Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K55/00—Dynamo-electric machines having windings operating at cryogenic temperatures
  • H02K55/02—Dynamo-electric machines having windings operating at cryogenic temperatures of the synchronous type
  • H02K55/04—Dynamo-electric machines having windings operating at cryogenic temperatures of the synchronous type with rotating field windings
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K2203/00—Specific aspects not provided for in the other groups of this subclass relating to the windings
  • H02K2203/15—Machines characterised by cable windings, e.g. high-voltage cables, ribbon cables
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
  • H02K3/12—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors arranged in slots
  • H02K3/14—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors arranged in slots with transposed conductors, e.g. twisted conductors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
  • H02K3/22—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors consisting of hollow conductors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
  • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

Definitions

• This invention relates to turbomachinery and, more particularly, to stator armature windings for an electrical machine using superconductive materials.
• the armature winding is located in stator slots, and steel teeth guide the main magnetic flux from the airgap to the stator yoke.
• the armature conductors are not exposed to the main magnetic flux but only to the significantly smaller slot leakage flux.
• the magnetic torque acts on the stator teeth that transfer it to the core and the stator frame.
• the small slot leakage field causes eddy current losses in the conductors of the armature winding and gives rise to forces acting on the slot-embedded conductors, which are manageable with present slot-support methods.
• the rotor field winding of a synchronous generator carries DC current and is exposed only to the relatively low magnetic leakage field. Therefore, the field winding has been traditionally the first focus for applying SC technology to generators.
• the field winding is assembled from superconductors to eliminate excitation I2R losses and to provide a source for magnetic airgap fields that are, in all concepts for SC generators presented to date, considerably higher than in conventional generators.
• the winding is cooled by liquid helium in the case of low temperature superconductors (LTSC) and liquid nitrogen in the case of a HTSC. Time- varying fields during load imbalance or transients such as during load shedding are shielded from the SC rotor winding by an electrically conductive shield around the rotor.
• the airgap armature winding is typically assembled from copper conductors that are supported by a nonmagnetic structure. These concepts have several inherent problems. The armature winding is exposed to the full airgap flux densities resulting in large AC losses in the copper conductors. Since the armature is located in the main airgap field, the full rated magnetic torque is acting directly on the armature winding, and radial forces are also significantly larger than in conventional generators. This requires that the nonmagnetic supporting structure of the armature winding be designed for both rated torque and large radial forces.
• SC wires have been implemented in AC power cable prototypes by various cable manufacturers.
• the electrical line-ground insulation is either at room temperature (warm dielectric) or cryogenic temperatures (cold dielectric), and the conductor is assembled from HTSC wire.
• the conductors in these AC power cables are exposed only to the small self-field, which is sufficiently small for today's superconducting materials.
• stator teeth serve to shield the SC winding from magnetic AC fields resulting in minimization of AC losses, forces and torques acting on the supeconducting wires. It would also be beneficial to manufacture the winding from continuous cables of superconducting wires or alternatively from multi-filamentary wires of aspect ratios close to unity. It may further be beneficial to employ magnetic wedges to further shield the SC conductors from AC magnetic fields.
• a superconducting synchronous generator in an exemplary embodiment of the invention, includes a rotor and a stator.
• the stator comprises a plurality of stator slots and armature windings respectively disposed in the stator slots.
• the armature windings are formed of superconductive cable.
• the superconductive cable may comprise multi-filamentary superconductive wire tape with an aspect ratio greater than one or alternatively with an aspect ratio of about one.
• the superconductive cable comprises continuous cables of superconducting wire.
• the superconductive cable may include a substantially concentrically layered construction including a cryo-refrigeration coolant passage, a superconductive material and insulation.
• the insulation may be thermal insulation disposed over electrical insulation or the opposite with electrical insulation disposed over thermal insulation.
• the stator may further include stator teeth defining the stator slots, where the stator teeth shield the superconductive cable from a majority of magnetic fields generated during operation of the generator.
• the armature windings of superconductive cable may be toroidal windings, and the stator may further include magnetic slot wedges respectively disposed in openings of the slots.
• an armature winding for an electrical machine is formed of superconductive cable.
• FIGURE 1 is a schematic illustration of a slot-embedded superconducting armature winding with a cold dielectric
• FIGURE 2 is a schematic illustration of a slot-embedded superconducting armature winding with a warm dielectric
• FIGURE 3 illustrates a toroidial slot-embedded SC armature winding for an example of a two-pole generator
• FIGURE 4 shows a slot-embedded superconducting cable made from superconducting tape of large aspect ratio
• FIGURE 5 shows slot-embedded superconducting cable made from superconducting tape of an aspect ratio close to unity
• FIGURE 6 shows a magnetic slot wedge disposed in the opening of the stator slot.
• an SC armature winding 10 is shown disposed in a conventional stator slot 12.
• the SC armature winding 10 is formed in a substantially concentric layered construction including a cryo-refrigeration coolant passage 14 for receiving coolant, a superconductor 16 and insulation 18, 20.
• the conductors 16 of the SC stator winding are placed in the stator slots 12 similar to the winding arrangement of conventional generators.
• the main magnetic flux is guided tlirough a toothed stator core 22 that shields the SC wire from large AC flux densities. Since the main magnetic field is guided through the laminated core structure, the magnetic forces, torques, and additional AC losses are limited to values that are due to only the slot leakage field, but not the main magnetic field.
