Study on optimal thickness of copper layer of REBCO-coated wire for quench protection

Abstract

The most probable cause of quench damage of REBCO coated wire is localized over-heating at a hot-spot in the coil wire during the quench protection sequence. To reduce the hot-spot temperature, it is effective to increase the thickness of the Cu layer of the coated wire. However, the thick Cu layer deteriorates the overall current density of the wire. The wire with thin Cu layer may be damaged by a quench at low operational current. For a coil of a real application it is important to increase the current density of the winding pack of the coil at operating condition. Increase of the overall current of the wire itself by reducing thickness of the Cu layer is not necessarily to increase the winding pack current density considering quench protection. In the paper, the optimum value of the thickness of the Cu layer is analytically studied based on a thermal model of the winding pack to maximize the winding pack current density, while the coil is safe from the damage caused by quench.