Electromagnetic Waves in Transformer Coils Treated by Maxwell's Equations

Abstract

A rigorous solution of Maxwell's equations is derived for waves in a thin single-layer coil, a concentric ground electrode being at a short distance from the coil. Simple transformer coils resemble such an ideal to a considerable degree. Any electromagnetic state of the coil propagates slowly in axial direction with such a velocity that the phase velocity along the helical conductor equals the velocity of light. The surge impedance of the coil is constant for low frequency, but decreases with higher frequency, the boundary wave-length being determined by the insulating distances.