CA2011732A1 - Axial gap superconducting electrical machine - Google Patents
Axial gap superconducting electrical machineInfo
- Publication number
- CA2011732A1 CA2011732A1 CA002011732A CA2011732A CA2011732A1 CA 2011732 A1 CA2011732 A1 CA 2011732A1 CA 002011732 A CA002011732 A CA 002011732A CA 2011732 A CA2011732 A CA 2011732A CA 2011732 A1 CA2011732 A1 CA 2011732A1
- Authority
- CA
- Canada
- Prior art keywords
- electrical machine
- armature
- coils
- shaft
- superconducting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
- H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices
- H02K29/08—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices using magnetic effect devices, e.g. Hall-plates, magneto-resistors
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Superconductive Dynamoelectric Machines (AREA)
- Brushless Motors (AREA)
Abstract
ABSTRACT
An axial gap superconducting electrical machine includes a housing, a shaft, bearing means in the housing for rotatably supporting the shaft, and at least one superconducting magnet assembly stationarily supported in the housing around the shaft. At least one armature assembly is mounted on the shaft in axially spaced alignment with the superconducting magnet assembly with the armature assembly including a plurality of coils mounted in slots in the assembly. The armature coils can be energized through slip rings on the shaft. The armature is made of non-magnetic material to reduce core loss. Yokes can be employed to confine magnetic flux, as needed, and in a single-ended stator design a back plate is used with the superconducting magnet assembly. The machine, in motor configuration, is fully adjustable in speed and torque and will provide full rated torque over the entire speed range.
An axial gap superconducting electrical machine includes a housing, a shaft, bearing means in the housing for rotatably supporting the shaft, and at least one superconducting magnet assembly stationarily supported in the housing around the shaft. At least one armature assembly is mounted on the shaft in axially spaced alignment with the superconducting magnet assembly with the armature assembly including a plurality of coils mounted in slots in the assembly. The armature coils can be energized through slip rings on the shaft. The armature is made of non-magnetic material to reduce core loss. Yokes can be employed to confine magnetic flux, as needed, and in a single-ended stator design a back plate is used with the superconducting magnet assembly. The machine, in motor configuration, is fully adjustable in speed and torque and will provide full rated torque over the entire speed range.
Description
7 ~ 2 . ~, .
IAL GAP SUPERCONDUCTING l~LECTRICAL IIACHINE -The U.S. Government has rights in the invention pursuant to U.S. Dept. of Energy Contract DE-AC05-840R21400 with Martin Marietta Energy Systems Inc. as operator of the Oak Ridge National Laboratory.
, :
Background of the Invention -~
, .
This invention relates generally to an electric machine, either motor or generator/alternator, and more ;
particularly the invention relates to a multiple-phase, electronically commutated and controlled, axial gap i electric machine using superconducting coils.
~I Superconducting windings have heretofore been pro-posed for use in electric motors and generators. With the exception of DC homopolar motors, little development has resulted for superconducting motors. However, the disco-t;~l ~, very of high-temperature 1-2-3 compound superconducting ;
material and the use of adjustable-speed drives make the use of superconducting coils in electric motors more feasible, both technically and economically.
Most known superconducting motor and generator i designs heretofore proposed have employed a radial gap ~i construction, and most designs have necessitated the transfer of superconducting fluid across a rotating ~; Attorney Docket No: EPRI-49665 HKW
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, interface. See, for example, U.S. Patent No. 4,267,473 3 for SUPERCONDUCTI~G GENERATOR THERMAL RADIATION SHIELD
-~ HAVING SUBSTANTIALLY UNIFORM TEMPERATURE, U.S. Patent No.
4,278,905 for APPARATUS FOR SUPPORTING STATOR WINDING IN
` ~ 5 SUPERCONDUCTIVE GENERATOR, and U.S. Patent No. 4,577,126 ~, for SYNCHRONOUS ELECTRIC MACHINE WITH SUPERCONDUCTIVE
FIELD WINDINGS. Further, considerable loss is experienced - in the magnetic material of the cores of such machines.
`:~ s ~j Axial gap motors are known; see for example U.S.
Patent No. 3,428,840 for AXIAL GAP GENERATOR WITH COOLING
ARRANGEMENT and U.S. Patent No. 4,072,881 for AXIAL
INTERGAP TYPE SEMICONDUCTOR ELECTRIC MOTOR. Halas, U.S.
Patent No. 3,521,901, proposed a stationary superconduct-ing magnet assembly with a normally-conducting armature located between a pair of magnet assemblies. The proposed Halas machine is single-speed and provides damping via the windings.
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-~, Summary of the Invention ~ 20 `~ An object of the present invention is a superconduct-l ing machine of modular design wherein a plurality of ;, stators and armatures can be stacked.
~, Another object of the invention is a superconducting ri~ 25 machine which is operated as a variable-speed motor and which is capable of delivering full rated torque over the full rated range of speed and load.
Another object of the invention is a superconducting , machine in which all magnetic material can be removed, thereby preventing high magnetic core losses.
~ Still another object of the invention is a motor or "sj generator having a stationary superconducting electromag-netic structure, thereby eliminating the requirement for ~`~` transferring a fluid refrigerant across a rotating interface.
