A novel converter topology for TEM applications

Abstract

Time-domain Electro Magnetic (TEM) systems, are used for remote sensing of conductive mineral deposits buried under the surface of the earth. A low frequency trapezoidal current excitation set-up in an exciter coil loop causes a flux that penetrates deep into the earth. When the excitation is cut off sharply, conductive deposits in the earth carrying flux react by causing eddy current flows within them. The flux produced by such eddy currents is picked up by a sensor coil. By comparing the emf induced in the sensor coil with a priori known emf patterns for mineral deposits, the presence of mineral deposits can be ascertained. The voltage, current and energy levels of the TEM system, require special type of excitation technique. Power converters for such non-standard requirements are not reported in the literature, particularly for TEM applications. This paper introduces TEM systems to the reader and presents the requirements for excitation. A converter topology to meet the requirements, it's analysis, control and performance are presented. Among other alternatives that the authors have attempted, the topology presented features reduced number of passive elements, high voltage gain and low losses. These features enable the sensor head to be operated from the normal low level battery.