A new AC–DC transfer device for high voltages and high frequencies using electrooptic modulation

AC-DC transfer is performed almost exclusively using thermal converters. At voltages above a few volts, series resistors are used to extend the permissible voltage, which leads to significant power being drained from the source. By contrast, sensing the electrical field in a suitable electrode system by utilizing the Pockels effect of an electrooptic crystal will draw just a small, almost only capacitive current. The impact of the Pockels effect is analyzed by detecting the rotation of the polarization of a light beam by means of an analyzing polarizer and a photo detector. By setting the right operating point, a square law relation between the applied electrical field strength or voltage and the detector output can be obtained. This allows a traditional AC-DC transfer to take place using the same measurement setup and algorithms as common for thermal converters. Due to the low power dissipated in the device, high voltages at high frequencies can be measured.