High Temperature Superconducting Synchronous Motor Research Articles

Numerical analysis of 40 MW HTS motor electromagnetic characteristics for ship electric propulsion

In recent years, with the development of ship electric propulsion system, High Temperature Superconducting (HTS) motors have gained attention as a promising potential resolution due to their high-power density and the progression of cryogenic refrigeration technology. We present an electromagnetic characteristics numerical analysis of 40 MW, 120 rpm, HTS synchronous motor which is a semi-superconducting motor: in fact, it has a superconducting rotor composed of YBCO material and a conventional stator. Combining electric resistivity variation of rotor copper shielding sleeve in low temperature environment and YBCO coil critical current, the electromagnetic behavior of the 40 MW HTS synchronous motor is analyzed with non-ferromagnetic stator support structure. To assess the effects of varying stator winding currents and thickness on eddy current losses of the copper shielding sleeve, calculations were done, and a preliminary discussion was initiated. This study has certain reference significance for electromagnetic design and optimization of multi-ten MW HTS motors, especially used in ship electric propulsion system.

Investigation on Effect of Shape of HTS Pole Coil on Airgap Magnetic Field of HTS Synchronous Motor

The High Temperature Superconducting (HTS) synchronous motors offer considerably higher torque and power densities along with higher efficiencies for strategic and critical industrial applications. The most widely explored airgap based topology for HTS synchronous motors has conventional copper windings in stator and HTS pole coils in the rotor. The shape of these rotor pole coils affects various electrical parameters of the motor. In this paper, a detailed investigation has been carried out on effect of shape of HTS pole coil on airgap magnetic field and rated open circuit characteristic (OCC) of an 8 MW HTS synchronous motor along with its other parameters like pole coil excitation current, peak magnetic field inside the motor, maximum perpendicular magnetic field on HTS tape and operating temperature of HTS pole coils through FEM based electromagnetic analysis. Based on the results of electromagnetic analysis, the optimum shape of HTS pole coil has been finalised.

Charging Optimization of a YBCO Racetrack Coil With a Linear-Motor Type Flux Pump for an HTS Synchronous Motor

This paper presents the preliminary charging test results of an high temperature superconducting (HTS) no-insulated (NI) double racetrack coil with the linear-motor type flux pump. The racetrack coil is designed and manufactured for the rotor field winding of a 16.9-kW-class HTS synchronous motor. This HTS synchronous motor was designed to employ a contactless static excitation device (CSED), i.e., the linear-motor type flux pump, which can charge the racetrack coil installed in the rotating machine in contactless manner. In the experiment, the major components of the 16.9-kW-class HTS synchronous motor, such as the racetrack coil and the CSED, had been manufactured, tested and optimized. The charging performance was tested in 77 K. In particular, we optimize the CSED of the HTS synchronous motor by testing different wavelengths of flux pumps and different superconducting stator wires, so as to select the appropriate wavelength of the flux pump and stator wire to optimize the operation of the synchronous motor.

Design, Fabrication, and Testing of a YBCO Racetrack Coil for an HTS Synchronous Motor With HTS Flux Pump

An experimental platform of high temperature superconducting (HTS) synchronous motor with HTS flux pump has been designed and under construction. The HTS flux pump as an exciter eliminates thermal load from the metal current leads, which will reduce the cryogenic volume and improve the efficiency of the HTS machine. A finite element model (FEM) using T-A formulation was developed to analyze the electromagnetic characteristics of a double-pancake (DP) racetrack coil. The no-insulation (NI) racetrack coil wound by YBCO tapes was fabricated with a winding machine in our lab. We proposed a novel mechanical structure to avoid the impregnation of epoxy resin and make the coil more reliable. The turn-to-turn pressure of the racetrack coil can be changed by driving the screws on the straight section. Besides, we manufactured a rotating HTS flux pump as a DC power supply to charge the racetrack coil without contact. The self-field critical current test with a direct current (DC) power supply and the charging experiment with the HTS flux pump of the constructed YBCO racetrack coil were performed at 77 K.