.~i `~i,i Attorney Docket No: EPRI-49665 HKW
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:~ - 3 -Yet another object of the invention is a motor where commutated current is transmitted via slip rings or induc-. .
tive coupling from an adjustable-speed drive to the arma-~l tures.
;~ 5 A further object of the invention is a minimization `~ of distortion of electromagnetic flux by the armature cur-rent in a superconducting machine.
Another object of the invention is a motor or ~-, generator wherein the field is contained substantially , 10 within the motor volume, thereby reducing the amount of required shielding and allowing for active EM shielding, if required.
~; A feature of the invention is a multi-pole axial gap design including stationary superconducting electromagnets and armatures having low-current windings.
~- Briefly, a superconducting machine in accordance with i3 the invention includes at least one stationary supercon-~- ducting electromagnet assembly and at least one armature assembly having a plurality of low-current coils thereon.
The armature is made of a non-magnetic material having slots for accommodating the low-current-carrying coils.
~`~ The superconducting electromagnetic assembly and two armature assemblies form a module, and a plurality of modules appropriately positioned can be stacked in a motor ; 25 housing. There is no necessity for Amortisseur windings ,l for starting and damping; these functions are accomplished by an ad~ustable-speed drive (ASD). A speed-and-position encoder on the drive shaft provides relative position information to the ASD.
The stationary electromagnet assembly has coils of superconducting wire; this wire may consist of Niobium--i Tin, Niobium-Titanium, or be made of high-temperature superconducting (1-2-3) compounds such as YBa2Cu3O7. The ` coils and coolant are contained in nonmetallic composite housings.
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The composi~e housing, consisting of resin epoxy and carbon or glass fibers, retains the coolant and restrains enclosed superconducting windings against electromagnetic forces. In alternative embodiments, iron yokes and back ~l 5 plates can be employed to facilitate definition of the ~3 electromagnetic flux path.
~-~ The invention and objects and features thereof will be more readily apparent from the following detailed :~ .
description and appended claims when taken with the 10 drawings.
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Brief Description of the Drawing ; Fig. 1 is a perspective view, partially in section, ;~ of a stacked axial gap superconducting motor in accordance ~ 5 15 with one embodiment of the invention.
Fig. 2 is a perspective view of a stationary super-conducting magnet assembly and cooperative armature as-~ semblies of one module in the superconducting motor of r~l Fig. 1.
1- 20 Fig. 3 is a section view illustrating the configura-` tion of a superconducting coil and adjacent armatures in accordance with one embodiment of the invention.
Fig. 4 is a plan view of the stationary superconduct-ing magnet assembly of Fig. 2.
Fig. 5 is a section view through the superconducting magnet assembly of Fig. 4 taken along the line A-A in accordance with one embodiment of the invention.
} Fig. 6 is a section view of the superconducting mag-net assembly taken along the line A-A of Fig. 4 in ~i 30 accordance with another embodiment of the invention.
` Fig. 7 is a section view of the superconducting mag-net assembly of Fig. 4 taken along the line A-A in accordance with another embodiment of the invention.
Fig. 8 is a diagram of one embodiment of the armature 35 winding of the motor of Fig. 1.
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Attorney Docket No: EPRI-49665 HKW
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~1 Fig. 9 is a diagram of a wye connection of the arma--~ ture winding of Fig. 8.
Fig. 10 is a block diagram of an adjustable-speed i~ device for energizing the armature windings.
Fig. 11 is a schematic of the power circuitry for driving the armature windings.
`l ~-, Detailed Description of Illustrative Embodiments Referring now to the drawing, Fig. 1 is a perspective view, partially in section, of a superconducting motor in accordance with one embodiment of the invention. The ~ motor includes a housing 10 which is partially cut away to .~'l show the internal structure of the motor. A shaft 12 is '"! mounted on bearings 14 at either end of the housing, and , 15 mounted on shaft 12 are a plurality of armatures 16.
` Positioned between armatures 16 are stationary supercon-~, ducting magnet assemblies 18. The magnet assemblies are ;~ spaced from adjacent armatures by an axial air gap. A
magnet cooling system 20 provides a cryogenic fluid coolant to the stationary superconducting magnet assembly.
With the new high-temperature 1-2-3 superconducting compounds, such as YBa2Cu307, the coolant can be liquid nitrogen. In accordance with standard practice, DC power ~l for the superconducting magnets is provided by supply 22, and electrical power for the armature windings is provided by an adjustable-speed drive (ASD) voltage supply 24. In '`~ accordance with a feature of the invention, the provision `~ of voltage from the ASD to the armature windings is effected through slip rings (Fig. 2), or with inductive coupling, thereby obviating the need for commutator brushes in either case.
~, The superconductor motor has a modular design whereby ~¦ one or more stationary superconducting magnet assemblies can be stacked on a shaft along with one or more armature assemblies in a stacked modular arrangement. Accordingly, motor ratings can be readily shaped by the number of ~i Attorney Docket No: EPRI-49665 HKW
~'i SJO/HKW/EPRI/49665/CA
.:.''" ~'- ~- ' ~3 ~ .. , i. ' *' 7 i~, , modular assemblies employed. The embodiment of Fig.
