DETERMINATION OF SELF AND MUTUAL INDUCTANCES OF A DOUBLE-HELIX COIL

Jaroslav Franek – Mojmír Kollár

   This paper is concerned with determination of self and mutual inductances in two cases of a double-helical coils with accordingly (spiral) or oppositely (anti-spiral) twisted wires. The former of these instances is the twisted-pair lead (TPL) pair, here described as a spiral double-helix. Parametric description of appropriate line integral is used to determine the inductance per unit length by evaluating the vector potential integral along the edge of the twisted conductors. As a variable parameter the twist-angle or the number of the turns per unit length (turning rate) is introduced. There are two limit cases of this task. The first, with zero twist-angle, will lead to a well known two-wire or twin-lead (transmission) line. The second, with relatively high "turning rate" is approaching to case of a long solenoidal coil.

Keywords: double-helix coil, twisted pair lead (TPL), twin lead, numeric solution, magnetic field, per-unit-length inductance

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