Development of Superconducting Rotating Machines
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class of synchronous rotating machines (Super motors and Super generators) that can generically be categorized as Super machines. Compared to the conventional machines of equivalent rating, these Super machines are less expensive, lighter, more compact and efficient. The field windings are made with HTS conductor material which operates at 35-40 K and can be cooled with inexpensive cryocoolers. These advanced machines are attractive for use and at present they offer significant developments in ship propulsion techniques. In many modern ships, propulsion systems are so large and heavy that they force the rest of the ship to be constructed around them. Large ship propulsion system could be made more compact and lighter by application of High Temperature Superconductor (HTS) technology, thus providing relief from this constraint. HTS machine technology is maturing rapidly and marine ship drive applications are expected to benefit greatly from these advances. This paper discusses the application of HTS machines in ship propulsion. On the basis of experience with recent HTS ship propulsion, it can be concluded that the superconducting rotating machines will deliver superior performance both during steady-state and transient modes of operations. HTS rotating machines will be more compact, lighter, and more efficient than the conventional machines. Naval architects can now begin to translate these propulsion system improvements into increased profitability for ship owners and operators. This progress has been achieved due to the recent progress in key enabling technologies, such as HTS wire and cooling systems. Their small size and weight will translate to lower cost. HTS windings operating at an easily attainable temperature level (~35K), and cooled with low cost and dependable off-the-shelf refrigerators, will result in the fielding of highly reliable superconducting machines. The key technologies essential for the successful development of commercially-viable superconductor machines have been proven and are now sufficiently robust, as well as cost-effective. HTS rotating machines for electrical grid stabilization, industrial and ship applications are just now becoming commercially available and can be expected to become increasingly widespread over the next several years.
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Superconducting Rotating Machines.pdf (Size: 157.8 KB / Downloads: 290)
Technology Computer-Aided Design (TCAD)
Swarn S. Kalsi
American Superconductor Corporation, Westborough, MA 01581
Advances in High Temperature Superconductors (HTS) are enabling a new class of synchronous rotating
machines (SuperMotors and SuperGenerators) that can generically be categorized as SuperMachines. Compared to
conventional machines of equivalent rating, these SuperMachines are expected to be less expensive, lighter, more
compact, efficient, and provide significantly superior stable operation in a power system. The field windings are
made with HTS conductor material (BSCCO, or Bi-2223) which operates at 35-40 K and can be cooled with
inexpensive, off-the-shelf cryocoolers available from a number of manufacturers throughout the world. As will be
discussed, these advanced SuperMachines are attractive for use in industrial as well as naval and commercial
maritime industry applications. This paper discusses recent SuperMachine work at AMSC and other companies.
HTS rotating machine technology is maturing rapidly, and electricity producers as well as the end-users will
undoubtedly benefit enormously from these advancements.
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12-04-2011, 09:31 AM
SCG.ppt (Size: 620 KB / Downloads: 216)
SUPERCONDUCTING ROTATING MACHINES
• The higher current density achievable in many superconducting materials tends to make them smaller compared with non-superconducting machines with the same power density.
• General Electric and Westinghouse independently conducted large superconducting generator design studies during the 1970’s, both approaches were based on Low Temperature Superconductor (LTS wire )
• These machines employed LTS wire made up of a niobium-titanium (NbTi) alloy.
• The complexity and cost of the refrigeration equipment, and the challenging nature of thermal isolation systems that are necessary for allowing LTS materials to operate at an ultra-low 4K, have made rotating machine applications a prohibitive concept.
• American Superconductor Corporation (AMSC) has built and tested a 5000 hp, 1800-RPM motor for industrial market.
• High-temperature superconductors become superconducting at more easily obtainable liquid nitrogen temperatures.
HTS Wire Status
• High temperature superconductor bismuth strontium calcium copper oxide (BSCCO-2223) manufactured commercially by American superconductor (AMSC).
• It is able to carry more than 140-times the electrical current of copper wire of the same cross section, and is robust enough to meet commercial requirements
• However, a newer yttrium barium copper oxide (YBCO) superconductor has been developed .
