An EHV current transducer with feedback-controlled encoding

There exists substantial interest to produce a low-cost high-performance solid-state EHV current transducer possessing both compactness and low complexity. A number of incentives have not only prompted in the past, but are responsible for current research and development effort throughout the world. In general, these incentives encompass both the limiting cost of conventional means at high voltage and the much desired interfacing advantages to be realized with modern solid-state systems. An optically isolated system utilizing a novel electronic modulation scheme will be described. The approach is realized through a feedback-controlled encoding system. This technique performs a comparison between the actual current being monitored and its encoded representation. Differences resulting from components or circuitry drift, for example, are automatically corrected on a continuous basis. This feedback approach, therefore, permits substantial reduction in both component specification and circuit complexity while providing excellent linearity and accuracy. The resultant high-performance system possesses both simplicity in design and decidedly advantageous interfacing properties with solid-state controls at, or below, EHV levels.