UPS VFI
Online double-conversion UPS
A UPS whose rectifier and inverter carry the load continuously, with the battery on the DC link and a static bypass.
SLD
Symbols · UPS VI
Line-interactive UPS
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.
- 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.
Read the source: DC UPS, AC UPS and capacitor buffer modules · IEC graphical symbols for diagrams
SLD · UPS VI
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.
A distinction that matters
A line-interactive UPS corrects voltage on the mains path; an offline UPS passes mains without correction until it transfers.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
DC UPS, AC UPS and capacitor buffer modules
Public UPS function context.
IEC graphical symbols for diagrams
IEC graphical symbol context for converters and switches.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
Explore related references
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Single-phase autotransformer
A single-phase autotransformer uses a winding portion shared electrically by its input and output circuits.
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