Capacitive coupling through a hydrodynamic journal bearing to power rotating electrical loads without contact

Abstract

A capacitive power coupler has been devised using a hydrodynamic journal bearing assembly that facilitates sufficient coupling for kilowatt-scale non-contact power transfer to a rotating load. The capacitive coupler, combined with associated driving circuitry, is an efficient low maintenance solution for powering a variety of rotating or pivoting electrical loads in machines and automation. A hydrodynamic journal bearing capacitor assembly utilizing an ultra-thin cushion of lubricant as dielectric between concentric capacitor electrodes is presented. Hydrodynamic operation ensures high coupling capacitance, ease of manufacturability and eliminates brush and slip ring maintenance. The system's small size, weight, and simplicity are competitive with contemporary inductive wireless power transfer methods in this small gap application. Experimental results for a ~5nF prototype coupler operating at 840 kHz are presented.