~` employs two stators and four armatures with four ~uper-cooled magnet coils per stator. An important feature of this configuration is the full utilization of the flux of ~: 5 the coils on both coil sides as will be described further ~1, hereinbelow.
~:j Fig. 2 is a perspective view of one module of the ~.'3 motor of Fig. 1 with the armature assembly 16 and the !- ~ superconducting magnet assembly 18 being exploded apart ~3j 10 to further illustrate the superconducting coils in the ' magnet assembly 18. In this embodiment, four toroidal ' ~3 superconducting coils are employed. Fig. 3 is a 3 section view through a coil and adjacent portions of the -~i armatures illustrating the configuration and dimensions of the coil with respect to the adjacent armature assemblies.
This is a design for a motor with four poles and 48 slots.
The windings are full pitch with 6 turns per coil and two ~ coil sides in each armature slot. The coil current is 16 -, amperes (300 A/cm2) and the four slots/pole/phase are ~ 20 considered in series, as will be described more fully i~ herein with reference to the winding diagram of Fig. 8.
,~ However, it will be appreciated that this is one embodi-ment of many possible armature winding patterns and stator pole patterns. No Amortisseur windings are required as the motor is considered to be driven by an adjustable-fre-quency drive. The magnet and armature configuration are ~ sized to produce the desired air gap flux density without ;~; distortion from the flux produced by the armature ;~ currents. Energization of the armature coils is effected through slip rings 20.
` Each coil has a diameter of nine inches with a cross-section being three inches square. The armature slots are 0.375 inch wide. The slots are 0.75 inch in depth and the i~', electromagnetic air gap between the stator and armature is approximately one inch. The armature structure is made of a non-magnetic material such as TorlonTM OR STYCASTTM.
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Attorney Docket No: EPRI-49665 HKW
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-~ Fig. 4 is a plan view of the stationary superconduct-~! ing maqnet assembly of the axial gap superconducting -~ motor, and Figs. 5-7 are section views taken along the line A-A in Fig. 4 which illustrate different embodiments of the motor assembly.
In Fig. 5, two armatures 30 made of non-magnetic ~` material are shown separated by air gap 32 from two ferromagnetic yokes 34 with the nonmagnetic armatures 30 `~ incrementally divided by slots 36. The ferromagnetic `l lO yokes 34 close the flux path from the double-ended ~5 supercooled electromagnet 28. In principle, the ferromag-;~ netic material may comprise the outer housing of the .. `J, machine.
In the embodiment of Fig. 6, a single-ended super-,i 15 cooled electromagnet 28 has a back plate 40 which is ~` utilized to confine the magnetic flux. The armature 30 is separated by air gap 32 from yoke 34. In both the configurations of Fig. 5 and Fig. 6, the yokes 34 must remain stationary, along with the back plate 40 of Fig. 6, to prevent high core losses in the magnetic material ~'~' induced by the high fields of the supercooled magnets. In both Fig. 5 and Fig. 6, each of the slots 36 has two distributed winding coil sides therein.
Referring to Fig. 7, the current flow through the electromagnet 28 is illustrated as entering the supercon-ducting magnet side 28 at point 42 and leaving the super-conducting magnet side 28' at point 44. A resin/epoxy composite housing 46 retains cryogenic (for example, liquid nitrogen, Helium, or oxygen as required) coolant and restrains the enclosed superconductor wires against electromagnetic forces. This embodiment is an "ironless"
~` configuration, requiring neither iron core in the electromagnet nor iron yokes. The advantage of the "ironless" configuration is that higher magnetic fields -- 35 than used in prior-art machines may be employed; there is ~- not iron (magnetic material) to saturate, ~hereby heating ~,:
Attorney Docket No: EPRI-49665 HKN
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the machine. A composite housing 48 contains the entire motor assembly. In an illustrative embodiment, the following armature and stator slot loading is employed:
SC Electromagnet (Stator) Basic Range Turns 880 vary Current, Amps 920 vary Jop (A/CM2) 14,000 2-20 thousand Airgap flux density (Tesla) 3.5 2-7 ~ Armature Slots ,~ Basic Range ,} 15 Turns 12 vary Current, Amps 16 vary Jop (A/CM2) 200 100-400 ?1 -: ~
;-, 20 Fig. 8 is a schematic of one embodiment of the `i armature winding of the motor of Fig. 1. The armature j winding is a three-phase, double-layer, full-pitch, sinusoidally distributed configuration. The winding diagram shows only one phase of a four-pole, 48-slot armature. There are four slots/pole/phase and thus the figure shows 16 slots occupied by coil sides. The first coil has one side in the top of slot 1 and one side in the bottom of slot 13. The second coil has one side in the top of slot 2 and the other side in the bottom of slot 14.
The other two coils follow the same pattern. Instan-taneous current enters the coil sides in slot 1 and exits the coil side in slot 13. The embodiment of the figure ~-~shows the four coils in series. The instantaneous current exiting the bottom coil side in slot 13 enters the top 35 coil side in slot 2, and this pattern is repeated. These four series coils have two connections labelled l+ and 1-.
j The other coils are arranged in a like manner and are connected 2+ and 2-, 3+ and 3-, and 4+ and 4-. These connections are then arranged as one leg of a three-phase WYE as shown in Fig. 9.