Design and Study of a 2G HTS Synchronous Motor With Brushless HTS Flux Pump Exciters

A high temperature superconducting (HTS) synchronous motor with brushless HTS flux pump exciters was designed and is under construction. This HTS synchronous motor is composed of copper armature windings, HTS field windings, HTS flux pump exciters, vacuum chamber, rotary gas seal, etc. The double racetrack-type HTS field coils are wound with second-generation (2G) YBCO tapes and cooled directly by the cold heads. The designed operation temperature is about 30 K. An HTS flux pump was designed to be used as DC power supply to inject large currents into the HTS field coils, which eliminates the slip ring in the motor and avoids thermal load from current leads. The novel design of multiple sources enables us to control the excitation current of the HTS field winding for each pole separately and to prevent all the series field coils from stopping at the same time due to the quench of one coil. To describe the performance characteristics of the HTS motor, an electromagnetic design was carried out with 2-D finite-element method models. Finally, the total losses of HTS synchronous motor are calculated. The next step is to manufacture and install the HTS exciters, HTS field windings, etc. into the HTS synchronous motor.

Degradation of Critical Current in an HTS Tape With Combined Bending and Torsion Considering Curvature of Elliptical Shape

Degradation of critical current ( I c) in a high-temperature superconducting (HTS) tape under bending conditions had been previously investigated. These investigations were focused on only either bending or torsion. A rotating flux pump is used to study the charging characteristics of an HTS synchronous motor. In order to design the rotating flux pump connected in series, the elliptical winding applied together with combined bending and torsion is essential. Therefore, in this paper, the critical current considering curvature of elliptical shape is measured with regard to nine kinds of mandrels. The shapes of the mandrels are a tall prolate ellipsoid, oblate ellipsoid, and semicircle. The diameters of each shape are 20, 30, and 40 mm, respectively. The experiments are mainly composed of three conditions: straight, bending, and combined bending and torsion. Finally, the experimental observations have been compared with the theoretical predictions.

Design and Analysis of Cooling Structure on Advanced Air-Core Stator for Megawatt-Class HTS Synchronous Motor

A general high-temperature superconducting synchronous motor (HTSSM) is designed and manufactured with an air-core structure, which eliminates the laminated iron core to concentrate the linkage flux in conventional rotor and stator. In an air-core structure, a nonmagnetic material such as glass fiber-reinforced plastic (GFRP) is used as an armature winding supports to avoid saturation of magnetic field density in the stator core and to reduce the weight and harmonics of the motor. However, GFRP air-core supporters make heat dissipation difficult due to the very low thermal conductivity of GFRP, which makes sustainable and stable operation of HTSSMs impossible. Therefore, in this paper, the concept of advanced air-core stator (AACS) is presented to enhance the cooling performance of a conventional GFRP air-core stator. The AACS concept pertains to the introduction of thermal conductive materials on an armature supporter to replace the GFRP material of a conventional air-core stator. The AACS concept structure for a 1.5-MW-class HTSSM was designed and analyzed using three-dimensional electromagnetic and thermal finite element method.

Analysis of the Mechanical Characteristics of a 17-MW-Class High-Temperature Superconducting Synchronous Motor

This paper presents an analysis of the mechanical characteristics of a 17-MW-class high-temperature superconducting (HTS) synchronous motor. The fundamental electromagnetic, structural, and thermal design must be accompanied to maintain the reliability of an HTS rotating machine when designing an HTS synchronous motor with an HTS wire with a high current density instead of a copper wire used in a conventional rotating machine. Therefore, we analyze the structural characteristics from two perspectives using three-dimensional (3D) finite-element analysis for the structural design of a 17-MW-class HTS synchronous motor that is intended to be utilized for ships with electric propulsion.

Trial Test of a Bulk-Type Fully HTS Synchronous Motor

The world's first bulk-type fully high temperature superconducting synchronous motor (HTS-SM) was assembled and tested in our laboratory at the University of Cambridge. The fully HTS-SM was designed with 75 Y123 HTS bulks mounted on the surface of the rotor and six air core 2G HTS racetrack coils used for stator windings. We successfully applied a light fan load test for this fully HTS-SM at its operating temperature of 77 K. The detected decay of the trapped magnetic flux densities at the centre of the HTS bulks was up to 16.5% after 5 h of synchronous rotation. Due to the high current density of the HTS material, the ac stator field for the 2G HTS winding was 49.2% stronger compared with a comparable copper winding. In the meantime, we estimated that the efficiency was about 86% potentially under stable low frequency rotation at 150 r/min. The results show that the performance of this HTS motor is acceptable for practical applications.

