Tape-wound Coils Research Articles

Computing Strains Due to Screening Currents in REBCO Magnets

Screening currents have long been known to impact the stress state in tape-wound superconducting coils. In recent years the advent of REBCO tape has led to the development of tape-wound coils by a number of organizations. While several groups have been computing screening currents and ac losses in REBCO tape in a variety of applications for several years, little has been published about the stress due to the screening currents. This problem is challenging due to the need to analyze thousands of REBCO turns which are not bonded together. The T-A formulation of Maxwell's equations employing a homogenization technique enables efficient estimation of the current distribution while structural calculations employing contact elements allow conservative estimation of stresses. Computational results are compared with observed degradation in a test coil. Future coil designs that include the effects of screening current strains are proposed.

The analysis of stray losses in tape wound concentrated windings of the permanent magnet synchronous motor

Purpose – The purpose of this paper is to analyse the stray losses in the windings of permanent magnet synchronous machines (PMSM). Design/methodology/approach – The 2D field model, based on the edge element method (EEM) and A -V formulation, has been developed and utilized for the determination and analysis of stray losses in the PMSM with concentrated windings made of strip conductors. The influence of the supply frequency as well as the slot opening width on the losses caused by eddy currents has been examined. The different arrangements of the conductors in the tape wound coils have been studied. The obtained results have been compared to the reference case when the eddy current effect is neglected. Findings – The usefulness of the proposed methodology of the stray losses evaluation has been tested on the case study problem. It has been observed that the stray losses in the windings of the considered machine can be reduced by choosing the proper value of the slot opening. The dependence of the stray l...

A new wideband common-mode noise filter consisting of Mn-Zn ferrite core and copper/polyimide tape wound coil

A new wideband common-mode noise filter for switching power supplies has been developed. The filter consisted of an Mn-Zn ferrite core and a copper/polyimide tape wound coil. The tape wound coil had two signal lines, two ground lines, and a polyimide dielectric film. The filter exhibited a common-mode rejection of over 30 dB in the wide frequency range of 100 kHz to 100 MHz. The wideband common-mode filtering was due to the high-frequency magnetic loss of the Mn-Zn ferrite core and the optimum ground point selection for the ground lines.

The design for a high-Tc superconducting magnetic separator

A number of options for the design of a superconducting high-Tc magnetic separator have been considered and it is suggested that, when material properties have improved sufficiently, a separator based on a flux tube with a flux pump will offer significant advantages. Another design for a more detailed evaluation was chosen based on an iron magnetic circuit in which amper-turns were supplied by a superconducting BSCCO-Ag tape wound coil operating at 77 K. Two configurations for the separator were considered, a ball matrix separator and a wire matrix high-gradient separator. Practical separations will be possible with such a system.

Magnetic system of the GOL-3 installation

The magnetic system of the GOLD-3 device for studies of plasma heating by high-power relativistic electron beams is described. The main part of the magnetic system is a pulse solenoid with a total length of 7 m and an inner diameter of 15.7 cm. The solenoid consists of 60 multi-turn tape-wound coils. The selenoid magnetic field in the operating regime is 6 T and the maximum achievable magnetic field is 11 T.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Critical Temperature of Some Persistent Nb3Sn Coils

The critical conditions for several 14-cm-i.d., 2.5-cm-long Nb3Sn tape-wound coils was determined by increasing the temperature at constant current. The coils are inductively energized and have no external electrical leads. At lower temperatures, some of the critical temperatures are well below the ``short-sample.'' Some data for coils energized in a gaseous helium environment instead of in a liquid-helium environment are included. The implications of these results for design of levitated superconducting coils for plasma physics experiments is discussed.

A Novel Technique for Pulsing a High Magnetic Field

Radar modulator techniques, which make use of pulse-forming networks (PFN), were used to develop a magnet pulser which supplies 500-amp current pulses to a 20-turn tape-wound coil for generating a pulsed, high magnetic field. Uniform fields of more than 5 kilogauss were generated with pulse widths of 6 to 14 ?sec at repetition rates up to 1200 Hz. New cooling techniques for the load coil and the pulser components are being developed so that higher fields at higher repetition rates can be generated.

Tape-wound magnet coils

A tape-wound coil capable of high power density and of design suitable for application to large magnets is described. The water-cooled coil of moderate size, 6 × 16 × 16 in. attained a power density of 16 900 W per pound of copper. The coil was wound with copper tapes separated by spacers to allow cooling water to pass axially through the coil. Detailed description of the conductor and fabrication is given. Discussion of maximum current density, magnet pressure, leakage currents and monitoring is also presented.

Flux Concentrator for High-Intensity Pulsed Magnetic Fields

Use of multiturn coil structure in the production of several hundred kilogauss pulsed fields is discussed with specific emphasis on coil life. The magnetic force that shortens the coil life is reduced by introducing a flux concentration device. Into the multiturn coil is inserted a rigid, slotted metal slug that generates induction current in such a way as to shift the magnetic flux from the multiturn to the central vacuum region and serves as a flux concentrator. Electromagnetically and mechanically this scheme is a convenient synthesis of the multiturn and single turn coils. The advantage of this scheme is most apparent for tape-wound coil structures, and a quantitative analysis of the flux pattern relevant to this coil system is given. An analog computer is employed in solving the time dependence of the field. The results are documented by experimental tests carried out with a 3000-μf, 4-kv capacitor bank.