• the forces and torques acting on the SC wires are comparable to the ones in conventional machines, and the SC conductors can be supported by conventional structures.
• SC wire is exposed to an AC field that is limited to the slot leakage field.
• the critical current density of the superconducting wire has to be reduced only modestly.
• the AC losses induced in the SC wire by the slot leakage field are minimal, and the full rated torque is transmitted to the magnetic yoke not by the armature winding, but rather by the magnetic teeth for better reliability.
• the superconductor may be arranged in several different configurations in the slot, either with a cold dielectric (thermal insulation 20 around the electrical insulation 18, as shown in FIGURE 1), or a warm dielectric (electrical insulation 18 around the thermal insulation 20, as shown in FIGURE 2), and the conductors may have either rectangular or round or other shaped configurations.
• the SC wires within a turn or coil will be arranged in accordance with any of the well-known techniques that reduce or eliminate circulating currents among the wires.
• One such technique uses the "Roebel" arrangement, for which longstanding patents by Ringland (Allis Chalmers) and Willyoung (General Electric) are typical.
• the wires will be wound in a spiral fashion to accomplish the cancellation of circulating currents
• the SC slot-embedded conductors may be connected in any of the typical connection schemes, such as individual bars or single- or multi-turn coils connected into a toroidal winding or a single- and multi-layer winding that is assembled from equal or concentric coils connected in a wave- or lap- winding pattern.
• the concept of SC slot embedded conductors also applies to salient pole stator windings and helical armature windings.
• a toroidal winding 23 consists of turns that extend around the yoke 24 of the stator core 22.
• the drawback of a toroidal winding in conventional generators is that they need approximately twice the coil length per induced voltage, resulting in twice the I2R losses of coils. This drawback of twice the I2R losses is eliminated by the use of SC wires as shown in FIGURE 3, and the advantage is compactness of the toroidal winding placed in a few slots/pole/phase.
• the slot-content of such a winding may implement the concepts of FIGURES 1 and 2.
• the cryogenic cooling paths 14 for the superconductor may be implemented in several configurations.
• each circuit of the armature winding forms a continuous cryogenic loop.
• each cryogenic circuit contains the same conductors as each electrical circuit.
• the cryogenic and electrical circuits may consist of different connection schemes.
• the cryogenic circuit may consist of a parallel connection of either individual coils or bars or groups of these.
• the superconducting armature winding is assembled from a continuous superconducting cable.
• the cable is assembled from layers of superconducting wire surrounded by a continuously extruded insulation system.
• the superconducting wire extends continuously between the two terminals of each phase, or sections thereof. This approach minimizes the splices of superconducting wire that are required compared to a winding assembled from individual bars or coils.
• the coolant may circulate either as an integral component of the continuous cable or around the extruded cable as part of the slot-containment of the cable. In the latter case, one or several cables can be immersed in the same coolant circuit within a slot.
• SC cable winding applies to all winding configurations and connection schemes, including single- and multi-layer windings, wave- and lap- windings, toroidal windings, salient-pole windings, helical windings.
• present prototypes of SC cables are built from multifilamentary SC wire tape with a high aspect ratio, i.e., a tape width that is several times the tape thickness.
• the conductor section 16 is preferably wound from such SC tape as indicated in FIGURE 4, where the individual tapes are twisted in the axial direction of the cable.
• the resulting self-field of the cable in air is indicated by the arrow A
• the self-field of slot-embedded cable is indicated by the arrow B.
• the magnetic leakage field A extends in peripheral direction of the cable and intersects the SC tape only over its thickness. Thereby, parasitic eddy currents are minimized.
• the magnetic leakage field B is perpendicular to the axis of the cable. If a conventional cable of FIGURE 4 is used, the magnetic leakage field would be perpendicular to the width of the SC wire tapes in a large section of the SC region. This would result in excessive eddy current losses that are proportional to the square of the tape dimension that is perpendicular to the magnetic field.
• a new configuration of wire tape is proposed, wherein the multi-filamentary SC wire has a cross section with an aspect ratio close to unity, such as wire strands of square or round cross sections as shown in FIGURE 5.
• magnetic slot wedges are employed to reduce the stator slotting permeances.
• magnetic slot wedges 26 are disposed in openings of the slots 12.
• the magnetic wedges 26 serve the additional purpose of shielding the SC wire embedded in the stator slot from airgap field harmonics due to rotor MMF and permeance harmonics.
• Anisotropic wedges may be employed to reduce the slot leakage field passing through the wedge by aligning the magnetic preferential direction of the anisotropic wedge with the radial direction of the slot. Magnetic flux lines are shown in FIGURE 6.
• a superconducting stator armature winding can be assembled into conventional stator slots.
• the stator teeth serve to shield the SC winding from magnetic AC fields, resulting in minimization of AC losses, forces and torques acting on the superconducting wires.
• the winding is manufactured from continuous cables of superconducting wires or alternatively from multi-filamentary wires of aspect ratios close to unity. Magnetic wedges further shield the SC conductors from AC magnetic fields.

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• 2001
  • 2001-12-12 MX MXPA02009646A patent/MXPA02009646A/es unknown
  • 2001-12-12 CA CA002403666A patent/CA2403666A1/en not_active Abandoned
  • 2001-12-12 CZ CZ20023126A patent/CZ20023126A3/cs unknown
  • 2001-12-12 WO PCT/US2001/048131 patent/WO2002063751A1/en not_active Application Discontinuation
  • 2001-12-12 CN CN01808792A patent/CN1426625A/zh active Pending
  • 2001-12-12 EP EP01994222A patent/EP1348251A1/de not_active Withdrawn
  • 2001-12-12 PL PL01364023A patent/PL364023A1/xx not_active Application Discontinuation

Non-Patent Citations (1)

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