Voltage Regulators VOLTAGE REGULATORSSignalOutputCircuitThe signal output circuit, which controls field excitation of the AC generator, increases ordecreases field excitation to either raise or lower the AC output voltage.FeedbackCircuitThe feedback circuit takes some of the output of the signal output circuit and feeds it back to theamplification circuit. It does this to prevent overshooting or undershooting of the desired voltageby slowing down the circuit response.ChangingOutputVoltageLet us consider an increase in generator load and, thereby, a drop in output voltage. First, thesensing circuit senses the decrease in output voltage as compared to the reference and lowers itsinput to the comparison circuit. Since the reference circuit is always a constant, the comparisoncircuit will develop an error signal due to the difference between the sensed voltage and thereference voltage. The error signal developed will be of a positive value with the magnitude ofthe signal dependent on the difference between the sensed voltage and the reference voltage.This output from the comparison circuit will then be amplified by the amplifier circuit and sentto the signal output circuit. The signal output circuit then increases field excitation to the ACgenerator. This increase in field excitation causes generated voltage to increase to the desiredoutput.If the load on the generator were decreased, the voltage output of the machine would rise. Theactions of the voltage regulator would then be the opposite of that for a lowering output voltage.In this case, the comparison circuit will develop a negative error signal whose magnitude is againdependent on the difference between the sensed voltage and the reference voltage. As a result,the signal output circuit will decrease field excitation to the AC generator, causing the generatedvoltage to decrease to the desired output.Rev. 0 Page 3 ES-11
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