Attorney Docket No: EPRI-49665 HKW
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_ 9 _ A block diagram of one illustrative embodiment of a motor control system is shown in Fig. 10. The drive package power section consists of a pair of switching regulators and output inverters. The power section schematic is shown in Fig. 11. Each switching regulator operates at lKHz with a variable pulse width, thereby controlling the voltage applied to the associated inverter. Each inverter produces a six-step output waveform that is phase-locked to the motor via a Hall probe signal and control circuitry. The inverter ouputs are tied in parallel to the armature and are capable of delivering 50KW. All control signals between the power section and controller are isolated by optical fibers or magnetic circuits.
The controller, built around a Motorola 68701 or similar microprocessor, maintains optimum armature field phasing, controlled motor current, performs numerous self-checks, and responds, as necessary, to power-section faults. It also provides for self-starting and damping control of the motor.
A single Hall probe, mounted on one armature, developes a stator-position reference signal which is phase-shifted by a programmable counter. Hall probe leads are attached to slip rings on the armature and the signals are transmitted to and from the ASD via the slip ring system. In another embodiment, a magnetic encoder mounted off of the main motor drive shaft will provide armature position information, thereby eliminating these slip rings and the Hall probe. Phase-locked loop circuitry multiplies the shifted reference, and combinational logic -~
provides the six-step waveforms necessary to control the power inverter. Optimum phase angle, based on motor speed and current, is continually maintained, thereby I maximizing motor efficiency.
- 35 A second programmable counter is used to develop a variable-pulse-width, fixed-frequency switching regulator Attorney Docket No: EPRI-49665 HKW
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control signal. This yields direct motor-current control with sufficient resolution to achieve speed regulation ~reater than 0.002% over the full range of motor loads.
Once at speed, a value of motor torque angle can be set by manually changing the magnitude of the millivolt input to the analog-to-digital converter.
The described superconducting machine can be utilized in both low- (30) horsepower and high- (3000) horsepower applications. The low-horsepower motors will have appli-cations in all electric vehicle motors, compressor motorsfor withdrawal compressors, refrigeration plant motors, and space-based motors for use in space stations and tethered satellites. The high-horsepower motors will I have applicability in gaseous diffusion plant compressor ¦ 15 motors and in waste-water-treatment plant motors, for example. Other examples of expected applications include feed water pumps, fan drives, train motors, generators (aerospace, power plant) and marine propulsion motors.
There has been described a variable-speed, axial gap electric machine featuring a superconductor stator I centered between two armatures. The motor eliminates the need for liquid refrigerant transfer across a rotating interface, balance problems associated with rotating , liquids, and high-current brushes associated with previous superconducting motor/generator designs. Analysis has shown that the axial gap design presents an extremely uniform total magnetic field to the armature coils, and the design can allow for elimination of all iron and provide increased power density with the "air core"
design. The axial gap design allows for use of both sides of the electromagnet and is amenable to stacking multiple sets of rotors and stators on a common drive shaft. The configuration is mechanically easier to modify - than radial gap motors.
While the invention has been de~cribed with reference to specific embodiments, the description is illustrative - Attorney Docket No: EPRI-49665 HKW
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of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
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IAL GAP SUPERCONDUCTING l~LECTRICAL IIACHINE -The U.S. Government has rights in the invention pursuant to U.S. Dept. of Energy Contract DE-AC05-840R21400 with Martin Marietta Energy Systems Inc. as operator of the Oak Ridge National Laboratory.
, :
Background of the Invention -~
, .
This invention relates generally to an electric machine, either motor or generator/alternator, and more ;
particularly the invention relates to a multiple-phase, electronically commutated and controlled, axial gap i electric machine using superconducting coils.
~I Superconducting windings have heretofore been pro-posed for use in electric motors and generators. With the exception of DC homopolar motors, little development has resulted for superconducting motors. However, the disco-t;~l ~, very of high-temperature 1-2-3 compound superconducting ;
material and the use of adjustable-speed drives make the use of superconducting coils in electric motors more feasible, both technically and economically.
Most known superconducting motor and generator i designs heretofore proposed have employed a radial gap ~i construction, and most designs have necessitated the transfer of superconducting fluid across a rotating ~; Attorney Docket No: EPRI-49665 HKW
~ .
~ ~ ~L .i.
. ~ -- 2 --.. ~
, interface. See, for example, U.S. Patent No. 4,267,473 3 for SUPERCONDUCTI~G GENERATOR THERMAL RADIATION SHIELD
-~ HAVING SUBSTANTIALLY UNIFORM TEMPERATURE, U.S. Patent No.
4,278,905 for APPARATUS FOR SUPPORTING STATOR WINDING IN
` ~ 5 SUPERCONDUCTIVE GENERATOR, and U.S. Patent No. 4,577,126 ~, for SYNCHRONOUS ELECTRIC MACHINE WITH SUPERCONDUCTIVE
FIELD WINDINGS. Further, considerable loss is experienced - in the magnetic material of the cores of such machines.
`:~ s ~j Axial gap motors are known; see for example U.S.
Patent No. 3,428,840 for AXIAL GAP GENERATOR WITH COOLING
ARRANGEMENT and U.S. Patent No. 4,072,881 for AXIAL
INTERGAP TYPE SEMICONDUCTOR ELECTRIC MOTOR. Halas, U.S.
