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 · MBP
UPS maintenance bypass
An arrangement of interlocked switches that routes the load around a UPS so the UPS can be isolated for work.
In plain English
What does UPS maintenance bypass mean?
A UPS maintenance bypass is a set of switches, usually input, output and bypass, that lets the load be connected directly to the bypass supply while the UPS is fully isolated. It is normally external to the UPS cabinet so that the UPS itself can be removed without disturbing the load wiring.
A simple example
Single-line diagrams show the UPS between an input switch and an output switch, with a bypass switch connecting the input supply directly to the output busbar. Key interlocks or a make-before-break sequence prevent the UPS inverter from being paralleled with an unsynchronised bypass.
What the drawings help you do
The symbol does not tell you the sequence of operation or whether the UPS static bypass must be engaged first. Those steps are critical and must be written on the operating label or switching instruction.
This particular reference
An arrangement of interlocked switches that routes the load around a UPS so the UPS can be isolated for work. A maintenance bypass is external switching around the whole UPS; the static bypass is an internal electronic path.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: DC UPS, AC UPS and capacitor buffer modules · IEC graphical symbols for diagrams
SLD · MBP
What it represents
A UPS maintenance bypass is a set of switches, usually input, output and bypass, that lets the load be connected directly to the bypass supply while the UPS is fully isolated. It is normally external to the UPS cabinet so that the UPS itself can be removed without disturbing the load wiring.
Single-line diagrams show the UPS between an input switch and an output switch, with a bypass switch connecting the input supply directly to the output busbar. Key interlocks or a make-before-break sequence prevent the UPS inverter from being paralleled with an unsynchronised bypass.
The symbol does not tell you the sequence of operation or whether the UPS static bypass must be engaged first. Those steps are critical and must be written on the operating label or switching instruction.
How to read it
- Identify the three switches and their interlock.
- The bypass source may differ from the UPS rectifier source.
Information to show or reference
- State ratings of each switch.
- Show interlocks.
- Reference operating sequence.
A distinction that matters
A maintenance bypass is external switching around the whole UPS; the static bypass is an internal electronic path.
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 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.
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