# Line-interactive UPS

Canonical URL: https://eloragrid.ai/symbols/line-interactive-ups
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: UPS VI
Drawing use: SLD
Reference families: IEC, IEEE / ANSI

A UPS that passes mains to the load through a voltage-correcting stage and switches to its bidirectional inverter on failure.

## In plain English

### What does Line-interactive UPS mean?

A line-interactive UPS supplies the load from mains in normal operation, using an automatic voltage regulation stage, often a tapped autotransformer, to correct sags and swells. One bidirectional converter charges the battery while mains is present and inverts from the battery when mains fails, with a short transfer of a few milliseconds.

### A simple example

Drawings show the mains path through a voltage regulating element and a transfer switch to the output, with the bidirectional converter and battery connected alongside the output. It is common for small to medium ratings serving IT equipment and controls.

### What the drawings help you do

Output frequency follows the mains in normal operation, so the load is not protected from frequency variations, which matters on generator supplies. The symbol does not show the transfer time or the voltage correction range.

### This particular reference

A UPS that passes mains to the load through a voltage-correcting stage and switches to its bidirectional inverter on failure. A line-interactive UPS corrects voltage on the mains path; an offline UPS passes mains without correction until it transfers.

### Terms

- Winding: A coil of conductor inside an electrical machine or transformer.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [DC UPS, AC UPS and capacitor buffer modules](https://www.phoenixcontact.com/en-gb/products/uninterruptible-power-supplies-ups)
- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

A line-interactive UPS supplies the load from mains in normal operation, using an automatic voltage regulation stage, often a tapped autotransformer, to correct sags and swells. One bidirectional converter charges the battery while mains is present and inverts from the battery when mains fails, with a short transfer of a few milliseconds.
Drawings show the mains path through a voltage regulating element and a transfer switch to the output, with the bidirectional converter and battery connected alongside the output. It is common for small to medium ratings serving IT equipment and controls.
Output frequency follows the mains in normal operation, so the load is not protected from frequency variations, which matters on generator supplies. The symbol does not show the transfer time or the voltage correction range.

## How to read it

- Look for a tapped transformer or regulation element in the mains path.
- Expect a short transfer on mains failure.

## Information to show or reference

- State VA rating, transfer time and correction range.
- Show battery and converter connection.
- Reference generator compatibility.

## Important distinction

A line-interactive UPS corrects voltage on the mains path; an offline UPS passes mains without correction until it transfers.

## Facts

- Normal load path: Mains with voltage regulation
- Converter: One bidirectional stage
- Transfer: A few milliseconds
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [DC UPS, AC UPS and capacitor buffer modules](https://www.phoenixcontact.com/en-gb/products/uninterruptible-power-supplies-ups) — Phoenix Contact. Public UPS function context.
- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC graphical symbol context for converters and switches.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.