Patent No. 3,521,901, proposed a stationary superconduct-ing magnet assembly with a normally-conducting armature located between a pair of magnet assemblies. The proposed Halas machine is single-speed and provides damping via the windings.
: j , . .
-~, Summary of the Invention ~ 20 `~ An object of the present invention is a superconduct-l ing machine of modular design wherein a plurality of ;, stators and armatures can be stacked.
~, Another object of the invention is a superconducting ri~ 25 machine which is operated as a variable-speed motor and which is capable of delivering full rated torque over the full rated range of speed and load.
Another object of the invention is a superconducting , machine in which all magnetic material can be removed, thereby preventing high magnetic core losses.
~ Still another object of the invention is a motor or "sj generator having a stationary superconducting electromag-netic structure, thereby eliminating the requirement for ~`~` transferring a fluid refrigerant across a rotating interface.
.~i `~i,i Attorney Docket No: EPRI-49665 HKW
~,- SJO/HKW/EPRI/49665/CA
. ~ . .
,,, :: 7 . ~ :
:~ - 3 -Yet another object of the invention is a motor where commutated current is transmitted via slip rings or induc-. .
tive coupling from an adjustable-speed drive to the arma-~l tures.
;~ 5 A further object of the invention is a minimization `~ of distortion of electromagnetic flux by the armature cur-rent in a superconducting machine.
Another object of the invention is a motor or ~-, generator wherein the field is contained substantially , 10 within the motor volume, thereby reducing the amount of required shielding and allowing for active EM shielding, if required.
~; A feature of the invention is a multi-pole axial gap design including stationary superconducting electromagnets and armatures having low-current windings.
~- Briefly, a superconducting machine in accordance with i3 the invention includes at least one stationary supercon-~- ducting electromagnet assembly and at least one armature assembly having a plurality of low-current coils thereon.
The armature is made of a non-magnetic material having slots for accommodating the low-current-carrying coils.
~`~ The superconducting electromagnetic assembly and two armature assemblies form a module, and a plurality of modules appropriately positioned can be stacked in a motor ; 25 housing. There is no necessity for Amortisseur windings ,l for starting and damping; these functions are accomplished by an ad~ustable-speed drive (ASD). A speed-and-position encoder on the drive shaft provides relative position information to the ASD.
The stationary electromagnet assembly has coils of superconducting wire; this wire may consist of Niobium--i Tin, Niobium-Titanium, or be made of high-temperature superconducting (1-2-3) compounds such as YBa2Cu3O7. The ` coils and coolant are contained in nonmetallic composite housings.
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Attorney Docket No: EPRI-49665 HKW
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The composi~e housing, consisting of resin epoxy and carbon or glass fibers, retains the coolant and restrains enclosed superconducting windings against electromagnetic forces. In alternative embodiments, iron yokes and back ~l 5 plates can be employed to facilitate definition of the ~3 electromagnetic flux path.
~-~ The invention and objects and features thereof will be more readily apparent from the following detailed :~ .
description and appended claims when taken with the 10 drawings.
J
Brief Description of the Drawing ; Fig. 1 is a perspective view, partially in section, ;~ of a stacked axial gap superconducting motor in accordance ~ 5 15 with one embodiment of the invention.
Fig. 2 is a perspective view of a stationary super-conducting magnet assembly and cooperative armature as-~ semblies of one module in the superconducting motor of r~l Fig. 1.
1- 20 Fig. 3 is a section view illustrating the configura-` tion of a superconducting coil and adjacent armatures in accordance with one embodiment of the invention.
Fig. 4 is a plan view of the stationary superconduct-ing magnet assembly of Fig. 2.
Fig. 5 is a section view through the superconducting magnet assembly of Fig. 4 taken along the line A-A in accordance with one embodiment of the invention.
} Fig. 6 is a section view of the superconducting mag-net assembly taken along the line A-A of Fig. 4 in ~i 30 accordance with another embodiment of the invention.
` Fig. 7 is a section view of the superconducting mag-net assembly of Fig. 4 taken along the line A-A in accordance with another embodiment of the invention.
Fig. 8 is a diagram of one embodiment of the armature 35 winding of the motor of Fig. 1.
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Attorney Docket No: EPRI-49665 HKW
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~1 Fig. 9 is a diagram of a wye connection of the arma--~ ture winding of Fig. 8.
Fig. 10 is a block diagram of an adjustable-speed i~ device for energizing the armature windings.
Fig. 11 is a schematic of the power circuitry for driving the armature windings.
`l ~-, Detailed Description of Illustrative Embodiments Referring now to the drawing, Fig. 1 is a perspective view, partially in section, of a superconducting motor in accordance with one embodiment of the invention. The ~ motor includes a housing 10 which is partially cut away to .~'l show the internal structure of the motor. A shaft 12 is '"! mounted on bearings 14 at either end of the housing, and , 15 mounted on shaft 12 are a plurality of armatures 16.
` Positioned between armatures 16 are stationary supercon-~, ducting magnet assemblies 18. The magnet assemblies are ;~ spaced from adjacent armatures by an axial air gap. A
magnet cooling system 20 provides a cryogenic fluid coolant to the stationary superconducting magnet assembly.
