Jointless Pancake Coil Winding for Minimizing Electrical Loss in HTS SMES for Wind Power

Abstract

Many different applications of superconducting devices have been designed using a modular pancake arrangement. It has been reported that this modular pancake structure provides excellent mechanical holding, effective cooling, and high magnetic flux density for stability of the superconducting coil. However, soldering for interconnecting each double pancake causes current decay, cryogenic coolant loss, and thermal stress. Thus, this research investigates an improved double pancake winding, named the 'Jointless Double Pancake Coil Winding' and demonstrates the efficacy for minimizing the electrical loss of the High Temperature Superconducting (HTS) coil, assembled in the modular double pancake types. It presents a winding method that avoids soldering between the pancake connections, and thus removes the primary cause of the electrical loss generated in the existing design. This proposed winding method can effectively achieve zero electrical loss. This paper particularly presents the application of the proposed winding for the HTS-SMES and demonstrates the feasibility and improved functional benefits with reference to the conventional coil. This research should maximize the operational benefits of using the SMES coil employing the proposed winding method in charge and discharge operations, and should increase the effectiveness and efficiency in cryogenic system.

Intermittent Smoothing Approaches for Wind Power Output: A Review

“…Furthermore, SMES coils are fabricated with bridge joints, which cause loss in the form of Joule heat. A refined double pancake winding also known as "jointless double pancake coil winding" has been proposed to minimize the electrical losses due to high-temperature superconducting SMES coils [93].…”

“…However, they require high expenditures due to the need for a cryogenic system to keep the superconducting coil within the superconducting state [92,93].…”

High-temperature superconducting undulator magnets

“…Because of their tape-shaped geometry, 2G-HTS do not tolerate significant side-bending, and this traditional approach of coil-winding is not feasible. Instead, HTS magnets are typically wound as pancake coils in which the tape is wound on itself from the inside out to the desired outer diameter of the magnet [20,21]. The connection between pancake coils is made through resistive bridge joints, and, depending on the coil geometry, there is one joint for every pancake coil [9,20] or for every two pancake coils [11,21].…”

“…Instead, HTS magnets are typically wound as pancake coils in which the tape is wound on itself from the inside out to the desired outer diameter of the magnet [20,21]. The connection between pancake coils is made through resistive bridge joints, and, depending on the coil geometry, there is one joint for every pancake coil [9,20] or for every two pancake coils [11,21]. Although resistivity values as low as 35 nΩ cm 2 can be routinely made for a double lap joint [11], the high operating current of the order of 1000 A and the large number of joints incur a substantial heat load.…”

Feasibility and electromagnetic analysis of a REBCO superconducting undulator

“…The main obstacle, here, is that the tape-geometry of 2G-HTS CCs precludes side-bending and therefore the conventional layerby-layer coil winding does not work. Instead, the tape is wound onto itself resulting in racetrack windings [12,16,17]. A particular feature of undulator magnets is that the current direction reverses between successive racetrack windings such as to generate the oscillatory on-axis field (see figure 1).…”