Droop is another name for proportional band in analogue control circuits. Droop may be electrical, mechanical, (RPM, position), pneumatic, or possibly some other variable.
If you want voltage drop, use Z (impedance) times I (current).
Bill
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Most generators have an automatic voltage regulator which modulates the field current of the machine to maintain a setpoint by using a feedback from VTs connected to the main terminals, or maybe connected to the load busbar or after a step-up transformer. It is the AVR which determines the droop characteristic: the AVR setpoint can be a constant value regardless of the load applied, or it can be made load-dependant by providing the AVR with an input from a CT on the main terminals of the machine. This latter mode is a voltage droop characteristic.
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