With the new high-temperature 1-2-3 superconducting compounds, such as YBa2Cu307, the coolant can be liquid nitrogen. In accordance with standard practice, DC power ~l for the superconducting magnets is provided by supply 22, and electrical power for the armature windings is provided by an adjustable-speed drive (ASD) voltage supply 24. In '`~ accordance with a feature of the invention, the provision `~ of voltage from the ASD to the armature windings is effected through slip rings (Fig. 2), or with inductive coupling, thereby obviating the need for commutator brushes in either case.
~, The superconductor motor has a modular design whereby ~¦ one or more stationary superconducting magnet assemblies can be stacked on a shaft along with one or more armature assemblies in a stacked modular arrangement. Accordingly, motor ratings can be readily shaped by the number of ~i Attorney Docket No: EPRI-49665 HKW
~'i SJO/HKW/EPRI/49665/CA
.:.''" ~'- ~- ' ~3 ~ .. , i. ' *' 7 i~, , modular assemblies employed. The embodiment of Fig.
~` employs two stators and four armatures with four ~uper-cooled magnet coils per stator. An important feature of this configuration is the full utilization of the flux of ~: 5 the coils on both coil sides as will be described further ~1, hereinbelow.
~:j Fig. 2 is a perspective view of one module of the ~.'3 motor of Fig. 1 with the armature assembly 16 and the !- ~ superconducting magnet assembly 18 being exploded apart ~3j 10 to further illustrate the superconducting coils in the ' magnet assembly 18. In this embodiment, four toroidal ' ~3 superconducting coils are employed. Fig. 3 is a 3 section view through a coil and adjacent portions of the -~i armatures illustrating the configuration and dimensions of the coil with respect to the adjacent armature assemblies.
This is a design for a motor with four poles and 48 slots.
The windings are full pitch with 6 turns per coil and two ~ coil sides in each armature slot. The coil current is 16 -, amperes (300 A/cm2) and the four slots/pole/phase are ~ 20 considered in series, as will be described more fully i~ herein with reference to the winding diagram of Fig. 8.
,~ However, it will be appreciated that this is one embodi-ment of many possible armature winding patterns and stator pole patterns. No Amortisseur windings are required as the motor is considered to be driven by an adjustable-fre-quency drive. The magnet and armature configuration are ~ sized to produce the desired air gap flux density without ;~; distortion from the flux produced by the armature ;~ currents. Energization of the armature coils is effected through slip rings 20.
` Each coil has a diameter of nine inches with a cross-section being three inches square. The armature slots are 0.375 inch wide. The slots are 0.75 inch in depth and the i~', electromagnetic air gap between the stator and armature is approximately one inch. The armature structure is made of a non-magnetic material such as TorlonTM OR STYCASTTM.
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Attorney Docket No: EPRI-49665 HKW
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-~ Fig. 4 is a plan view of the stationary superconduct-~! ing maqnet assembly of the axial gap superconducting -~ motor, and Figs. 5-7 are section views taken along the line A-A in Fig. 4 which illustrate different embodiments of the motor assembly.
In Fig. 5, two armatures 30 made of non-magnetic ~` material are shown separated by air gap 32 from two ferromagnetic yokes 34 with the nonmagnetic armatures 30 `~ incrementally divided by slots 36. The ferromagnetic `l lO yokes 34 close the flux path from the double-ended ~5 supercooled electromagnet 28. In principle, the ferromag-;~ netic material may comprise the outer housing of the .. `J, machine.
In the embodiment of Fig. 6, a single-ended super-,i 15 cooled electromagnet 28 has a back plate 40 which is ~` utilized to confine the magnetic flux. The armature 30 is separated by air gap 32 from yoke 34. In both the configurations of Fig. 5 and Fig. 6, the yokes 34 must remain stationary, along with the back plate 40 of Fig. 6, to prevent high core losses in the magnetic material ~'~' induced by the high fields of the supercooled magnets. In both Fig. 5 and Fig. 6, each of the slots 36 has two distributed winding coil sides therein.
Referring to Fig. 7, the current flow through the electromagnet 28 is illustrated as entering the supercon-ducting magnet side 28 at point 42 and leaving the super-conducting magnet side 28' at point 44. A resin/epoxy composite housing 46 retains cryogenic (for example, liquid nitrogen, Helium, or oxygen as required) coolant and restrains the enclosed superconductor wires against electromagnetic forces. This embodiment is an "ironless"
~` configuration, requiring neither iron core in the electromagnet nor iron yokes. The advantage of the "ironless" configuration is that higher magnetic fields -- 35 than used in prior-art machines may be employed; there is ~- not iron (magnetic material) to saturate, ~hereby heating ~,:
Attorney Docket No: EPRI-49665 HKN
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the machine. A composite housing 48 contains the entire motor assembly. In an illustrative embodiment, the following armature and stator slot loading is employed:
SC Electromagnet (Stator) Basic Range Turns 880 vary Current, Amps 920 vary Jop (A/CM2) 14,000 2-20 thousand Airgap flux density (Tesla) 3.5 2-7 ~ Armature Slots ,~ Basic Range ,} 15 Turns 12 vary Current, Amps 16 vary Jop (A/CM2) 200 100-400 ?1 -: ~
;-, 20 Fig. 8 is a schematic of one embodiment of the `i armature winding of the motor of Fig. 1. The armature j winding is a three-phase, double-layer, full-pitch, sinusoidally distributed configuration. The winding diagram shows only one phase of a four-pole, 48-slot armature. There are four slots/pole/phase and thus the figure shows 16 slots occupied by coil sides. The first coil has one side in the top of slot 1 and one side in the bottom of slot 13. The second coil has one side in the top of slot 2 and the other side in the bottom of slot 14.
