UPS AC
AC uninterruptible power supply
An AC UPS provides a documented AC load supply through its normal and backup operating arrangements.
SLD / Schematic
Symbols · 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.
In plain English
What does Online double-conversion UPS mean?
In an online double-conversion UPS the load is always supplied by the inverter. The rectifier converts incoming AC to DC, the battery floats on the DC link, and the inverter produces a regulated output that is independent of input voltage and frequency variations. When the input fails, the battery simply takes over the DC link with no transfer.
A simple example
Single-line diagrams show rectifier and inverter blocks in series with the battery connected between them, a static bypass switch in parallel, and often a separate bypass input and an external maintenance bypass. Output isolation transformers may also be shown.
What the drawings help you do
The double-conversion path costs a few per cent in efficiency and some units offer an eco mode that runs on bypass, which changes the protection the load actually receives. The symbol does not show which mode is set, battery autonomy or the bypass source arrangement.
This particular reference
A UPS whose rectifier and inverter carry the load continuously, with the battery on the DC link and a static bypass. An online UPS powers the load through the inverter all the time; a line-interactive UPS passes mains to the load and only inverts during disturbances.
- DC
- Direct current: electricity flowing in one direction.
- AC
- Alternating current: electricity whose direction changes periodically.
- Winding
- A coil of conductor inside an electrical machine or transformer.
Read the source: DC UPS, AC UPS and capacitor buffer modules · Multilevel NPC converter application context
SLD · UPS VFI
What it represents
In an online double-conversion UPS the load is always supplied by the inverter. The rectifier converts incoming AC to DC, the battery floats on the DC link, and the inverter produces a regulated output that is independent of input voltage and frequency variations. When the input fails, the battery simply takes over the DC link with no transfer.
Single-line diagrams show rectifier and inverter blocks in series with the battery connected between them, a static bypass switch in parallel, and often a separate bypass input and an external maintenance bypass. Output isolation transformers may also be shown.
The double-conversion path costs a few per cent in efficiency and some units offer an eco mode that runs on bypass, which changes the protection the load actually receives. The symbol does not show which mode is set, battery autonomy or the bypass source arrangement.
How to read it
- Look for separate rectifier and bypass inputs; they may come from different boards.
- Check whether eco mode is enabled.
Information to show or reference
- State kVA, kW and battery autonomy.
- Show static bypass and maintenance bypass.
- Reference operating mode.
A distinction that matters
An online UPS powers the load through the inverter all the time; a line-interactive UPS passes mains to the load and only inverts during disturbances.
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.
Multilevel NPC converter application context
Public UPS converter design context.
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.
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