IEC 60309
IEC 60309 (formerly IEC 309 and CEE 17, also published by CENELEC as EN 60309) is an international standard from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purposes". The highest voltage allowed by the standard is 690 V DC or AC; the highest current, 125 A; and the highest frequency, 500 Hz. The temperature range is −25 °C to 40 °C.
There is a range of plugs and sockets of different sizes with differing numbers of pins, depending on the current supplied and number of phases accommodated. The fittings are popular in open-air conditions, as they include IP44 weather-proofing. They are also sometimes used in situations where their special capabilities (such as high current rating or three-phase facilities) are not needed, to discourage potential users from connecting domestic appliances to the sockets, as 'normal' domestic plug-tops will not fit.
The cable connectors and sockets are keyed and colour-coded, according to the voltage range and frequency used; common colours for 50–60 Hz AC power are yellow for 100–130 volts, blue for 200–250 volts, and red for 400–480 volts. The blue fittings are often used for providing weather-proofed exterior sockets for outdoor apparatus. In camping situations, the large 32 A blue fittings provide power to static caravans, whilst the smaller blue 16 A version powers touring caravans and tents. The yellow fittings are used to provide transformer isolated 110 V supplies for UK construction sites to reduce the risk of electric shock, and this use spills over into uses of power tools outside of the construction site environment. The red three-phase versions are used for three-phase portable equipment.
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