Alternator Voltage Regulator (AVR) is to maintain the terminal voltage of the alternator constant from no load to full load in respect of power factor and frequency. As it is known its terminal voltage decreases depending on the machine's reactance type of load, power factor and speed. A suitable control excitation is required to keep the alternator terminal voltage constant. A set protection is also to be given for the safety of the system.
"NAREN" AVR senses the alternator terminal voltage, varies the power fed to the field of the alternator to keep the terminal voltage constant irrespective of load conditions. This is achieved by thyristor controlled rectifier where the triggering phase angle of thyristor is varied by fast acting highly sensitive solid state control circuit.
NAREN VOLTAGE REGULATOR : Comprises of the following circuits on single P.C.B
Voltage build up circuit, to build the voltage from residual 50-60% terminal voltage
Stable reference, to give the constant voltage irrespective of the load and frequency
The Voltage sensing circuit gives reduced voltage which is proportional to the alternator voltage.
Error amplifier, amplifies the difference between the voltage sensed and the reference voltage.
Frequency role off, to reduce the terminal voltage in the event of low speeds of the
primover.
Snubber circuit across the semi-conductor to protect against the voltage surges.
Series choke to protect against current surges.
Thyristor controlled power circuit, to feed the variable power to the field.