• The major components of a rotating machine employing HTS winding
• Only the field winding employs HTS cooled with a cryocooler subsystem to about 35-40K
• The cryocooler modules are located in a stationary frame and a gas, such as helium, is employed to cool components on the rotor.
• Advantages and Disadvantages of superconducting electric machines Compared with a conventional conductor machine.
• Reduced resistive losses but only in the rotor electromagnet.
• Reduced size and weight per power capacity without considering the refrigeration equipment.
• The cost, size, weight and complications of the cooling system.
• Motor bearings need to be able to withstand cold or need to be insulated from the cold rotor.
HTS Machine Application In Ship Propulsion
HTS alternating current (AC) synchronous motors provide a very attractive alternative:
• Greater than 98% efficiency across a wide range of ship operating profiles, which can lower fuel consumption and ship operating costs
• Inherently quiet with low weight rotors, no iron teeth.
Market Potential :
“Electric marine propulsion is a market of approximately $250 million that is growing strongly ”.
Benefits Of Using Superconducting Machines
• Lower operating costs
• Less vibration and noise
• Smaller size and weight
• Increased stability
• New technology in the form of a litz-wire bar
• This could contribute to an overall performance improvement, especially in efficiency (expected 0.1...0.3%).
• Litz wire made out of many thinner isolated Superconducting wires.
• Litz wire is more concentrated for high frequency applications where the skin effect is more pronounced.
• Today’s motors are fundamentally similar to the electric motors designed over a century ago.
• The motor manufacturing industry has seen only incremental improvement in product design over the past years.
• The advent of high temperature superconductivity has created the opportunity in the technology of motors.
• The cost, size, weight and efficiency benefits of superconducting machines will significantly change the dynamics of the motor manufacturing industry and the motor user market .
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03-05-2011, 10:25 AM
Advances in High Temperature Superconductors (HTS) are enabling a new class of synchronous rotatingmachines (SuperMotors and SuperGenerators) that can generically be categorized as SuperMachines. Compared toconventional machines of equivalent rating, these SuperMachines are expected to be less expensive, lighter, morecompact, efficient, and provide significantly superior stable operation in a power system. The field windings aremade with HTS conductor material (BSCCO, or Bi-2223) which operates at 35-40 K and can be cooled withinexpensive, off-the-shelf cryocoolers available from a number of manufacturers throughout the world. As will bediscussed, these advanced SuperMachines are attractive for use in industrial as well as naval and commercialmaritime industry applications. This paper discusses recent SuperMachine work at AMSC and other companies.HTS rotating machine technology is maturing rapidly, and electricity producers as well as the end-users willundoubtedly benefit enormously from these advancements.
The advent of high-temperature superconductivity hascreated the opportunity for a quantum leap in thetechnology of large electric machines. HTS-basedmotors and generators will be smaller, lighter, moreefficient, and less expensive to manufacture andoperate than conventional machines. The potentiallysignificant cost, size, weight and efficiency benefits ofsuperconducting machines will change the dynamics ofthe electrical machinery industry. This unique situationleads to reduced manufacturing costs.The initial use for HTS motors will likely be intransportation applications, particularly naval andcommercial ship (marine) electric propulsion, wherecritical size and weight savings will provide a keybenefit by increasing ship design flexibility. Electricdrive has already penetrated the cruise ship segment ofthe market because of its marked advantages overcompeting mechanical systems. The increased powerdensity and operating efficiency as well as otherbenefits of HTS based marine propulsion systems willsignificantly further expand the attractiveness ofelectric propulsion systems. HTS motors are ideal foruse in pumps, fans, compressors, blowers, and beltdrives deployed by utility and industrial customers,particularly those requiring continuous operation.These motors will be suitable for large processindustries such as steel milling, pulp and paperprocessing, chemical, oil and gas refining, mining,offshore drilling, and other heavy-duty applications.Superconducting wire in its Low TemperatureSuperconductor (LTS) form has been in widespreaduse now for over 30 years, and commercialapplications today range from high-powered particleaccelerators to sensitive resonance imaging systemsutilized for medical diagnostics. General