Circuit for monitoring the inductance of an inductive load to indicate occurrence of a fault

摘要

A circuit for monitoring the inductance of an inductive load controlled by phase-operated thyristor devices or similar devices. One embodiment of the invention comprises a first current sensitive device to produce a signal proportional to the current flowing through the load, a voltage sensitive device to produce a signal proportional to the voltage across the load, an inductor driven by the voltage signal and a second current sensitive device for producing a signal proportional to the current flowing through the inductor. The first current signal is then rectified and fed to a voltage divider consisting of five series connected resistors. The second current signal is also rectified and fed to the same voltage divider. A comparator is connected to the aforementioned voltage divider and senses any voltage change on the voltage divider due to a change in the ratio of the second current signal to the first current signal (or the inverse ratio) and thus in effect, senses any change in the impedance of the load.