Bruce B. Gamble

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 performance of a 5 MW high temperature superconductor ship propulsion motor

A 5 MW, 230 RPM, 6-pole high temperature superconductor (HTS) ship propulsion motor is presently under test at the Center for Advance Power Systems (CAPS). This paper provides a summary of the key design features of the motor, predicted performance, factory test results and extended test results to date at CAPS. This motor was designed and built under the U.S. Navys Office of Naval Research (ONR) funding (Contract #N00014-02-C-0190) to address the next generation of electric ship propulsion systems. HTS motors are characterized by high power density, quiet operation and high efficiency. HTS air-core motors have unique electrical characteristics and therefore require dynamic testing to validate all modes of operation. The test program at CAPS is designed to address dynamic performance and simulation of this class of propulsion motor. The motor has been operated at 5 MW load for over 3 hours at CAPS.

Full Power Test of a 36.5 MW HTS Propulsion Motor

This paper discusses the full-power testing of a 36.5 MW High Temperature Superconductor (HTS) propulsion motor at the Navys Land Based Test Site (LBTS) located in Philadelphia, PA. This motor was developed under funding from the Office of Naval Research and passed no-load factory testing at Philadelphia in March 2007. The Naval Surface Warfare Center (Carderock Division - Philadelphia site) designed and installed a test facility at LBTS to support full-power/full-torque testing of the HTS motor delivered to the Navy in 2007. The facility, test plan and full-power and full-torque test results of the HTS propulsion motor are presented. These test results provide the final substantiation that this technology is ready for integration in to a Navy electric drive combatant.

Design and test of current limiting modules using YBCO-coated conductors

Within the cooperation between American Superconductor Corporation (AMSC) and Siemens Corporate Technology we have investigated the fault current limiting performance of YBCO-coated conductors (also called second-generation or 2G HTS wires) stabilized with stainless steel laminates. Design rules for the length and width of the wire depending on utility grid requirements have been established. Bifilar coils have been manufactured and tested with a typical limitation period of 50?ms under stepwise increasing voltage loads to determine the maximum temperature the wires can withstand without degradation. Coils have been assembled into limiter modules demonstrating uniform tripping of the individual coils and recovery within seconds. At present this cooperation is proceeding within a joint project funded by the US Department of Energy (DOE) that encompasses the design, construction and testing of a 115?kV FCL for power transmission within a time frame of 4?5 years, and additional partners. Besides AMSC and Siemens, Nexans contributes the high voltage terminations and Los Alamos National Lab investigates the ac losses. Installation and testing are planned for a Southern California Edison substation. The module planned for the transmission voltage application consists of 63 horizontally arranged coils connected in parallel and series to account for a rated current of 1.2? kArms and voltage of 31?kVrms plus margins. The rated voltage of the module is considerably lower than the line to ground voltage in the 115?kV grid owing to our shunted limiter concept. The shunt reactor connected in parallel to the module outside the cryostat allows for adjustment of the limited current and reduces voltage drop across the module in case of a fault. The fault current reduction ratio is 42% for our present design. A subscale module comprising six full-size coils has been assembled and tested recently to validate the coil performance and coil winding technique. The module had a critical current of 425? ADC and a nominal power of 2.52?MV?A at 77?K. A complete series of tests with applied voltage up to 8.4? kVrms, prospective short circuit current up to 26.6? kArms and variation of phase angle at initiation of the fault has been performed. After more than 40 switching tests the critical current of the module remained unchanged, indicating that no degradation of the wire occurred.

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

Status of the 1000 HP HTS motor development

Progress has been made in the development of high efficiency HTS motors with the aid of Department of Energy funding under the Superconductivity Partnership Initiative. This effort includes the fabrication and testing of synchronous motors with HTS field windings. The objectives of this development effort include saving half the losses of conventional motors in a package with half the volume. In Phase I of the present program, a 125 HP synchronous motor with an HTS field winding was designed and tested to levels in excess of 200 HP. This paper summarizes the status of a 1000 HP motor development which is part of a Phase II effort. The program elements to be reviewed include the overall design characteristics of the motor, the status of the field coils and refrigeration system, and a description of other components of the 1000 HP motor system. The 1000 HP motor fully represents the design issues to be addressed in the 5000 HP motor also to be developed in Phase II.

Power applications of high-temperature superconductors: status and perspectives

The potential of superconductors to have a revolutionary impact on how electric power is generated, delivered and used has long been recognized. The first superconducting power-grid application to achieve full commercial status is superconducting magnetic energy storage (SMES); the magnets of these systems have so far been fabricated primarily with metallic low-temperature superconductors (LTS). Although LTS prototypes have been demonstrated for motors, generators, power cables, transformers and current limiters, high-temperature superconducting (HTS) systems offer striking economic and system reliability advantages and are now seen as the central vehicle for broad commercialization of superconductivity in the power grid. Operating at temperatures from 30 to 80 K, they open the door to highly simplified cryogenics and increased stability, which result in economic systems not feasible with LTS. HTS prototypes at commercial power levels have already been demonstrated, particularly power transmission cables and motors. Key merits as well as remaining open technical challenges for such HTS applications are reviewed in this paper.

The status of HTS motors

The status of high temperature superconducting (HTS) motor development is presented. HTS synchronous machines have been under development for over 12 years around the world. The unique characteristics for selected applications such as ship propulsion are discussed. The beneficial characteristics of air core HTS motors for ship propulsion include high power density, high efficiency and low noise production. This paper also addresses recent developments including a 5,000 HP 1800 RPM 4 pole prototype and the ongoing construction of a 5 MW 230 RPM motor. The 1800 RPM motor is a prototype constructed to validate technologies for industrial motors and generators and the 230 RPM motor is being constructed to validate technologies for ship propulsion motors in the range of 25 MW and 120 RPM.

HTS generator topologies

A variety of topologies have been studied for superconducting generators. The superconducting generators constructed over the past 40 years using low temperature superconductors were built with iron located only in the stator core. The performance characteristics of HTS has led to the consideration of topologies with iron in the center of the rotor inside the field winding, iron in the rotor pole faces and iron in the armature teeth. As the reluctance of the flux path is decreased, the amount of superconductor is minimized and the forces on the rotor and stator coils are reduced. The impact of this addition of iron on other machine parameters including transient stability following a system fault is addressed in this paper

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.