LineInteractive

Line-interactive is a category of uninterruptible power supply (UPS) technology that combines automatic voltage regulation with a battery-backed inverter. It is designed to protect electronic equipment from common power disturbances by maintaining a stable output voltage while providing battery backup during longer outages.

In normal operation, the mains supply feeds the load directly, while a buck-boost transformer and control circuitry detect voltage deviations and adjust the taps to keep the output near the nominal level. This regulation helps correct small sags and surges without drawing on the battery. When the input voltage falls outside the acceptable window or a power outage occurs, an automatic transfer switch routes the load through the inverter and battery to continue supplying power. Transfer times are typically brief, on the order of milliseconds.

Typical components include an autotransformer-based buck-boost regulator, an inverter stage, a battery bank (often sealed lead-acid), a battery charger, and control electronics. Line-interactive UPS devices commonly range from a few hundred to several thousand VA and are popular for home and small business use, especially in regions with moderate voltage fluctuations.

Advantages and limitations:

- Provides voltage regulation without battery use for minor fluctuations, improving efficiency and reducing battery wear compared with online designs.

- More affordable and compact than online double-conversion UPS systems.

- Not ideal for constant, high-demand, or critical-load scenarios requiring uninterrupted, perfectly clean power; longer outages will deplete the battery, and isolation from input distortion is not as complete as online units.

See also: uninterruptible power supply, automatic voltage regulator, buck-boost transformer.