Cable Trays in EMC: Measurement and Modeling to 30 MHz

Common mode (CM) currents are a major source of interference in electrical and electronic systems. Cable trays are often used to shield cables from unwanted CM electromagnetic interference, and their shielding characteristics are defined in terms of transfer impedance. We present the measurement and modeling of nonmagnetic U-shaped cable trays from 300 kHz to 30 MHz. A calibrated vector network analyzer in a screened environment is required for the high dynamic range measurements. We use method of moments simulations to determine the transfer impedance and mutual inductance within the interior region of a cable tray. We refined the modeling after detailed attention to the code. The computational and measured data are in good agreement. We propose the simulation as a means to predict the magnetic fields, mutual inductance, and transfer impedance associated with victim cable loops in the cross section of nonmagnetic cable trays to frequencies well beyond our studied range of 30 MHz.