The other two coils follow the same pattern. Instan-taneous current enters the coil sides in slot 1 and exits the coil side in slot 13. The embodiment of the figure ~-~shows the four coils in series. The instantaneous current exiting the bottom coil side in slot 13 enters the top 35 coil side in slot 2, and this pattern is repeated. These four series coils have two connections labelled l+ and 1-.
j The other coils are arranged in a like manner and are connected 2+ and 2-, 3+ and 3-, and 4+ and 4-. These connections are then arranged as one leg of a three-phase WYE as shown in Fig. 9.
Attorney Docket No: EPRI-49665 HKW
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_ 9 _ A block diagram of one illustrative embodiment of a motor control system is shown in Fig. 10. The drive package power section consists of a pair of switching regulators and output inverters. The power section schematic is shown in Fig. 11. Each switching regulator operates at lKHz with a variable pulse width, thereby controlling the voltage applied to the associated inverter. Each inverter produces a six-step output waveform that is phase-locked to the motor via a Hall probe signal and control circuitry. The inverter ouputs are tied in parallel to the armature and are capable of delivering 50KW. All control signals between the power section and controller are isolated by optical fibers or magnetic circuits.
The controller, built around a Motorola 68701 or similar microprocessor, maintains optimum armature field phasing, controlled motor current, performs numerous self-checks, and responds, as necessary, to power-section faults. It also provides for self-starting and damping control of the motor.
A single Hall probe, mounted on one armature, developes a stator-position reference signal which is phase-shifted by a programmable counter. Hall probe leads are attached to slip rings on the armature and the signals are transmitted to and from the ASD via the slip ring system. In another embodiment, a magnetic encoder mounted off of the main motor drive shaft will provide armature position information, thereby eliminating these slip rings and the Hall probe. Phase-locked loop circuitry multiplies the shifted reference, and combinational logic -~
provides the six-step waveforms necessary to control the power inverter. Optimum phase angle, based on motor speed and current, is continually maintained, thereby I maximizing motor efficiency.
- 35 A second programmable counter is used to develop a variable-pulse-width, fixed-frequency switching regulator Attorney Docket No: EPRI-49665 HKW
:
. :.
control signal. This yields direct motor-current control with sufficient resolution to achieve speed regulation ~reater than 0.002% over the full range of motor loads.
Once at speed, a value of motor torque angle can be set by manually changing the magnitude of the millivolt input to the analog-to-digital converter.
The described superconducting machine can be utilized in both low- (30) horsepower and high- (3000) horsepower applications. The low-horsepower motors will have appli-cations in all electric vehicle motors, compressor motorsfor withdrawal compressors, refrigeration plant motors, and space-based motors for use in space stations and tethered satellites. The high-horsepower motors will I have applicability in gaseous diffusion plant compressor ¦ 15 motors and in waste-water-treatment plant motors, for example. Other examples of expected applications include feed water pumps, fan drives, train motors, generators (aerospace, power plant) and marine propulsion motors.
There has been described a variable-speed, axial gap electric machine featuring a superconductor stator I centered between two armatures. The motor eliminates the need for liquid refrigerant transfer across a rotating interface, balance problems associated with rotating , liquids, and high-current brushes associated with previous superconducting motor/generator designs. Analysis has shown that the axial gap design presents an extremely uniform total magnetic field to the armature coils, and the design can allow for elimination of all iron and provide increased power density with the "air core"
design. The axial gap design allows for use of both sides of the electromagnet and is amenable to stacking multiple sets of rotors and stators on a common drive shaft. The configuration is mechanically easier to modify - than radial gap motors.
While the invention has been de~cribed with reference to specific embodiments, the description is illustrative - Attorney Docket No: EPRI-49665 HKW
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of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
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~;~, Attorney Docket No: EPRI-49665 HKW
~- SJO/HKW/EPRI/49665/CA
Claims (15)
1. A superconducting electrical machine comprising a housing, a shaft, bearing means in said housing for rotatably support-ing said shaft, at least one superconducting magnet assembly stationarily supported in said housing around said shaft, at least one armature assembly mounted on said shaft in axially spaced alignment with said superconducting magnet assembly, said armature assembly including a plurality of coils, and means for energizing said coils including an adjustable-speed drive (ASD).
2. The superconductor electrical machine as defined by claim 1 wherein said superconducting magnet assembly includes a plurality of coils of superconducting material and means for containing said coils in a coolant.
3. The superconductor electrical machine as defined by claim 2 wherein said superconducting magnet assembly includes 2N superconducting coils axially aligned in parallel with said shaft and providing magnetic flux through said plurality of coils, when N is an integer.
4. The superconductor electrical machine as defined by claim 3 wherein said superconducting magnet assembly includes four superconducting coils axially aligned in parallel with said shaft and providing magnetic flux through said plurality of coils.
