SOI
Socket outlet with interlocked switch
Plan mark for an outlet whose switch is mechanically interlocked so a plug cannot be inserted or withdrawn while live.
IEC
IEC · SO3
Three-phase socket outlet
Installation plan mark for a polyphase socket outlet, shown with three conductor strokes on the outlet lead.
In plain English
What does Three-phase socket outlet mean?
A three-phase socket outlet supplies portable or semi-fixed three-phase equipment such as compressors, welders, kilns and site distribution boards. Plan symbols typically show the outlet form with three short oblique strokes, the same convention used on single-line diagrams to indicate three conductors.
A simple example
Because three-phase outlets differ in pin arrangement (with or without neutral), current rating and phase rotation, the symbol is nearly always accompanied by text such as 20 A 5P or 32 A 4P. The electrician needs this to choose the accessory and to confirm phase rotation at commissioning.
What the drawings help you do
The strokes indicate phase conductors only. They do not show whether neutral and protective earth are included, and they do not replace the circuit schedule entry for cable size and protective device.
This particular reference
Installation plan mark for a polyphase socket outlet, shown with three conductor strokes on the outlet lead. A single-phase earthed outlet has no conductor strokes; the three strokes mark the polyphase supply.
- Phase
- One of the related AC waveforms in a power system.
- 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: IEC graphical symbols for diagrams · Autodesk IEC-60617 preview: Single and duplex power-receptacle forms · Electrical installation design methodology and references
IEC · Three-phase socket outlet
IEC 60617 installation-plan style (architectural and topographical installation symbols); independently drawn, not certified IEC geometry or a database identifier.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
GA · SO3
What it represents
A three-phase socket outlet supplies portable or semi-fixed three-phase equipment such as compressors, welders, kilns and site distribution boards. Plan symbols typically show the outlet form with three short oblique strokes, the same convention used on single-line diagrams to indicate three conductors.
Because three-phase outlets differ in pin arrangement (with or without neutral), current rating and phase rotation, the symbol is nearly always accompanied by text such as 20 A 5P or 32 A 4P. The electrician needs this to choose the accessory and to confirm phase rotation at commissioning.
The strokes indicate phase conductors only. They do not show whether neutral and protective earth are included, and they do not replace the circuit schedule entry for cable size and protective device.
How to read it
- Count the strokes and read the pole annotation; a 4-pin and a 5-pin outlet look the same without the label.
- Check whether an isolator or interlocked switch is shown in the same position.
Information to show or reference
- Write current rating and pin count beside the symbol.
- State whether a neutral is required.
- Record phase rotation verification in the commissioning checklist.
A distinction that matters
A single-phase earthed outlet has no conductor strokes; the three strokes mark the polyphase supply.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC committee context for graphical symbols used in diagrams and installation documents; not a source of reproduced artwork.
Autodesk IEC-60617 preview: Single and duplex power-receptacle forms
Public receptacle family in an IEC-oriented CAD library, useful for comparing schematic receptacle forms with plan marks.
Electrical installation design methodology and references
Installation design methodology context: circuits, outlets and final distribution are planned before symbols are placed.
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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