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.
SLD
Symbols · UPS VFD
Offline standby UPS
A UPS that passes raw mains straight to the load and starts its inverter only when mains is lost.
In plain English
What does Offline standby UPS mean?
An offline or standby UPS connects the load directly to mains through a transfer relay. A separate charger keeps the battery topped up, and the inverter starts only when mains fails, at which point the relay transfers the load. Transfer typically takes several milliseconds to around ten milliseconds.
A simple example
Drawings show the mains path through a changeover contact to the output, with the charger, battery and inverter forming a parallel branch that connects to the other contact position. These units are mainly small desktop or control panel units.
What the drawings help you do
The load sees mains disturbances and the transfer gap, and the inverter waveform may be stepped rather than sinusoidal. The symbol does not show waveform quality, transfer time or whether surge filtering is included.
This particular reference
A UPS that passes raw mains straight to the load and starts its inverter only when mains is lost. An offline UPS gives no correction until it transfers; an online UPS conditions the output continuously.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
Read the source: DC UPS, AC UPS and capacitor buffer modules · DIN-rail power supply, buffer, redundancy and UPS families
SLD / Schematic · UPS VFD
What it represents
An offline or standby UPS connects the load directly to mains through a transfer relay. A separate charger keeps the battery topped up, and the inverter starts only when mains fails, at which point the relay transfers the load. Transfer typically takes several milliseconds to around ten milliseconds.
Drawings show the mains path through a changeover contact to the output, with the charger, battery and inverter forming a parallel branch that connects to the other contact position. These units are mainly small desktop or control panel units.
The load sees mains disturbances and the transfer gap, and the inverter waveform may be stepped rather than sinusoidal. The symbol does not show waveform quality, transfer time or whether surge filtering is included.
How to read it
- The normal path has no conversion stage.
- Check output waveform type for sensitive loads.
Information to show or reference
- State VA rating and transfer time.
- Show transfer relay, charger and inverter.
- Reference output waveform.
A distinction that matters
An offline UPS gives no correction until it transfers; an online UPS conditions the output continuously.
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.
DIN-rail power supply, buffer, redundancy and UPS families
Public DIN-rail UPS family 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.
Explore related references
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A UPS whose rectifier and inverter carry the load continuously, with the battery on the DC link and a static bypass.
SLD
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AC uninterruptible power supply
An AC UPS provides a documented AC load supply through its normal and backup operating arrangements.
SLD / Schematic
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