Gregory L. Snitchler

10 MW Class Superconductor Wind Turbine Generators

High temperature superconductor (HTS) technology enables generators with one third the weight and one half the losses of conventional machines. These technologies enable a significant reduction in the size and weight of 10 MW-class generators for direct-drive wind turbine systems and reduce the cost of clean energy relative to conventional copper and permanent-magnet-based generators and gearboxes. With compact and light-weight 10 MW-class HTS generators, installation and low maintenance operation of high power wind turbine systems becomes practical and enable cost-effective access to wind resources. Under a program funded by the NIST-Advanced Technology Program, key generator technologies for a 10 MW class generator have been developed. This paper summarizes work under the NIST and internal programs.

The status of HTS ship propulsion motor developments

The development of ship propulsion synchronous motors with high temperature superconductor (HTS) field windings for Naval electric ship applications has progressed to the point where a full scale motor is now under construction. A 5 MW, 230-rpm prototype ship propulsion motor was built and tested by the Center for Advanced Power Systems (CAPS) on behalf of U.S. Office of Naval Research (ONR). It met or exceeded all its design goals. Currently, a 36.5 MW, 120-rpm ship propulsion motor is being built for delivery to ONR at the end of 2006. This paper presents test results of the 5 MW motor and the status of the 36.5 MW motor

High-field warm-bore HTS conduction cooled magnet

A 7.25 T laboratory magnet utilizing Bi 2223 conductor has been designed, built, and installed at the Naval Research Laboratory. Operating at 21 K at full field, the coil provides field homogeneity of /spl plusmn/1% in a 2-inch warm-bore. The system is conduction cooled with a pair of Leybold single stage cryocoolers that allow cooldown in less than 36 hours and allow extended fast ramp operation. Operation at a total refrigerator input power of 6 kW is facilitated by the use of ASC Cryosaver/sup TM/ HTS current leads. The fully integrated system consists of the magnet, cryogenic system, control and protection system and power supply. This paper presents information on the magnet design, construction and subsequent testing.

2G HTS Wires and the Implications for Motor and Generator Applications

Over the past few years, first generation (1G) high temperature superconductor (HTS) wires have been used to demonstrate large-scale prototype devices, including a 5 MW U. S. Navy motor and an 8 MW synchronous condenser. In addition, the fabrication and testing of larger devices (a 36.5 MW motor and a 12 MW synchronous condenser) are currently underway. Although 1G HTS wire will continue to be a workhorse for demonstrating this technology over the next few years, the lower cost potential of second-generation (2G) HTS wire is driving its rapid development and scale-up. In addition to reporting on key material properties of this wire for coil applications, this paper presents thermal cycling data on 2G racetrack coils, showing excellent robustness under conditions of significant thermal strain. A 2G solenoid coil with a 5 cm inner diameter has achieved 1.5 T at 64 K. These results are a major step in confirming the viability of 2G HTS wire in coil applications.

Practical high temperature superconductor composites for high energy physics applications

Next generation High Energy Physics (HEP) applications consider high magnetic fields (>12 T) at liquid helium temperatures as well as low magnetic fields (/spl sim/2 T) and temperatures above 30 K. Multifilament Bi-2223 conductors have achieved the performance to be considered for these applications. In the low temperature, high magnetic field situation, Bi-2223 offers unique advantages over Nb/sub 3/Sn. Issues of Jc, field quality, magnet stability, strain tolerance, and manufacturability are discussed for accessing the merits of Bi-2223 as compared to Bi-2212 and A-15 materials for HEP.

Long length calorimetric measurement of AC losses of Bi-2223 external field oriented perpendicular to the tape width

AC applications are projected to be a significant market for HTS conductor. The AC magnetic fields perpendicular to the wide face of Bi-2223 conductor (or parallel to the crystallographic c-axis of the oxide superconductor) are responsible for a significant portion of the total loss in AC coils. ASC has developed a calorimetric apparatus which can measure long lengths of conductor in a uniform continuous perpendicular field. This apparatus provides Accurate measurement of interfilament or interstrand coupling losses. Calorimetric measurements from long lengths of twisted multifilamentary conductor are presented.

Magnet cable technology development for high-temperature superconductor composite wire

Abstract Magnet cabling technology has been developed for Bi-based HTS composite wire. Concentric round cabling as well as Rutherford cabling has been proven in > 100 m lengths. For Bi-2223 precursor composite wire, post-cabling deformation is required to achieve high transport engineering current density (Je), and early results have reached 5500 A/cm2 at 77 K and self-field. Cable-and-deform conductor has similar magnetic field retention and anisotropy as conventional, nontransposed multifilament Bi-2223 composites with comparable Je. HTS magnet cabled composites have great potential for providing high Ic, Je, and reducing fabrication cost.

Coil and HTS Development for Fault Current Limiters

Fault current limiters are being developed to limit peak currents in transmission and distribution systems. The authors company* has developed a large, robust, high temperature superconducting (HTS) coil for this application. The development included the design of a composite superconductor and a coil configuration specifically for high transient currents and the resulting high transient forces. The results of the testing of the coil including critical current, transient impedance and ac loss data will be described.

AC Loss Measurements on Multifilamentary BSCCO 2223 High-Temperature Superconductors

A calorimetric method for measuring AC loss in long lengths of high temperature superconductor (HTS) at 77 K has been developed. Complementary systems with resolution down to 1 mW/cc have been installed at Oak Ridge National Laboratory (ORNL) and American Superconductor Corporation (ASC) and give consistent results, confirming the reliability of the technique. AC excitation fields up to 0.25 T and at 5 to 60 Hz are supplied by a multifilament BSCCO solenoid which has been in operation for over a year; this is the world’s first HTS magnet system that performs a useful technical function in a cost-competitive manner. Results are presented on 85 filament BSCCO composite conductors showing dependence suggesting hysteretic losses.

Self-Consistent Current Density Calculation for HTS Coils

The maximum current that a high-temperature superconducting (HTS) coil can achieve is typically calculated assuming uniform current density within the tape in the presence of a flux density gradient within the coil. This solution is not consistent with the current density and flux density, or , dependence of the HTS tapes and more current flows in areas of lower magnetic flux density. For some designs, this error is small, but it can be significant in other cases. This paper presents a method for computing the self-consistent critical current distribution within an HTS by imposing the condition that there is no voltage gradient across the width of an individual tape. The expected increase in critical current is predicted to be as high as 25% for some cases.