarter Wind Power
InventorsJ. Warne Carter, Jr., J. Warne Carter, Sr.
Estimating the term…
Wind generator apparatus employs an induction generator with a wind-driven rotor. Connection of the induction generator to AC power lines is controlled by apparatus that compares generator rpm and line frequency. The rotor blades have a pretwisted, varying-chord inboard portion and an untwisted, constant-chord outboard portion. The blades are self-starting, operate efficiently over a range of wind speeds with constant pitch maintained by a torsional biasing mechanism, and pitch up automatically when the normal rpm operating range is exceeded. An improved blade-supporting spar of low torsional stiffness has an I-beam configuration with filament-wound flanges. A pitch damper prevents torsional oscillations while permitting the blades to pitch up readily. The rotor, which includes a teetering hub, is free to weather-vane about the axis of a supporting tower, but a yaw damper limits angular velocity. A guy wire and gin pole arrangement stabilizes the tower and permits easy raising and lowering of the tower.
In wind-driven generator apparatus, a rotor blade comprising an inboard portion and an outboard portion, the blade being shaped so that at rest the inboard portion has a substantial average pitch and the outboard portion has less average pitch than the inboard portion, the outboard portion being a substantially constant-chord portion and the inboard portion having a chord that increases as the root of the blade is approached.
In wind-driven generator apparatus a rotor blade comprising an airfoil which at rest is twisted about a longitudinal twist axis and has a blade-supporting spar extending along the twist axis interiorly of the airfoil, an inboard part of the airfoil being hollow with the spar extending therein and free to twist relative thereto, the spar being embedded over an outboard part of its length in an outboard part of the airfoil.
Wind-driven generator apparatus having a rotor with at least one rotor blade, the blade comprising an airfoil configured and disposed relative to a plane of rotation of the rotor in a manner causing centrifugal force which acts on the blade when it rotates to produce a twisting force on the blade tending to change the pitch of the blade about a longitudinal blade axis, and pitch fixing means associated with the blade for preventing the twisting force from changing the blade pitch until the twisting force exceeds a predetermined value dependent on the rotational velocity of the blade and allowing the twisting force to change the blade pitch when said predetermined value is exceeded, wherein said predetermined value corresponds to a normal velocity of the rotor and wherein the pitch fixing means includes spring biasing means which fixes the pitch at all times except when the normal velocity is exceeded.
In wind-driven generator apparatus having a rotor blade wherein centrifugal force created when the blade rotates tends to change the pitch of the blade about a longitudinal blade axis, pitch fixing means for preventing centrifugal force from changing the blade pitch when the blade rotates at a normal velocity and for allowing centrifugal force to change the blade pitch when the normal velocity is exceeded, wherein the blade has a supporting spar including resin subject to creep when stressed and wherein the pitch fixing means fixes the pitch independently of the creep.
Wind-driven generator apparatus having a rotor with at least one rotor blade, the blade comprising an airfoil configured and disposed relative to a plane of rotation of the rotor in a manner causing centrifugal force which acts on the blade when it rotates to produce a twisting force on the blade tending to change the pitch of the blade about a longitudinal blade axis, and pitch fixing means associated with the blade for preventing the twisting force from changing the blade pitch until the twisting force exceeds a predetermined value dependent on the rotational velocity of the blade and allowing the twisting force to change the blade pitch when said predetermined value is exceeded, wherein said predetermined value corresponds with a normal rotational velocity of the rotor and wherein the blade pitches up when the blade rotates at a velocity greater than said normal rotational velocity.
In wind-driven generator apparatus having a rotor blade wherein centrifugal force created when the blade rotates tends to change the pitch of the blade about a longitudinal blade axis, pitch fixing means for preventing centrifugal force from changing the blade pitch when the blade rotates at a normal velocity and for allowing centrifugal force to change the blade pitch when the normal velocity is exceeded, wherein the blade has an airfoil and a supporting spar for the airfoil, and wherein the pitch fixing means comprises stop means connected to the root of the airfoil and means for biasing the root of the spar relative to the stop means, the biasing means being overcome by centrifugal force when the normal velocity is exceeded.
In wind-driven generator apparatus, a rotor having a rotor shaft, rotor blade means, and a teetering-hub supporting the blade means on the shaft for rotation with the shaft and for teetering movement relative to the shaft, a tower adapted to be mounted vertically, means for supporting the rotor at the top of the tower for rotation with the hub and blade means at one side of the tower, the supporting means permitting the rotor to weather-vane about the vertical axis of the tower, and fluid damping means for damping movement of the rotor about the vertical axis of the tower.
In wind-driven generator apparatus, a rotor shaft, rotor blade means, and a teetering hub supporting the blade means on the shaft for rotation with the shaft and for teetering movement relative to the shaft, wherein the blade means comprises a pair of pretwisted blades extending oppositely from the teetering hub with a predetermined initial coning angle therebetween, each blade comprising an inboard portion and an outboard portion and being shaped so that at rest the inboard portion has a substantial average pitch and the outboard portion has less average pitch than the inboard portion, the outboard portion being a substantially constant-chord portion and the inboard portion having a chord that increases as the root of the blade is approached.
In wind-driven generator apparatus, a rotor blade supporting spar having an elongate web with flanges that are formed by filaments extending longitudinally over longitudinal edges of the web, the filaments being embedded in a hardened matrix bonding said edges of the web to the flanges.
