Qunxu Lin

Method to reduce levitation force decay of the bulk HTSC above the NdFeB guideway due to lateral movement

A magnetic levitation vehicle using bulk high-Tc superconductors (HTSC) is considered as a promising transportation type thanks to its lateral inherent stability, but previous studies have found that the levitation force (LF) decays due to lateral movement. In this paper, a pre-load method is presented to reduce the LF decay, and the experimental results indicate that this method is very applicable in supressing this decay in spite of the applied field and material property of the bulk HTSC, and this effect can be ascribed to the reduction of the hysteresis loss in the bulk HTSC, i.e. more trapped magnetic flux after the pre-load case. In the end, experimental results indicate that the Halbach PMG has an advantage to reduce the cost of the PMG, but its rate of LF decay is also larger due to lateral movement

A High-Temperature Superconducting Maglev Ring Test Line Developed in Chengdu, China

A 45-m-long high-temperature superconducting (HTS) Maglev ring test line, named “Super-Maglev,” has been successfully developed in Chengdu, China, in February 2013, 12 years after the birth of the first man-loading HTS Maglev test vehicle. The Maglev vehicle (2.2 m in length, 1.1 m in width) is designed for one passenger with a levitation height of 10–20 mm; the permanent-magnet guideway (PMG) (45 m in length, 0.77 m of track gauge) is a racetrack shape with a curve radius of 6 m; the driving is accomplished by a linear induction motor with a maximum running speed of 50 km/h. The linear motor is composed of four submotors installed at one straight section in the middle of the double PMGs, and the total length is 3 m. This second-generation HTS Maglev vehicle system is highlighted by the cost-performance and the wireless multiparameter onboard monitoring function. The current same-level load capability has been achieved over a small-section low-cost PMG whose cross-sectional area is only 3000 mm2. On the vehicle, parameters of levitation weight, levitation height, running speed, acceleration, lateral offset, online position, and total running distance of the vehicle are real-time monitored and displayed on the onboard tablet computer. The system component and test data are reported in detail in this paper.

Maglev performance of a double-layer bulk high temperature superconductor above a permanent magnet guideway

In order to improve the performance of the present high temperature superconducting (HTS) maglev vehicle system, the maglev performance of single- and double-layer bulk high temperature superconductors (HTSC) was investigated above a permanent magnet guideway (PMG). It is found that the maglev performance of a double-layer bulk HTSC is not a simple addition of each layers levitation and guidance force. Moreover, the applied magnetic field at the position of the upper layer bulk HTSC is not completely shielded by the lower layer bulk HTSC either. 53.5% of the levitation force and 27.5% of the guidance force of the upper layer bulk HTSC are excited in the double-layer bulk HTSC arrangement in the applied field-cooling condition and working gap, bringing a corresponding improvement of 16.9% and 8.8% to the conventional single-layer bulk HTSC. The present research implies that the cost performance of upper layer bulk HTSC is a little low for the whole HTS maglev system.

Superconducting Excitation System of a Small Scale Linear Synchronous Motor

A four pole superconducting excitation system that was part of a linear synchronous motor (LSM) system, was fabricated and its thrust and normal forces studied experimentally. Four cases were investigated, air-cored, with a ferromagnetic (FM) back plate, an FM core, and with both an FM back plate and core. With a total of only 15 m of YBCO coated conductor in the form of four coils as the excitation system, thrust output of up to 95 N while operating at 77 K with a magnetic gap of 10 mm was obtained in one particular case. The results of the studied superconducting LSM system help better understand the feasibility of their applications to drive systems for Maglev trains.

Performance of a Small-Scale High Temperature Superconducting Linear Synchronous Motor Prototype

Four coils made of YBCO-coated conductor wire were fabricated and connected in series to make up the excitation system of a linear synchronous motor system with a stator made of ordinary copper wire. The electromagnetic forces experienced by the superconducting coils with respect to the stator were studied in the static case. We began with the study of one single coil, followed by two coils connected in series, and finally, four coils in series from which the largest force obtained was of 53.9 N at a gap of 10 mm at 77 K. The critical current, n-value, and inductance were also measured for the coils so that the power dissipation of the field windings can be calculated. This paper also helps us understand whether linear motors with superconducting components are currently economically feasible with present commercially available superconducting wire.

Research of Radial High Temperature Superconducting Magnetic Bearings for Cryogenic Liquid Pumps

The mechanical bearing in the cryogenic liquid pump has short working life due to the low temperature environment. For conquering the disadvantage, the radial high temperature superconducting magnetic bearing (HTSB) is designed to be used in the cryogenic pump. The high temperature superconductors (HTSs) in the HTSB are cooled by the cryogenic liquid directly. The introduced cryogenic liquid pump can constrain the heat leakage. The equipment for the kinetic characteristics of the HTSB is introduced, and it can measure the axial forces of the HTS at different rotation speeds. Basic mechanical principle of the rotor of the pump is analyzed.

Hydrostatic Pressure Effects on the Critical Current of YBCO Coated Conductor Wire

The critical current density of optimally doped bulk YBCO superconductor has been found to increase with the application of external hydrostatic pressure. This paper reports the transport measurements of the critical current (Ic) of YBCO in the form of a coated conductor (CC) wire under hydrostatic pressure up to 0.24 GPa at 77 K. No noticeable change was observed in both the Ic and n-value of the CC sample in the studied pressure range. Two possible scenarios are discussed to explain the observed effect.

Experimental Study of the Electromagnetic Forces of a HTS Bulk Magnet Subjected to Sinusoidal Traveling Magnetic Field

High temperature superconducting (HTS) bulk sample acts as quasi-permanent magnet when it traps magnetic field, and the superconducting bulk magnet can substitute the traditional permanent magnet in the engineering of the linear motor for the purpose of achieving higher efficiency. The electromagnetic forces between the HTS bulk magnets and the ac magnetic field are the most important parameters to consider for the engineering of a motor. We measured the static vertical and thrust forces of an HTS magnet subject to a sinusoidal traveling magnetic field at different trapped fields and at different current amplitude and frequencies. The force relaxation of the HTS bulk magnet was also compared with that of a traditional permanent magnet. The feasibility of replacing the conventional magnet in the ac application machines by HTS bulk ones was preliminary validated experimentally.

Influence of Auxiliary Permanent Magnet on the High-

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.

T_{\rm c}

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.