Influence of Cable and Twist Pitch Interactions on Eddy Currents In Multifilamentary Strands Calculated Using an Anisotropic Continuum Model

Abstract

We have calculated the eddy current loss in multifilamentary strands wound into helical geometries (round cable geometry) as a function of the cable pitch (L_cab) twist pitch (L_p), and cable radius (R_c). Previous calculations of this interaction concentrated on modifications of the mutual inductance, finding a loss minimum at L_cab = L_p. However, our calculations show that the effective coupling lengths will be enhanced near L_p = L_eff (≈ L_cab for L_cab < < 2πR_c), an effect similar to the interactions between spatial field variation and L_cab found to occur in cables (where both mutual inductance and geometrical factors where considered). We have calculated the loss for single multifilamentary strands wound into helices in order to simulate the geometrical effects of cabling. It is found that if L_cab < < 2πR_c (the helix or cable radius), losses peak when L_p ≈ 2πR_c, independent of the relative helicity of L_p and L_cab. If, however, L_cab > > 2πR_c, the loss maximum occurs for L_p ≈ L_cab, only if L_p and L_cab are of opposite helicity.