Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-07
2001-08-21
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S10200A, C310S184000
Reexamination Certificate
active
06278212
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an exciter with axial gap for providing power to, for example, a synchronous machine such as a motor or generator.
Conventional exciters typically have a concentric rotor and stator for providing high voltage, low current power to a synchronous machine. The size of a conventional exciter is typically about 10% of the machine being powered.
Power to a superconducting synchronous machine is provided at low voltage and high current. Exciter power is typically provided to a superconducting synchronous machine by an exciter having a concentric rotor and stator connected to a shaft extending out of the machine housing.
SUMMARY OF THE INVENTION
The exciter of the present invention has a unique configuration for providing low voltage, high current power to, for example, a superconducting synchronous machine. In addition, the size and configuration of the exciter permits it to be located directly in the machine housing.
According to one aspect of the invention, an exciter includes a concentrically laminated rotatable disk including AC windings, and a stationary disk including a plurality of DC excitation poles with DC excitation windings. The stationary disk is axially spaced from the concentrically laminated disk to form a gap therebetween. Upon rotation of the concentrically laminated disk, a DC current applied to the DC excitation poles produces an AC current in the AC winding.
Embodiments of this aspect of the invention may include one or more of the following features.
A rectifier is coupled to the AC windings of the concentrically laminated disk to produce a DC exciter current. The plurality of DC excitation poles are on a first face of the stationary disk. On a second face of the stationary disk are pilot AC windings. A second rectifier includes an output coupled to the DC windings and an input coupled to pilot AC windings. A current regulator is electrically disposed between the pilot AC windings and the DC windings. The stationary disk, rectifier and current regulator are mounted to a frame.
In certain illustrated embodiments, the exciter includes a pilot disk including permanent magnets. The pilot disk is spaced from the second face of the stationary disk to form a gap therebetween. Upon rotation of the pilot disk, an AC current is created in the pilot AC windings.
The pilot disk and the concentrically laminated disk are mounted to a shaft for rotation therewith. The stationary disk is also concentrically laminated.
According to another aspect of the invention, a synchronous machine includes a stator, a rotor, and a disk-shaped exciter electrically coupled to the rotor. The disk-shaped exciter has a concentrically laminated rotatable disk including AC windings and a stationary disk including a plurality of DC poles with DC excitation windings. Upon rotation of the concentrically laminated disk, a DC current applied to the DC excitation windings produces an AC current in the AC windings.
According to another aspect of the invention, an exciter for a synchronous machine includes a stationary disk with a plurality of DC excitation poles with DC excitation windings on a first face of the disk and pilot AC windings on a second face of the disk. A rectifier is coupled between the pilot AC windings and the DC excitation windings.
According to another aspect of the invention, a housing encloses a superconducting machine and a disk-shaped exciter. The superconducting machine has cooled superconducting windings. The disk-shaped exciter is sized to fit within the superconducting machine housing. For a small machine of, for example, 5000 hp, the ratio of the overall length of the superconducting machine to the overall length of the disk-shaped exciter is at least about 4:1. For larger machines, the ratio will typically be about 10:1.
According to another aspect of the invention, the disk-shaped exciter for a synchronous machine includes a brushless pilot exciter including permanent magnets mounted in relative rotation with respect to a second face of a disk having concentric laminations and including a plurality of DC excitation poles on a first face of the disk and AC windings on the second face of the disk.
In another aspect, the invention features a method for providing an exciter current. The method includes providing power to a plurality of DC excitation windings on a first face of a stationary disk, and rotating a concentrically laminated disk axially spaced from the stationary disk at a fixed distance. The concentrically laminated disk including AC windings facing the DC excitation windings such that an AC voltage is produced in the AC windings upon relative rotational movement of the disks.
Embodiments of this aspect of the invention may include one or more of the following features.
The method for providing an exciter current includes rotating a pilot disk including permanent magnets spaced from a second face of the stationary disk by a fixed second distance. The second face of the stationary disk includes pilot AC windings and the rotation of the pilot disk produces a pilot AC current in the pilot AC windings. The pilot AC current is rectified to produce a DC current for powering the DC excitation poles. The method includes rotating the concentrically laminated disk and the pilot disk at the same rate. The concentrically laminated disk and the pilot disk are connected by a shaft.
According to another aspect of the invention, a method for providing an exciter current includes rotating the pilot disk and the concentrically laminated disk at different rates.
According to another aspect of the invention, a method for providing an exciter current includes connecting a first concentrically laminated disk having AC windings to a second disk having permanent magnets such that the first and second disks rotate at the same rate; disposing in between the first and second disks, a plurality of stationary DC excitation poles facing the first disk and stationary pilot AC windings facing the second disk, such that the DC excitation poles are spaced apart from the AC windings by a first fixed distance, and the stationary pilot AC windings are spaced apart from the permanent magnets by a second fixed distance; rectifying a pilot AC current generated in the pilot AC windings, and providing the rectified current to the DC excitation poles, such that an AC current is generated in the AC windings.
Among other advantages, the exciter is electrically self-contained rendering an external power supply unnecessary. The exciter is brushless, thereby eliminating the need for periodic replacement and maintenance of brushes. The exciter is also significantly more compact than conventional exciters permitting the exciter of the invention to be accommodated in the same housing as the synchronous machine being powered.
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American Superconductor Corp.
Fish & Richardson P.C.
Nguyen Tran
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