Control and Operation of a High Temperature Superconducting Synchronous Motor

We have built a four-pole high temperature superconducting (HTS) permanent magnet synchronous motor (PMSM) in our lab. At this stage, the HTS PMSM uses two 2G HTS racetrack coils, which are YBCO wires, type 344 from AMSC, and four conventional copper coils as stator windings. 75 YBCO bulks are mounted on the surface of the rotor. After the pulsed field magnetization system had been developed and tested in our lab in 2011, the rotor can trap a four-pole magnetic field. This makes HTS bulks possible for motor application, other than HTS coils. The HTS PMSM can successfully run at a low speed of around 150 rpm for an initial test. This paper states theoretical and practical works on the HTS PMSM's operation including HTS motor drive development and its application.

Helium-Neon Gas Mixture Thermosyphon Cooling and Stability for Large Scale HTS Synchronous Motors

Commercial high-temperature superconducting (HTS) wires restrain us to an operation temperature ranging from 20 to 40 K for field-pole magnets applied to rotating machinery. We have proposed to employ a mixture of helium and neon gas in a closed-cycle thermosyphon based on a GM cryo-refrigerator. In this paper, we discuss the temperature stability of the evaporator created by a helium-neon mixture cooling coupled with a closed-cycle thermosyphon, upon an external heat load on a 100-kW-grade HTS synchronous machine. A home-made cooling system, including the condenser, was designed. The evaporator was assembled within the motor in accordance with thermal and mechanical analysis. The cooling of the evaporator with the 100-kW-grade HTS synchronous motor was applied against a variable heat load equivalent with the actual HTS rotor field poles. We report these results and propose its potential application to a large-scale ship propulsion motor.

Conceptual Design of a Field Coil for 5 MW HTS Synchronous Machine

Compared with a conventional rotating machine, a superconducting rotating machine fabricated by High Temperature Superconducting (HTS) tape has superior performance and efficiency due to the HTS field coil for the rotor which can generate high magnetic flux intensity. The two primary factors for the design of the HTS rotational machine are how to construct the optimal magnetic field path through the air gap located between the rotor and the stator and how to enhance the linkage magnetic flux density between the armature coil in the stator and the field coil in the rotor. A 5 MW HTS motor for ship propulsion is planned for development in early 2011 by a Korean collaboration group of KERI and DOOSAN Heavy Industry. As a part of this R&D efforts, we designed and analyzed the field coil for a 5 MW HTS synchronous motor. In this paper, the computational results of the magnetic field distribution on the whole winding regions of the HTS field coil of the superconducting rotating machine will be also presented and discussed.

Numerical assessment of efficiency and control stability of an HTS synchronous motor

A high temperature superconducting (HTS) permanent magnet synchronous motor (PMSM) is designed and developed in Cambridge University. It is expected to become cost competitive with the conventional PMSM owing to its high efficiency, high power density, high torque density, etc. The structure and parameters of HTS PMSM are detailed. Both AC losses by transport current and applied filed in stator armature winding of HTS PMSM are also analyzed. Computed and simulated results of the characteristics of the HTS PMSM and conventional PMSM are compared. The improvement on stability of direct torque control (DTC) on the HTS PMSM is estimated, and proved by simulation on Matlab/Simulink.

Electrical performance analysis of HTS synchronous motor based on 3D FEM

A 1-MW class superconducting motor with High-Temperature Superconducting (HTS) field coil is analyzed and tested. This machine is a prototype to make sure applicability aimed at generator and industrial motor applications such as blowers, pumps and compressors installed in large plants. This machine has the HTS field coil made of Bi-2223 HTS wire and the conventional copper armature (stator) coils cooled by water.The 1-MW class HTS motor is analyzed by 3D electromagnetic Finite Element Method (FEM) to get magnetic field distribution, self and mutual inductance, and so forth. Especially excitation voltage (Back EMF) is estimated by using the mutual inductance between armature and field coils and compared with experimental result. Open and short circuit tests were conducted in generator mode while a 1.1-MW rated induction machine was rotating the HTS machine. Electrical parameters such as mutual inductance and synchronous inductance are deduced from these tests and also compared with the analysis results from FEM.

