Museum of Plugs and Sockets logo, small IEC 60309 industrial standard
Basic information
navigation icon

navigation icon navigation icon


In the 1960s the IECEE (International Commission on the Rules for the Approval of Electrical Equipment) has defined the CEE 17 standard for plugs and sockets for industrial purpose. CEE is an abbreviation of Certification of Electrical Equipment.
CEE17 has been superseded by IEC 309 in 1983, and later renamed IEC 60309 standard (IEC = International Electrotechnical Commission).

In the UK the IEC 309 standard was adaopted as BS 4343 in 1968, and replaced by BS EN 60309 in 1999.

There are many types of IEC 60309 sockets, ouitlets, plugs, connectors and application inlets. They differ with respect to:
voltage:    <50 to 690 Volt AC and 50 to 250 Volt DC;
current:    16 to 125 Amp;
frequency: 50 or 60 Hz (for aircrafts >60 Hz).

Connections are either splash-proof (IP44), or waterproof (IP67).

All plugs and sockets have a protective earth (E) connection.
Three-phase devices exist with and without neutral connection.


Basic features of IEC 60309 plugs and sockets 1
IEC 60309 16A 3-phase 4-wire plug IEC 60309 16A 3-phase 5-wire socket (6h)
IEC 60309 16A single phase 3-wire socket (6h)
IEC 60309 32A 3-phase 5-wire socket (9h)

Plugs have round pins, arranged in a circle. The diameter of the earth pin (E) is always 2 mm larger than the other pins.
Male plugs and appliance inlets have a circular shroud. Sockets and connector plugs have matching recess.

Plugs and male inlets have a key (see image top left). Sockets and connectors have a matching, invariably down facing keyway.
The position of the (large) earth pin can be in one of 12 positions, described as clock positions (1 -12 hour), see image below.
The earth pin 6h clock position corresponds to the fixed position of the socket keyway.

ELV plugs and sockets have a different key system.

For each type of plug only one matching socket exists.
This ensures that connection is only possible when voltage, current, frequency and number of pins/contacts match.

Various configurations arise from differences in:
1. number of pins: 3, 4 or 5 (special variants with <5 pins exist),
2. earth pin clock position and
3. diameter of pin shroud / socket recess.

The scheme below shows that pin number and earth pin clock position results in 36 different configurations. Differences in diameter adds many more.

Colour codes 2
100 - 130 Volt AC 3

120/240 V split phase 60Hz (N.Am. only)
200 - 250 V 
50 - >259 V DC
380 - 480 V 
277 V 60 Hz (N.Am. only)
490 - 690 V 
100 - 500 Hz (among others used in aircrafts) 4
Colour codes for Extra Low Voltage:  violet for 20 - 25 V,  white for 40 - 50 V  (not in museum collection)


  Footnotes:   1. refers to devices rated at >50V; the museum does not have extra-low voltage (ELV) models.
  2. colour code of sockets is often restricted to the cover.   3. unless stated otherwise AC refers to either 50 or 60Hz.
  4. green is sometimes combined with another colour that indicates the voltage range.


IEC 60309 coloue code and keyway map

IEC 60309 socket and locked plug
IP44 splash-proof socket outlets and connector plugs have a spring loaded hinged cap. When a plug is inserted, the cap hooks over a lug on the plug and retains it in place. See image left.

IP 67 waterproof outlets have a gasket and twist-lock ring which seals outlet and plug together.


Wikipedia     Farnell     Mennekes     Scame 


Navigation icon D i g i t a l   M u s e u m   o f Navigation icon P l u g s   a n d   S o c k e t s Navigation icon