Automatic Voltage Regulators
Basically the AVR or Automatic Voltage Regulators function for generator is to ensure voltage generated from power generator running smooth to maintain the stable voltage in specified limit. It can stabilize the voltage value when suddenly change of load for power supply demand.
If the generator running in parallel condition,the AVR can controlled the voltage that it produce to ensure of equal value for reactive load sharing. For the big system of interconnected power distribution with parallel design,it must have a full controlled and transient stability particular must added for requirement to the Automatic Voltage regulator for generator.
The AVR can operated in two condition controlled.It is from manual control or automatic control with standard limited parameter that required for generator. This controlled must be provided if it not available for the generator system to ensure it smooth running without any problem
Basic principles for AVR
A signal proportional to generator terminal voltage obtained from the rectified output of a voltage transformer is compared to a stabilized reference voltage obtained within the regulator.
If it detected any abnormal,different or error signal, it will amplified and control the excitation supply, increase or decrease the input to the main field winding or exciter field.The main purpose is to reduce the error signal to zero or an acceptable value.
Adjustment of the set voltage is obtained either by adjustment of the reference voltage or by adjusting the proportion of machine voltage compared to the reference voltage. The stabilizing loop is included to prevent hunting.Below is basic diagram for AVR circuit.