Design of Damper to Protect the Field Coil of an HTS Synchronous Motor

High Temperature Superconducting (HTS) synchronous motors consist mainly of rotational (HTS coil) and stationery (copper coil) parts. The HTS coil running at a synchronous speed is not influenced by the magnetic field generated by the stator coil but is affected considerably at the initial or transient operation. Therefore, computational analysis to determine the optimal design of the damper is an important factor in protecting the field coil of a HTS synchronous motor. This paper presents the optimal design parameters of the damper for a 5 MW HTS synchronous motor using the computational analysis of the transient characteristics of the stator current, which is proportional to the alternating magnetic field of the stator coil.

Loss analysis of a 1 MW class HTS synchronous motor

The HTS (High-Temperature Superconducting) synchronous motor has advantages over the conventional synchronous motor such as smaller size and higher efficiency. Higher efficiency is due to smaller loss than the conventional motor, so it is important to do loss analysis in order to develop a machine with higher efficiency. This paper deals with machine losses those are dissipated in each part of a HTS synchronous motor. These losses are analyzed theoretically and compared with loss data obtained from experimental results of a 1 MW class HTS synchronous motor. Each machine loss is measured based on IEEE 115 standard and the results are analyzed and considered based on the manufacturing of the test machine.

Electrical parameter evaluation of a 1 MW HTS motor via analysis and experiments

A 1MW class HTS (high-temperature superconducting) synchronous motor has been developed. Design concerns of the developed motor are focused on smaller machine size and higher efficiency than conventional motors or generators with the same rating simultaneously reducing expensive Bi-2223 HTS wire which is used for superconducting field coil carrying the operating current around 30K (−243°C). Influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power during motor and generator operation. The developed motor was also analyzed by three-dimensional electromagnetic FEM (finite element method) to get magnetic field distribution, inductance, electromagnetic stress and so forth.This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of Neon thermosiphon mechanism and the stator (armature) coil is cooled by water through hollow copper conductor. This paper also describes evaluation of some electrical parameters from performance test results which were obtained at steady state in generator and motor mode of our HTS machine.

High-Temperature Superconducting Synchronous Motors: Economic Issues for Industrial Applications

High-temperature superconducting (HTS) materials offer the capability to reduce losses in large industrial motors (greater than 1000 hp in rating) by 50%. This loss reduction can be accompanied by an overall motor-size reduction. In this paper, the application of high-temperature superconductors in high-horsepower electric motors is described, and the potential benefits of these motors are discussed. The economic viability of HTS-based electric motors for industrial applications depends upon the cost of the superconducting wire. A discussion of wire component costs for readily available first-generation HTS wire as well as the future lower cost second-generation HTS wire is presented, showing that economically viable HTS-based motors will require second-generation wire. A review of the state of the art in industrial-motor laboratory-prototype demonstrations of HTS-based motors is presented, showing the rapid advancement of this technology. The application advantages of HTS motors in pump and fan systems are also discussed.

Performance test of a 1 MW class HTS synchronous motor for industrial application

This paper deals with development activities of high temperature superconducting (HTS) synchronous motor at DOOSAN heavy industry and Korea Electrotechnology Research Institute (KERI) in Korea, and is sponsored by DAPAS program which is supported by Korean government. The final aim of the project is realization of HTS motor in the field of industry such as large driving pumps, fans and compressors for utility and industrial environments. At present time, 1 MW HTS motor is developed for the purpose to fully represent the design and manufacturing issues for the larger capacity machine. The number of pole and rotating speed of machine are 2 pole and 3600 rpm. The HTS field coil of the developed motor is cooled by way of neon thermosyphon mechanism and the stator coil is cooled by water through hollow copper conductor. This paper describes status of 1 MW HTS motor development, such as design, fabrication and performance test results, which was conducted at steady state in generator mode and motor mode.

Parametric Design for Superconducting Synchronous Motor With 3D Equivalent Magnetic Circuit Network Model

This paper proposes an effective parametric design for high temperature superconducting (HTS) synchronous motors with 3D equivalent magnetic circuit network (EMCN) method. Proposed design process consists of 5 steps which are electric design, mechanical design, characteristic analysis for field and armature, and motor characteristic analysis. Especially, in order to predict the performance of HTS synchronous motors, the variation of output power characteristics according to the variation of back electromotive force (BEMF) and inductance is analysed in electric design. Reliability of proposed design process and developed program is verified through the comparison of the results of commercial program using 3D finite element analysis (FEA) method.