HTS synchronous generators, in which the rotor coils are wound from high-Tc superconducting wire, exciting attention due to their potential deliver very high torque and power densities. However, injection of large DC currents required by presents a technical challenge. In this paper we discuss development brushless exciter operates across cryostat wall inject current into coil circuit. This approach fundamentally alters thermal load upon cryogenic system removing need for thermally...

We present a No-Insulation (NI) Multi-Width (MW) winding technique for an HTS (high temperature superconductor) magnet consisting of double-pancake (DP) coils. The NI enables self-protecting and the MW minimizes detrimental anisotropy in current-carrying capacity tape by assigning tapes multiple widths to DP coils within stack, widest top bottom sections narrowest midplane section. This paper presents fabrication test results NI-MW demonstrates unique features technique: enhanced field...

REBCO coated conductors are now being used for building very high-field magnets with large electromagnetic stresses, both expected ones due to transport current × stresses and additional resulting from the screening currents inherent in wide tapes. Post mortem analyses of several recent test coils operated above 40 T show that significant conductor plastic deformation occurs, even JBR well below ∼1 GPa yield Hastelloy substrate conductor. To investigate these mechanisms, were unwound after...

A no-insulation (NI) pancake coil was wound with a 23 m long REBCO tape containing multiple 'defects', at which local critical currents are substantially lower (<80%) than the tape's lengthwise average. During charging test up to 60 in bath of liquid nitrogen 77 K, showed 'defect-irrelevant' behaviors, i.e. terminal voltages and center fields steady-state operations were barely discernible from those an ideal 'defect-free' coil. Also, current (Ic) measured be 68 A, close 72 estimated Ic...

Present research on no-insulation (NI) rare earth barium copper oxide (REBCO) magnets have demonstrated their ability to produce high fields due compact nature. NI often been be self-protecting. However, evidence of mechanical damage in recent field magnets, suggests that there are some issues about quench must resolved for this otherwise promising technology. This article attempts explain multi-physics phenomena occurring during the an magnet can used elucidate behavior through experiments...

Recently, gearless type generators, which have very low rotation speed and high torque, been preferred over the geared due to problem of gearbox reliability. In particular, a high-temperature superconducting generator is promising for wind power applications because its advantages weight, size, efficiency. this paper, 10-MW class designed using Y-Ba-Cu-O Bi-Sr-Ca-Cu-O wires, weight estimated. The finite elements method used analyze magnetic field distribution, 3-D CAD program calculate...

Here we report the effect of field-dependent index value <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n(B,\theta)$</tex-math></inline-formula> on screening current and consequential NI REBCO coil behavior. Through ‘Little Big Coil (LBC)’ framework, an unexpected voltage behavior has been observed at top bottom coils in fourth mini magnet LBC4 during self-field operation 77 K. The measurement demonstrates...

In general, conventional induction heating system is designed only for a specific metal billet or object, because the should be specialized to guarantee best performance regarding quality and efficiency. It has been applied large systems in metallic processing industries. A DC method using HTS magnets can one of better counterplans higher efficiency multi-purpose system. this paper, we evaluated 10 kW-class machine without additional function equipment, performed analysis on various metals,...

This paper presents a design of 35 T 40 mm winding diameter no-insulation standalone magnet that consists stack 52 double pancake (DP) coils wound with multi-width REBCO tapes. The inner and outer diameters height the are mm, 221.6 628 respectively. It is designed to generate at an operating current (I op) 179.8 A in bath liquid helium 4.2 K. All DP will be 'dry' without epoxy, making turns within essentially 'self-supporting,' which effective reduce magnetic stress. To charging time...

A single pancake no-insulation (NI) coil was wound in a hermetic way with REBCO tape having thin (1–2 μm) cladding layer of stainless steel. With an electric heater embedded at the innermost turn coil, heater-induced quench tests were performed under background field 15 T bath liquid helium 4.2 K. Despite large average contact surface resistance 1.63 cm2 times larger than those pure NI coils, 'thermal recovery' observed current density (Je) below 700 mm−2 mainly due to local sharing. The...

Abstract Recent reports on screening current stress simulations of high-field REBCO magnets frequently present peak stresses over 1 GPa. However, this result is probably an unrealistic artifact purely elastic calculations, considering the macroscopic yield and fracture approximately 900 MPa less than 1.1 GPa for Hastelloy substrate-coated conductors. Here, we evaluate elastic-plastic conductor damage at 0.4% strain using a high-stress coil exposed to high field explore regime. The was...

This paper describes and discusses a No-Insulation (NI) winding technique that, based on experiment results of two test NbTi coils, promises to significantly improve stability ease protection high performance magnets; if applied those used in marketplace MRI magnets, it may eradicate premature quenches that still afflict these though much less frequently than the past. The key idea is single turn an NI can, upon quench, share copper stabilizers neighboring turns through turn-to-turn...

In this paper we summarize what have learned so far and discuss key technical challenges that face the HTS “NI” magnet wound with no-insulation (NI) technique, focusing one of its beneficial features, self-protecting. We first describe basic features NI winding including lumped circuit distributed network models. Next, present results a stand-alone composed REBCO double-pancake coils, showing is indeed selfprotecting. last part paper, issues, often called “NI behaviors”, objectionable...

This paper presents a “combined” circuit model to simulate non-linear behaviors of no-insulation (NI) high temperature superconductor (HTS) coil. The key idea is selective use either the lumped or distributed depending on an operating condition. When NI coil current below its critical current, radial leak currents through turn-to-turn contacts may be assumed uniformly over entire coil, thus, suffice analyze behaviors. increases beyond plays role spatial distribution currents, both and...

Since the screening current induced in rare earth-barium-copper-oxide (REBCO) magnet generates an irregular magnetic field, a few simulation methods have been proposed. For insert REBCO generating ultra-high new method has proposed with consideration of coil-deformation effect. In this article, we developed based on partial element equivalent circuit (PEEC) model coupling two-dimensional stress finite analysis to accurately time-transient distribution accurate current. presented method,...

No-insulation (NI) rare-earth barium copper oxide (REBCO) magnets are promising for high field or temperature superconducting because they simplify quench protection. However, the turn-to-turn leakage current path induced by absence of insulation introduces nonlinearities into magnetic fieldcurrent characteristic and significant delay in reaching desired field. This paper shows that active feedback control can mitigate both nonlinearity charging delay. To verify our approach, simulations...

This paper considers the insulationless high-temperature superconducting (HTS) magnet as a new and innovative concept for dc applications due to its benefits compared conventional HTS magnets with insulation layers between conductors. The purpose of this is study operating characteristics an magnet. normal were investigated according various current levels. Thermal stability was also analyzed. critical measured at 40 K. temperature distribution using thermocouples. experiment results...

This paper presents a system for real-time monitoring spatial and temporal electromagnetic behaviors of high temperature superconductor (HTS) coil with the no-insulation (NI) winding technique. We implemented that consists Hall sensors voltage taps to measure magnetic fields, local voltages. An NI HTS test was wound, combined coil. experimental study performed in liquid nitrogen bath at 77 K, where charged constant ramp rate 0.05 As <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...