Impedance Fault Detector Circuit
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
An impedance fault detector circuit checks that the voltage across a load is compatible with the current in the load knowing the value of the impedance. A current is produced proportional to voltage across the load, and another current is generated proportional to load current. Components are selected so that under normal conditions the two currents are equal. Current inequality is detected by a window detector which responds with a signal if the inequality exceeds a predetermined value. As shown in the circuit design, a power bridge switches current into a floating inductive load, e.g., a motor. Initially, assume that the impedance is purely resistive. The voltages at either end of the load are converted to current by equal resistors R1 and R2 .R1 .