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Questions about three-phase 400V industrial plugs for welders, machines and power tools.
Red industrial plugs are the usual colour for three-phase supplies in the 380 to 480V band, which includes 400V. They belong to the international IEC 60309 family of industrial plugs and sockets (sometimes called CEE or commando type), and are used for three-phase welders, compressors, machine tools and similar equipment.The colour shows the voltage group only. The pin layout, current rating and keying also have to match the socket, so the plug has to suit both the equipment and the supply it is plugged into.
A 4 pin plug carries three phases plus earth (written 3P+E) and has no neutral. A 5 pin plug carries three phases, neutral and earth (3P+N+E). The two are not interchangeable, and a 4 pin plug will not mate with a 5 pin socket of the same rating.Many three-phase motors and welders need no neutral and use the 4 pin type, but equipment that has single-phase circuits inside, such as controls or auxiliaries, may need the neutral. Choosing 4 pin where neutral is needed is a common specification error.
The IP code describes protection against solids and water. IP44 is a splash-proof rating and is commonly the minimum for this type of plug, suitable for workshops and sheltered outdoor areas. IP67 means dust-tight and protected against temporary immersion, and is used for wet, harsh or washdown conditions.The rating only applies when the cable entry is correctly sealed and the plug is properly engaged in a matching socket. A good plug body with a poorly fitted cable gland can still let water in.
No. Colour, pin count, current rating and the position of the earth contact (the clock position, such as 6h) must all agree. Each voltage and configuration has its own earth position, and moulded keyways stop a plug going into a socket that does not match.Two parts that look alike can still be incompatible if the keyway or earth position differs. Never force a plug into a socket or modify either to make it fit. Check the markings and the data sheet, and use a plug that matches the socket.