Measurements of Coupling Time Constants and Geometry Factors of Coupling Losses in Spiral Copper-Plated Multifilament Coated Conductors

Spiral geometry is effective to reduce coupling time constants of copper-plated multifilament coated conductors. We wound copper-plated multifilament coated conductors with various specifications spirally on round cores, and measured their magnetization losses in a wide range of frequency to determine their coupling time constants as well as the geometry factors of coupling losses. The core diameter was decreased down to 2.5 mm in order to show the feasibility of such conductors with reasonably high overall current density. The influence of various conductor parameters such as copper thickness, conductor width, and number of striations (filament width) as well as core diameter on coupling time constants and geometry factors were studied. By using the obtained coupling time constants and geometry factors, we calculated coupling losses of various conductors, whereas we calculated their hysteresis losses by using Brandt and Indenbom's formulae. These calculated hysteresis losses and coupling losses were compared with measured magnetization losses for various conductors.