An automatic voltage regulator (AVR) is a device that is required when the utility voltage exceeds acceptable tolerances of +/- 10%.
Eg. Where the utility voltage is 220 volts, the acceptable tolerance is between 190V and 242V. An automatic voltage regulator will accept input tolerances of up to 30% above and below the utility voltage and provide an output regulation of +/-5%. Automatic Voltage Regulators are available as either 3 phase or single phase devices. An automatic voltage regulator cannot take the place of UPS’s as they provide no backup in the event of a utility power outage.