Charles B. Arends

The Short-Circuit Rating of Thin Metal Tape Cable Shields

It is pointed out that conventional methods of calculating the short-circuit ratings of cable conductors can lead to gross errors in the case of the thin metal tape shields commonly used in plastic-insulated cables. A more rigorous treatment of the problem is developed for both single and repeated short circuits. The theoretical calculations are compared with the results of a series of practical tests on two types of 15-kV polyethylene-insulated cable and with other test data available to the authors. Substantial agreement is found.

All-polymeric infrared reflecting films

Coextruded multilayer films consisting of 657 layers of three different polymers have been made which reflect near infrared wavelengths while transmitting visible light. A repeating multilayer stack of the three polymers in layer sequence A/B/C/B with optical thickness ratios of 2/1/2/1 suppress second through fourth order reflectance when refractive indices of the polymers are chosen so that nB = (nAnC)11/2. Broadband reflectance of solar infrared can be obtained by imposing a layer thickness gradient through the crossection of the film. Compared to conventional vacuum deposited multilayer interference stacks, all-polymeric films can be tough and thermoformable. They do not corrode and there is no metal waste. Potential applications include solar energy management. Multilayer film design, polymer specification and coextrusion of initial films to demonstrate feasibility are described.