Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-30
2001-11-06
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S179000, C029S596000
Reexamination Certificate
active
06313556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to superconducting electromechanical rotating (SER) devices and, more particularly relates to an SER device having a stator assembly including a stator winding which is potted to an associated support. The invention additionally relates to a method of potting a stator winding of an SER device to the associated support.
2. Discussion of the Related Art
Recent advances in superconductivity have led to an increased interest in the development and commercialization of superconducting electromechanical rotating (SER) devices such as large electric generators and large electric motors including synchronous AC motors. The device includes a superconductive rotor having a vacuum jacket and a stator coaxially surrounding the rotor. The superconducting coils are disposed inside of the vacuum jacket on a coil support structure. The coil support structure and coils are cooled to a cryogenic temperature. One such device is the so-called high temperature superconducting (HTS) electromechanical device which uses a HTS winding in the rotor of the device rather than a low temperature superconducting winding. In the case of a synchronous AC motor, the stator and rotor of the typical SER device are configured such that the rotor is rotated synchronously by the rotating stator magnetic field.
The usual stator of an SER device consists of a winding formed from coils that are mounted in axially extending, peripherally-spaced slots in the inner radial surface of a support structure of the device and that are held in place by fixturing straight portions of the winding to the slots and by mechanical hangers and/or rope or fabric in the end winding areas. Because the SER device operates at a much higher magnetic flux level than other machines, it typically does not have magnetic teeth. Such a machine is referred to as an “air core” machine. In an air core machine, the hypothetical ideal stator would have 100% of the space between the back-iron and the rotor filled with copper. However, in practice, practical limitations are imposed on the copper content of an SER device. These practical limitations include the insulation thickness, the end winding length, the need to cool the winding, and coil manufacturing issues. These practical limitations represent a problem in SER stator winding design.
The usual stator winding topology used in SER devices is not the optimal solution to this problem. The usual stator winding has a so-called two-layer topology in which 1) the number of coils equals the number of slots in the support surface on which the stator winding is mounted and 2) each slot contains one section of two different coils. Windings having a two-layer topology require relatively long end windings. This problem is exacerbated if the gap between adjacent straight portions of the coils is decreased in an effort to increase the total effective copper content of the device because, as the gap is decreased, the end winding length is increased proportionally, theoretically tending to infinity when the gap tends to zero.
Another problem-associated with usual SER stator winding designs is that they are relatively difficult to mount on the support structure. The usual stator winding is formed from a plurality of coils inserted into the slots in the inner radial surface of the support structure. The stator winding is then fixed in the slots using topsticks at the straight sections of the coils and mechanical fasteners such as hangers and/or fabric or rope at the end winding areas. This mounting technique is cumbersome and highly labor-intensive. Stator winding mounting becomes increasingly difficult as the space between adjacent straight portions of the stator coils is progressively decreased in an effort to increase copper content and current density. In fact, at one point, further gap reduction, even if not precluded by cooling constraints or other constraints, is precluded by the physical spacing required to receive the mechanical fasteners between coil portions.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore a first principal object of the invention to provide a superconducting electromechanical rotating (SER) device having a stator which has a relatively high copper content and current density and which is connected to an associated support structure in a simple manner that minimizes or eliminates constraints on the available spacing between adjacent straight stator coil portions.
A second object of the invention is to provide a SER device that meets the first principal object and the stator of which has ample room at the ends of its winding for coil connections.
In accordance with a first aspect of the invention, these objects are achieved by providing a SER device, such as an AC synchronous motor, that includes a rotor and a stator. The rotor includes a rotor winding which is cooled with a cryogenic fluid so as to be rendered superconductive. The stator surrounds the rotor and is selectively energizeable with an electric current to drive the rotor to rotate. The stator includes 1) a support structure which surrounds the rotor and which has an inner radial surface which faces an outer radial surface of the rotor, and 2) a liquid-cooled stator winding mounted on the inner radial surface of the support structure so as to face the rotor with an air-gap formed therebetween. The stator winding comprises a multi-coil, one-layer winding which has a number of stator coils potted onto the support structure using a potting material which is disposed in gaps in the stator winding and between the stator winding and the inner radial surface of the support structure.
Preferably, the support structure, the stator winding, and the potting material form a single unitary mass lacking mechanical fasteners or tape holding the stator winding on its support structure. In one possible configuration, an inner radial surface of the support structure has a plurality of peripherally-spaced slots formed therein, and the stator winding comprises a plurality of stator coils, each of which is disposed in two non-adjacent, peripherally-spaced slots. Each of the slots is flanked by a pair of teeth which extends radially inwardly from the inner radial surface of the support structure and would aid in circumferentially locating the stator coils. A portion of each of the teeth may, if desired, be formed from a ferrous metal which would have the benefit of increasing flux linkage.
Another object of the invention is to provide a SER device which meets the first principal object and the stator of which is more-efficiently cooled than a standard air-cooled stator.
In accordance with another aspect of the invention, this object is achieved by using a liquid-cooled winding as the stator winding. The stator winding may, for instance, be formed from wire turns and have internal cooling tubes extending at least generally in parallel with the individual turns of the wire.
A second principal object of the invention is to provide an improved method of mounting a one-layer stator winding onto an associated support structure of a stator of an SER device so as to negate the need for any hangers, tape, rope, or other mechanical fasteners.
In accordance with another aspect of the invention, this object is achieved by potting each stator coil of the stator winding to two non-adjacent, peripherally-spaced locations on the support structure and potting the stator coils to one another.
Various potting options are available. For instance, the stator winding may be potted to the support structure via a one-step process that comprises 1) inserting an absorbent material such as felt into gaps in the stator winding and between adjacent stator coil sections and in gaps between the stator winding and the support structure, 2) depositing a resin into the stator so that the absorbent material absorbs resin and so that resin flows into other gaps not occupied by the absorbent material, and then 3) curing the resin. Alternatively, the stator winding may be potted to the support using a two-
Dombrovski Viatcheslav V.
Driscoll David I.
Shovkhet Boris A.
Horn John J.
Jaskolski Michael A.
Reliance Electric Technologies LLC
Waks Joseph
Walbrun William R.
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