Ground fault detector for high-voltage DC power supplies.

摘要

To detect a ground fault, the alternating current leakage current to common AC electrical ground is sensed across a resistor and applied to one input of an analog gate. The analog gate is opened by the positive going voltage from the high-voltage secondary of the power supply transformers between 7 degrees from the crossover point and 103 degrees to pass only that portion of the potential representing the alternating current leakage current which is in phase with the potential on the secondary windings of the power supply transformer and thus provide a signal representing the real component of the AC impedance to ground. A reference level is set by applying a current adjusted for voltage variations of the power supply and the range of the power supply through a potentiometer, with a tap on the potentiometer providing a preset level of impedance, below which a ground fault is indicated. The preset level of impedance and the signal from the gate are applied to a comparator so that an output signal is provided whenever the real component of the AC leakage current exceeds the preset value.