Brushless exciter protection circuit

摘要

A protection circuit for a brushless excitation system is provided which directly monitors the output voltage of the diode bridge rectifier of the system. The protection circuit includes a reference signal generator subcircuit which provides a reference signal which tracks the dc output voltage of the diode bridge. The reference signal can vary as the system voltage is varied under certain circumstances. The protection circuit also provides for the calculation of a predetermined percentage of the reference signal voltage to create a tolerance band for testing the actual output voltage of the diode bridge rectifier. The percentage represents an acceptable limit of the ratio of a peak-to-peak ripple of the reference signal to the dc voltage of the reference signal. Using the reference signal and the percentage value to create a tolerance band, a comparator is used to test the actual output voltage of the diode bridge to determine if the output voltage is within the tolerance band. If the output voltage is detected to be outside the tolerance band, then the comparator generates a signal which activates trip circuitry associated with the system to interrupt the system. A subcircuit is also provided to inhibit a trip if the signal being tested is not within a minimum protection range.