Electric andWestinghouse independently conducted largesuperconducting generator design studies during the1970’s; both approaches were based on LTS wire.General Electric also built and tested a 20 MVAsuperconducting generator in the 1970’s, and aJapanese consortium built and tested a 70 MWgenerator during the 1990’s. These machinesemployed LTS wire made up of a niobium-titanium(NbTi) alloy. The high current density achievable insuperconducting electromagnets makes it possible tocreate very compact and power-dense rotatingmachinery. However, even at such large ratings, thecomplexity and cost of the refrigeration equipment, andthe challenging nature of thermal isolation systems thatare necessary for allowing LTS materials to operate atan ultra-low 4K, have made any conceivablecommercialization of this early superconductingtechnology in rotating machine applications aprohibitive concept.However, rapid advances in the development of HTSwire over the past 13 years have resulted insuperconducting electromagnets that can operate atsubstantially higher temperatures than those made ofLTS materials, and which as a consequence can utilizerelatively simpler, less costly, and more efficientrefrigeration systems. These factors make HTS wiretechnically suitable and economically feasible for usein the development and commercialization of motorand generator applications at power ratings much lowerthan could be considered with LTS wire.American Superconductor Corporation (AMSC) hasbuilt and tested a 5000 hp, 1800-RPM motor forindustrial market. They have also developed a designfor a 5 MW HTS (“model”) model motor for shippropulsion; this motor demonstrates technologies to beemployed in a full-size 25 MW, 120 RPM HTS motor.The model motor is scheduled for completion andtesting by the end of 2002. AMSC has also developeda conceptual design for a 50 MW, 3600-RPM HTSgenerator. Other companies are also developingSuperMachines. A 1000 hp, 1800-RPM motor fundedunder the SPI program, and built by a team consistingof Rockwell Automation, AMSC, and others, wassuccessfully operated in May 2000. Siemensdemonstrated a 550 hp, 1800-RPM motor in thesummer of 2001. GE has just won a DoE-SPI contractfor the design and development of a 100 MVA HTSgenerator.The discussion in this paper is centered on applicationsof HTS SuperMachines to an All-Electric Ship. Figure1 shows a single line diagram for a ship electricalsystem employing superconducting generators,propulsion motors and general-purpose industrialmotors.
II. HTSWIRE STATUS
Over the past ten years, the performance ofmultifilamentary composite HTS wire has continuallyimproved. Currently, AMSC is producing this wire at arate of about 500km/year and the end of 2002 willproduce 10,000 km/year in its new factory. This Bi-2223 high current density wire is available forindustrial applications and prototypes. Bi-2223 highstrength reinforced wire is able to withstand close to300 MPa tensile stress and 0.4% tensile strain at 77K.Reinforced wires provide a mechanically robust andreliable product, which are suitable for making highperformance prototype propulsion motors andgenerators.
III. SUPERMACHINE TOPOLOGY
The major components of a rotating machineemploying HTS winding is shown in Figure 2. Onlythe field winding employs HTS cooled with acryocooler subsystem to about 35-40K. The cryocoolermodules are located in a stationary frame and a gas,such as helium, is employed to cool components on therotor. The stator winding employs conventional copperwinding but with a few differences. The stator windingis not housed in conventional iron core teeth becausethey saturate due to high magnetic field imposed by theHTS winding.
Compared to conventional generators, HTS generatorsare expected to be less expensive, lighter, morecompact, efficient and reliable, and significantlysuperior at maintaining power system stability. Theyalso exhibit higher efficiency under partial loadconditions and could operate as virtual condenser todeliver its rated current.The SuperGenerator1 shown in Figure 3 has threemajor subsystems; 1) rotor, 2) rotor cooling and 3)stator. Physically, this generator is expected to beabout half (1/2) the length and two-thirds (2/3) thediameter of a conventional machine. This generator hasa low synchronous reactance of 0.28 pu but thetransient and sub-transients reactances are similar tothose of conventional machines. The overall efficiencyof the generator is 98.6% which is retained down to1/3rd of the rated load. The majority of losses (65%) arein the conventional copper armature winding. Thecryogenic cooling system power consumption ismerely 2% of the total losses in the machine.SuperGenerator produces nearly clean AC voltage inthe stator winding. Both rotor and stator windingsgenerate minimal harmonics. The field windingproduces 2% of 5th harmonic voltage in statorwinding; all other harmonics are negligible.
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