In wind-driven generator apparatus of the type having a rotor with a rotor blade that changes pitch in one direction responsive to centrifugal force acting on the blade when the blade rotates at a velocity above a predetermined velocity, and that then changes pitch in the opposite direction responsive to a reduction in centrifugal force, damper means that permits relatively free change of blade pitch in said one direction but that damps a change of blade pitch in the opposite direction.
In wind-driven generator apparatus of the type having an induction generator, control apparatus for controlling the connection of the generator to AC power lines, said control apparatus comprising means for producing a reference signal dependent upon the frequency of the AC power, means for producing a signal dependent upon the rotational velocity of the generator, and means responsive to the attainment of a predetermined relationship between said signals for connecting the generator to the AC power lines.
Wind-driven generator apparatus comprising a rotor that drives an induction generator, the rotor having blade means including an airfoil with an inboard portion and an outboard portion, the inboard portion being twisted about a longitudinal twist axis and having a chord that increases as the root of the airfoil is approached, the outboard portion being untwisted and having a constant chord, the blade means also including a blade-supporting spar extending along the twist axis interiorly of the airfoil, an inboard part of the airfoil being hollow with the spar extending therein and free to twist relative thereto, the spar being embedded in an outboard part of the airfoil, the blade means further including metal biasing means for providing a torsional bias that tends to twist the airfoil relative to the root of the spar, twist-stop means supported on the airfoil and against which the root of the spar is held in response to the torsional bias, and means for permitting the blade means to move about the twist axis so as to unseat the spar from the twist-stop means and thus to vary the effective pitch of the blade means, the blade means having a predetermined pitch that remains fixed until the blade means reaches a predetermined rotational velocity, whereupon the blade means pitches up in response to centrifugal force and unseats the spar from the twist-stop means, the spar being torsionally soft so that the blade means pitches up readily, the blade means also including damper means for damping torsional oscillations of the spar, and control apparatus for controlling the connection of the generator to AC power lines, the control apparatus comprising means for connecting the induction generator to the AC power lines only when the rotational velocity of the generator exceeds synchronous speed.
Wind-driven generator apparatus having a rotor with at least one rotor blade, the blade comprising an airfoil configured and disposed relative to a plane of rotation of the rotor in a manner causing centrifugal force which acts on the blade when it rotates to produce a twisting force on the blade tending to change the pitch of the blade about a longitudinal blade axis, and pitch fixing means associated with the blade for preventing the twisting force from changing the blade pitch until the twisting force exceeds a predetermined value corresponding to a normal rotational velocity of the rotor, and allowing the twisting force to change the blade pitch when said predetermined value is exceeded, thereby limiting the speed of the rotor.
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
This invention is concerned with improvements in the generation of electricity by wind power.
Shortages and increased cost of fossil fuels have stimulated renewed interest in the use of wind power to generate electricity. Electrical generators mechanically coupled to wind-driven rotors have been the subject of intense research and development, but problems of cost, reliability, efficiency, and safety have limited the adoption of such wind generator apparatus.
In an effort to accommodate a wide range of wind velocities, to provide self-starting blades, and to solve overload and overspeed problems, complex and expensive pitch changing mechanisms have been proposed. Fixed-pitch blades, while generally less expensive than variable-pitch blades, have not had the desired efficiency and safety and in some instances have not been self-starting. Manual or motor-driven yawing devices have often been required in order to orient rotors relative to the wind. Expensive cantilever tower support arrangements have been employed that are difficult to erect and that create difficulties in servicing the rotor and head assembly.
The invention will be further described in conjunction with the accompanying drawings, which illustrate a preferred and exemplary embodiment, and wherein:
FIG. 1 is a perspective view illustrating the appearance, overall, of wind generator apparatus in accordance with the invention;
FIG. 2 is a perspective view of a portion of the apparatus forming the head assembly of the wind generator;
Referring to FIG. 1 of the drawings, illustrative wind-driven generator apparatus in accordance with the invention comprises a rotor 10 supported on a tower 12. In the form shown the rotor has a pair of blades 14 and 16 and is part of a head assembly 18 mounted on the top of the tower. The tower base 20 is supported on the ground and is stabilized by guy wire elements 22, 24, 26, and 28. A gin pole 30 is employed in raising and lowering the tower, as will be described later.
As shown in FIG. 2, the head assembly 18 comprises a streamlined housing or pod 32 which may be formed of fiberglass, for example, and which may include upper and lower sections that are bolted together (the upper section being indicated in phantom lines). Located in the housing is an AC generator 34 driven by rotor 10 via a gear box 36. Head assembly 18 is supported on the tower for yawing movement about the longitudinal axis of the tower, and a slip ring unit 38 and associated brushes permit electrical connections to generator 34 and other electrical apparatus designated generally by reference numeral 40 without concern for the yawing movement of the head assembly.
AC generator 34 is preferably an induction generator, that is, an induction motor that is driven above synchronous speed, when the slip becomes negative. The induction generator cannot generate its own exciting current; the exciting current is supplied by AC power lines. The frequency and voltage of the induction generator are those of the AC lines to which it is connected for excitation. Details of the generator and its control will be set forth later.
Automatic control; Regulation: by means of a mechanical governor
Rotors: characterised by their aerodynamic shape
Characterised by their construction elements: arrangements for fixing wind-engaging parts to a hub
Adjusting aerodynamic properties of the blades: adjusting blade pitch
Term ended 28 Dec 1999 (estimated)
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