The Low Frequency Magnetic Field Susceptibility Characteristics of Advanced Marine Cables and a Comparison with Several Equivalent MIL-C-915 Cables

The electromagnetic compatibility (EMC) of electri­ cal and electronic equipment that are located in the below-decks areas of Naval ships is greatly deter­ mined by the emission and susceptibility character­ istics of their cables and the method in which these cables are run. The concern for protection against a nuclear electromagnetic pulse (EMP) and the desire to reduce the tremendous weight of shipboard cables has led to the development of the advanced marine cable (AMC). This cable is also referred to as the lightweight cable due to its thinner insulation and its single optimized braided [1] shield. Since a handbook [2] has already been developed to ensure the magnetic field compatibility of all below-deck cable installations, it became necessary to theoretically verify the electromagnetic inter­ ference (EMI) characteristics of these new cables. The incorporation of these cables into the handbook would facilitate their usage without compromising shipboard EMC. Utilizing cable data for the 233 cables, which was provided by one AMC cable manufacturer, the cables pitch diameter, pitch distance (lay length), and effective loop area (ELA) were calculated. Eight samples of various AMC cables were then tested utilizing a Helmholtz coil and a narrowband spectrum analyzer to determine their magnetic field suscept­ ibility. A comparison was made with a selected number of MIL-C-915 cables to illustrate that, although the AMC cable typically has a reduced magnetic field susceptibility (due to its typically smaller ELA), its variable lay technique, designed to reduce high frequency crosstalk on many AMC cables, can actually make them more susceptible to low-frequency magnetic field pickup.