Showing papers by "Guangtong Ma published in 2010"

3-D Modeling of High- $T_{c}$ Superconductor for Magnetic Levitation/Suspension Application—Part I: Introduction to the Method

Abstract: A magnetic levitation technique with high-Tc superconductor (HTS) has received significant interest for a wide range of applications after its discovery due to its unique inherent stability, which gives a fundamental significance to evaluate the HTS magnetic levitation in both experiment and calculation. To numerically investigate the HTS magnetic levitation, a 3-D model describing the electromagnetic property of the HTS, including its anisotropic behavior, was established by incorporating the current vector potential and Helmholtz's theorem. In addition to the commonly considered nonlinear E-J characteristic in the reported calculation, we introduce an elliptical model to formulate the angular dependence of the critical current density Jc resulting from the anisotropic behavior of the HTS. To numerically resolve the governing equations of the 3-D model, Galerkin's finite-element method and the Crank-Nicolson-θ method were employed to discretize the governing equations in space and time domains, respectively. The obtained algebraic equations were firstly linearized by the Newton-Raphson method, and then an extended format of the incomplete Cholesky-conjugate gradient method was applied to solve the linear algebraic equations. The 3-D model was implemented by a self-written numerical program based on a VC++ platform to calculate the magnetic force of a bulk HTS exposed to applied field generated by a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. In this paper, we present the numerical results of the levitation force of a moving bulk HTS above the PMG with different mesh densities and number of time steps. This presents a preliminary validation of the 3-D model proposed in this paper.

3-D Modeling of High- $T_{c}$ Superconductor for Magnetic Levitation/Suspension Application—Part II: Validation With Experiment

Abstract: In this paper, the 3-D model proposed in Part I of this study is verified in detail on the basis of a levitation/suspension system composed of a rectangular single-domain Y-Ba-Cu-O and a cylindrical Nd-Fe-B magnet or a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. The magnetic forces along the vertical direction perpendicular or the transverse direction parallel to the surface of the PMG (or magnet) were calculated and compared well with the measured data under vertical and transverse displacements. The computed results of the induced current distribution within the Y-Ba-Cu-O domain, as well as the magnetic field profiles in the Y-Ba-Cu-O and its vicinal region, were also presented and discussed.

A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system

Abstract: Thrust measurements were performed on a coil made of a YBa2Cu3O7 − δ coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of IDC = 30 A for the superconducting coil and alternating current of IAC = 9 A for the stator coils, a thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back-plate, thrust was increased by 70%.

Numerical Investigation of the Lateral Movement Influence on the Levitation Force of the Bulk HTS Based on a 3-D Model

Abstract: On the basis of a 3-D model of the high- superconducting maglev, the characteristics of the levitation force (LF) of a bulk high-Tc superconductor (HTS) under continuous lateral movement was numerically investigated. The Functional rule of the influencing factors, such as field-cooling height (FCH), levitation height (LH), maximum lateral displacement (MLD), and material property, was demonstrated. The results indicate that, for the case with a shorter MLD, and better material property, the LF decay due to lateral movement is more remarkable. Finally, the Pre-Loading, i.e., make the bulk HTS trap more fluxes before working, was also simulated and its validation to reduce the LF decay is confirmed.

Levitation Force Transition of High-Tc Superconducting Bulks in Varying External Magnetic Field

Abstract: In practical application of a High-Tc Superconducting (HTS) maglev vehicle, the onboard HTS bulks are inevitably exposed to a varying inhomogeneous field due to present processing and assembling technology of the permanent magnetic guideway (PMG). To explore the influence on the levitation forces of YBa2Cu3O7-x bulk samples in such changing external magnetic field due to different traveling speeds, we experimentally investigated the general transition of said levitation force under such varying external field simulated by a spinning circular PMG. The force waves attenuated in accordance to the varying of the applied field dependent on the PMG's rotating speed: attenuating when speeding up and rising slightly when speeding down. This observed phenomenon is of great importance in design and application of the HTS maglev system.

High-temperature superconduction magnetic suspension radial bearing

Abstract: The utility model discloses a high-temperature superconductive magnetic suspension radial bearing, which is characterized in that a rotor (6) consisting of an axially magnetized permanent magnet (61) and a magnetic concentrator (62) is fixed on an outer ring of a rotating shaft (5); an outer ring of the rotor (6) is circled by a low-temperature liquid nitrogen container (2); a copper box (8) is fixed on the inner wall of the inside of the low-temperature liquid nitrogen container (2); and a high-temperature superconductive block serving as a stator (3) is filled in the copper box (8). The bearing has the advantages of high rigidity, good stability, little loss, high rotating speed, small volume, simple structure and large bearing capacity.

Influence of Auxiliary Permanent Magnet on the High- $T_{\rm c}$ Superconductive Hybrid Maglev System

Abstract: The high-Tc superconductive (HTS) hybrid Maglev with the auxiliary permanent magnet (PM) is a useful method to improve the system load density and stiffness. The auxiliary PM changes the magnetic circuits and increases the instability of the Maglev system. To investigate the levitation performance, different HTS hybrid Maglev arrangements involving PM and bulk HTS were tested above the permanent magnet guideway. Some useful conclusions and reference for relative design can be found from the experimental results and analyses.

A Method to Increase the Lateral Reversible Region of Bulk YBCO Above a Permanent Magnet Guideway

Abstract: Lateral reversible region of the bulk high-Tc superconductor (HTSC) above the permanent magnet guideway (PMG) is a key parameter for the high-Tc superconducting (HTS) maglev system. The lateral stability and guidance force are proportional to the width of the lateral reversible region. When the lateral displacement of the bulk HTSC exceeds the reversible region, the maglev system will return to a new lateral equilibrium position. The method with the use of pre-displacement can successfully increases the lateral reversible region of the bulk HTSC. By the correct choice of the maximum lateral offset and a new starting point, the instability of flux motion can be suppressed. Unsuitable usage of this method will cause the intersection of guidance force and reduce the reversible region. Analyses based on the magnetizing history and pinning metamorphoses well explain the experimental results. Difference between this method and the pre-load method is also discussed in this article.

A High-Temperature Superconducting Magnetic Helix Transmission Mechanism

Abstract: A novel high-temperature superconducting (HTS) magnetic helix transmission mechanism is introduced to overcome the inevitable friction and wear of a traditional mechanical helix transmission mechanism. It is based on the principle that a high-temperature superconductor can move in one direction with a uniform magnetic field without any resistance. The mechanical property of this mechanism is theoretically studied. Results show that the driving torque and axial carrying capacity are closely dependent on the lead angle of the magnetic bolt.

High temperature superconductive magnetic suspension screw drive pair

Abstract: A high temperature superconductive magnetic suspension screw drive pair consists of a screw and a screw nut matched with the screw. A permanent magnet is spirally arranged on the screw to cause magnetic fields along a spiral line on the screw to be uniformly distributed, and to cause magnetic fields along a side direction and a normal direction of the spiral line on the screw to be non-uniformly distributed, so as to form a spiral permanent magnetic track; and the screw nut refers to a high temperature superconductive screw nut, which is provided with a high temperature superconductor with a seed crystal face directing to a radial direction of an inner hole of the screw nut. The device has the advantages of eliminations of mechanical friction and abrasion, noise reduction, high drive efficiency and long service life.

A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system

Abstract: Thrust measurements were performed on a coil made of YBa2Cu3O7-d coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of I_DC=30 A for the superconducting coil and alternating current of I_AC=9 A for the stator coils, thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back plate, thrust was increased by 70%.