Transfer impedance of nonmagnetic conduits of various shapes

Metallic conduits provide mechanical support for cables, and may also protect the cables against interference caused by currents induced by external electromagnetic fields. The conduit transfer impedance Z/sub t/ then is a good measure for the provided protection. We studied Z/sub t/ by means of conformal transformations and of the method of moments in a quasistatic, two-dimensional (2-D) approach. Practical U-, H-, L-, and T-shaped conduits are discussed. Conformal transformations provide simple engineering expressions for the mutual inductance part of Z/sub t/ for cable positions inside the conduit. The method of moments formulation results in useful approximations for the crossover frequencies in Z/sub t/ between DC and high frequency. Measurements on U-shaped conduits confirm the calculations.

[1]  H. Kober,et al.  Dictionary of conformal representations , 1957 .

[2]  Sir Charles Darwin F.R.S..  I. Some conformed transformations involving elliptic functions , 1950 .

[3]  A.P.J. van Deursen,et al.  The transfer impedance of cables with a nearby return conductor and a noncentral inner conductor , 1995 .

[4]  A.P. Sakis Meliopoulous,et al.  Performance evaluation of steel conduit enclosed power systems , 1996, IAS '96. Conference Record of the 1996 IEEE Industry Applications Conference Thirty-First IAS Annual Meeting.

[5]  A.P.J. van Deursen,et al.  Protection of cables by grounding structures , 2000 .

[6]  S. A. Schelkunoff,et al.  The electromagnetic theory of coaxial transmission lines and cylindrical shields , 1934 .

[7]  H. Kaden.  Wirbelströme und Schirmung in der Nachrichtentechnik , 1959 .

[8]  van Mjam Mark Helvoort.  Grounding structures for the EMC-protection of cabling and wiring , 1995 .

[9]  Paul F. Byrd,et al.  Handbook of elliptic integrals for engineers and scientists , 1971 .

[10]  Roger F. Harrington,et al.  Field computation by moment methods , 1968 .

[11]  Irene A. Stegun,et al.  Handbook of Mathematical Functions. , 1966 .

[12]  A.P.J. van Deursen,et al.  Reliable protection of electronics against lightning: some practical applications , 1998 .

[13]  S. Marshall.  A rapidly convergent modified Green' function for Laplace' equation in a rectangular region , 1999, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[14]  van Ma Rinus Houten.  Electromagnetic compatibility in high-voltage engineering , 1990 .

[15]  D. F. Lawden.  Elliptic Functions and Applications , 1989 .

[16]  P. Laan,et al.  Coupling on a multilayer printed circuit board and the current distribution in the ground plane , 1996 .