Answer / kj

An AVR (automatic voltage regulator) works by supplying a
variable voltage to the field of an alternator to control
the output voltage.
The AVR senses the output voltage and compares it to a
setpoint which is usually set by a pot on the board.
It uses either the output voltage from the alterantor or
another source (e.g. PMG permenant magnet generator) to
supply the voltage to the field. The voltage to the field
is DC so the supply to the AVR is rectified before it is
used for the filed.

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