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ITFrequently Asked Questions · AVR
What types of AVR are there?
There are three main types: relay (electromechanical, affordable and fast, adjusting in steps), servo motor (smoother and more precise regulation, slower response) and static (fully electronic with thyristors, very fast and with no moving parts).
AVRs (voltage stabilisers) differ mainly in how they correct the voltage. Relay-type units switch the taps of a transformer with electromechanical relays: they are economical, compact and fast, but correct the voltage in steps, so the output varies within a band. Servo stabilisers use a motor that moves a brush over a variable transformer: they give smooth, accurate regulation and handle large loads, but respond more slowly and have moving parts that need maintenance.
There are also static, fully electronic stabilisers, which use thyristors or other semiconductor devices instead of relays or a motor. They have no moving parts, respond very quickly and run silently, which is why they are preferred for sensitive loads.
Practical tip: for household appliances and office equipment, a relay-type AVR is usually enough. For machinery, air conditioning or a whole installation, choose a servo or static type. A common mistake is choosing on power rating alone without checking the input voltage range the AVR can correct, which must cover the actual fluctuations of the grid in your area.