5. The superconductor electrical machine as defined by claim 2 wherein said armature assembly includes a plurality of slots for supporting said plurality of coils in close proximity to said superconducting magnet assembly.
6. The superconductor electrical machine as defined by claim 5 and including a plurality of superconducting magnet assemblies, each superconducting magnet assembly being positioned between two armature assemblies.
7. The superconductor electrical machine as defined by claim 6 wherein said two armature assemblies and a superconducting magnet assembly therebetween comprise a module.
8. The superconductor electrical machine as defined by claim 7 wherein said electrical machine comprises a plurality of modules.
9. The superconductor electrical machine as defined by claim 1 wherein said electrical machine includes two armature assemblies and further including yoke means associated with each armature assembly for further confin-ing magnetic flux.
10. The superconductor electrical machine as defined by claim 1 wherein said electrical machine includes a single superconducting magnet assembly including a ferro-magnetic back plate.
11. The superconductor electrical machine as defined by claim 1 wherein said means for energizing said coils includes slip rings on said shaft.
12. The superconductor electrical machine as defined by claim 1 wherein said means for energizing said coils includes inductive coupling of driving voltage.
13. The superconductor electrical machine as defined by claim 1 wherein said armature assembly comprises non-magnetic material.
14. The superconductor electrical machine as defined by claim 1 and further including a Hall probe mounted on said armature for providing armature position information to said adjustable-speed drive.
15. The superconductor electrical machine as defined by claim 1 and further including a magnetic encoder mounted on said shaft for providing armature position information.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32858089A | 1989-03-27 | 1989-03-27 | |
| US328,580 | 1989-03-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2011732A1 true CA2011732A1 (en) | 1990-09-27 |
Family
ID=23281563
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002011732A Abandoned CA2011732A1 (en) | 1989-03-27 | 1990-03-08 | Axial gap superconducting electrical machine |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH03117359A (en) |
| CA (1) | CA2011732A1 (en) |
| DE (1) | DE4008912A1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4036699A1 (en) * | 1990-05-11 | 1991-11-21 | Hubert Mauel | Superconducting motor with electromagnets in four quadrant chambers - mfd. of plastic and filled with cryogenic liq. for cooling of ceramic-dust-filled windings |
| US6597082B1 (en) | 2000-08-04 | 2003-07-22 | American Superconductor Corporation | HTS superconducting rotating machine |
| ATE306139T1 (en) * | 2000-01-11 | 2005-10-15 | American Superconductor Corp | SUPERCONDUCTING ROTATING ELECTRICAL MACHINE WITH HIGH-TEMPERATURE SUPERCONDUCTORS |
| KR20020091529A (en) * | 2001-05-31 | 2002-12-06 | 대한민국(관리부서:산업자원부 기술표준원장) | Superconducting power supply of a rotating magnetic flux type |
| GB2417140B (en) * | 2004-08-09 | 2008-01-23 | Alstom | Rotating superconducting machines |
| JP2006204085A (en) | 2004-12-24 | 2006-08-03 | Sumitomo Electric Ind Ltd | Axial gap type superconducting motor |
| US8847464B2 (en) * | 2008-06-12 | 2014-09-30 | General Electric Company | Electrical machine with improved stator flux pattern across a rotor that permits higher torque density |
| ITMI20112386A1 (en) * | 2011-12-27 | 2013-06-28 | Phase Motion Control S P A | "SYNCHRONOUS GENERATOR MOTOR TO SUPERCONDUCTORS" |
| CN102594220B (en) * | 2012-01-21 | 2015-08-19 | 哈尔滨工业大学 | Magnetic suspension planar motor with superconductor excitation structure |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3428840A (en) * | 1967-01-09 | 1969-02-18 | Garrett Corp | Axial air gap generator with cooling arrangement |
| DE1613005B2 (en) * | 1967-03-18 | 1971-09-02 | Gebr Buhler Nachfolger GmbH, 8500 Nürnberg | COLLECTORLESS DC MOTOR |
| US3521901A (en) * | 1968-08-14 | 1970-07-28 | Mitchell A Wackym | Shoulder belt comfort strap |
| US4072881A (en) * | 1975-11-06 | 1978-02-07 | Itsuki Ban | Axial-air-gap type semiconductor electric motor |
| US4267473A (en) * | 1976-11-23 | 1981-05-12 | Electric Power Research Institute | Superconducting generator thermal radiation shield having substantially uniform temperature |
| US4278905A (en) * | 1977-12-27 | 1981-07-14 | Electric Power Research Institute | Apparatus for supporting a stator winding in a superconductive generator |
| FR2514965B1 (en) * | 1981-10-19 | 1985-11-29 | Lorraine Inst Nat Polytech | SYNCHRONOUS ELECTRICAL MACHINE WITH SUPERCONDUCTIVE INDUCTOR |
-
1990
- 1990-03-08 CA CA002011732A patent/CA2011732A1/en not_active Abandoned
- 1990-03-20 DE DE4008912A patent/DE4008912A1/en not_active Ceased
- 1990-03-27 JP JP2078604A patent/JPH03117359A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03117359A (en) | 1991-05-20 |
| DE4008912A1 (en) | 1990-10-04 |
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