Prime-mover dynamo plants – Electric control – Fluid-current motors
Reexamination Certificate
1997-10-30
2001-01-23
Enad, Elvin (Department: 2834)
Prime-mover dynamo plants
Electric control
Fluid-current motors
C290S052000, C290S053000, C290S054000, C290S055000
Reexamination Certificate
active
06177735
ABSTRACT:
BACKGROUND
FIGS.
1
-
4
, inclusive, illustrate prior art systems.
FIG. 1
is a schematic illustration of a typical power conversion system
20
. Aerodynamic rotor
22
is connected via rotating shaft
24
to speed increaser gear box
26
. Aerodynamic rotor
22
typically operates at a rotational speed in the range of 20 to 300 rpms. Gear box
26
translates the rotational speed of shaft
24
into a relatively higher rotational speed of shaft
28
, which in turn is connected to conventional generator
30
. Power electronic control
32
is sometimes used to control the generator and to convert the generator's variable-voltage, variable-frequency power to a standard utility voltage and frequency. Utility grid
34
receives and stores the generator electricity for use.
Aerodynamic rotor
22
is usually a propeller-type rotor, such as rotor
40
in FIGS.
2
and (
3
). A plural of blades
42
are connected to and extend radially out from central hub
44
. Hub
44
is connected to a distal end of shaft
46
which rotates with hub
44
and blades
42
in response to wind W impinging on blades
42
.
FIG. 3
shows a front view of aerodynamic rotor
40
which optimally would receive wind from a direction normal to the plane of the figure.
There are two common types of speed increasers that are used in wind turbines, a gear box and a belt-and-pulley transmission. A speed increaser is required because there is a mismatch between the optimally-efficient operating speed of the aerodynamic rotor and the electric generator. The most efficient conversion speeds of most aerodynamic rotors are typically much lower than the optimally-efficient, rotational speeds of standard industrial electric machines such as squirrel-cage induction or synchronous generators. These machines are designed for relatively high-speed, low-torque operation. For example, the standard four-pole induction or synchronous machine operates at 60 Hz at a nominal speed of 1800 rpm. In contrast, depending on the power level of the aerodynamic rotor operating in air, the aerodynamic rotor may have an operating speed in the range of 20 rpm to 300 rpm. Depending on the wind speed regime, the 20 rpm speed may apply to rotors designed to deliver 600 kW to 1000 kW of shaft power. Similarly, the 300 rpm speed might apply to much smaller rotors designed to deliver 2 kW to 10 kW. Use of a speed increaser significantly increases the number of required parts, cost of manufacturing, complexity of ultimate design and potential for mechanical failure. Use of a speed increaser also results in a loss of power conversion efficiency.
Wind turbines have been manufactured which do not require speed increasers to translate shaft rotational speed between an aerodynamic rotor and a generator. Such systems are referred to as “direct-drive wind turbines.” For example, as shown in
FIG. 4
, power conversion system
70
employs a propeller-type aerodynamic rotor
72
connected via rotary shaft
74
to direct drive generator
76
. Shaft
74
rotates with rotor
72
. Shaft
74
is supported by bearings (not shown). The main shaft support bearings can be located on the shaft in a pillow-block arrangement or can be located within the gear box. Power conversion system
70
is a variable-speed configuration which employs power electronic control
78
to control the generator and to convert the generator's variable-voltage, variable-frequency power to a standard utility voltage and frequency.
An object of the invention is to provide a simple, manufacturable and efficient system for interconverting moving fluid power and electrical power.
A more specific object of the invention is to efficiently convert fluctuating wind power into electricity.
Another object of the invention is to provide a wind turbine which does not require a speed-increaser to couple the torque and power from an aerodynamic rotor to an electric machine.
Still another object of the invention is to employ a shaft and support bearing configuration for an aerodynamic rotor which eliminates the fluctuating bending moments which occur when a shaft is required to support and rotate with an aerodynamic rotor.
REFERENCES:
patent: 4064403 (1977-12-01), Miller
patent: 4134707 (1979-01-01), Ewwers
patent: 4220870 (1980-09-01), Kelly
patent: 4494007 (1985-01-01), Gaston
patent: 4616298 (1986-10-01), Bolson
patent: 4831297 (1989-05-01), Taylor et al.
patent: 5083040 (1992-01-01), Whitford et al.
patent: 5209650 (1993-05-01), Lemieux
patent: 5289042 (1994-02-01), Lis
patent: 5506453 (1996-04-01), McCombs
patent: 5591004 (1997-01-01), Aylor
patent: 5696419 (1997-12-01), Rakestraw et al.
Chapman Jamie C.
Peterka Jon A.
Enad Elvin
Kolisch Hartwell Dickinson & McCormack & Heuser
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