What Does an AVR Do (and Why It Is Not a UPS)

Q: What does an Automatic Voltage Regulator do for me?

A: An Automatic Voltage Regulation device (AVR or AVS — automatic voltage stabiliser) keeps the grid supply voltage feeding the load within ±10% of the 220 VAC nominal, even if the upstream grid varies by as much as +20% / –40% of nominal. Most decent AVRs also include filtering circuits to attenuate noise on the grid supply side.

Important caveat: an AVR or AVS is not a UPS. It has no inverter and no battery. When mains fails, an AVR drops the load. Use an AVR for sites where voltage instability is the problem but outages are rare; use a UPS (with built-in or upstream AVR) when outages also need to be covered.

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