Dielectric Hysteresis at Radio Frequencies

The development of a transformer for 100,000 volts at 100,000 cycles is described in detail. The successful construction is given. The necessary even potential gradient along the high tension secondary of the transformer is provided by special end shields. The dielectric strength of air is determined at radio frequencies, and the novel behavior of air at these frequencies is described. The methods of measurement of dielectric losses of various materials are given. The materials tested show that the predominant loss is constant per cycle (i.e., it gives rise to a constant power factor). Mica, glass and paper show also a slight equivalent series resistance (corresponding to a power factor increasing with the frequency); asbestos a shunt resistance. The break-down conditions of the various dielectrics were studied. The dielectric hysteresis of air is measured, and it is found that radio frequency corona as well as arc-over distance are subject to the same laws as at audio frequencies.