Giant-Magnetoresistance-Based Galvanically Isolated Voltage and Current Measurements

Nowadays, dc current is much more widely used than a decade ago, not only in the well-known high-voltage dc transmission but also as dc-powered marine systems, dc data centers, and dc fast charging systems for electric vehicles. However, galvanically isolated dc voltage or current sensors are, in terms of accuracy, noise level, or dimensions, still far behind the ac measurement devices in low and medium voltage areas. In this paper, a giant-magnetoresistive-based sensor system for galvanic isolated dc current and voltage measurements is introduced. The system mainly consists of a special coil arrangement with low inductance for voltage measurement, a special U-turn for current measurement, and A/D converters with a low-cost field-programmable gate array for signal conditioning. The sensor system showed an outstanding measurement accuracy of 0.3% for voltage values up to ±550 V and 0.2% for current values up to ±100 A in a temperature range from -30 °C to 90 °C. This completely new approach for the galvanically isolated measurement of electric voltage and current avoids the use of bulky magnetic components and expensive power-consuming analog electronics, which allows one to integrate it in the current ac measure unit for power monitoring.