AS 3112 is an Australian standard for mains power plug. It is also known as a Type I plug.
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The plug matching the pictured socket, used in Australia, Argentina, New Zealand, Fiji, Papua New Guinea and Tokelau, has an earthing pin and two flat pins forming an inverted V-shape. There is an unearthed version of this plug as well, with only two flat V-aligned pins. These flat blades measure 6.5 by 1.6 mm and are set 30° to the vertical on a nominal pitch of 13.7 mm. A standard power point in Australia provides a nominal voltage of 230 volts at a maximum of 10 amps, as in the UK, its outlets are individually switched for extra safety.[1].
There are several AS/NZS 3112 plug variants,[2] including one with a wider ground pin used for devices drawing up to 15 amperes; sockets supporting this pin will also accept 10 A plugs. There is also a 20 A variant, with all three pins oversized, and 25 and 32 A variants, with the 20 A larger pins and the earthing pin forming an inverted "L" for the 25 A and a horizontal "U" for the 32 A. These sockets accept plugs of equal or of a lower current capacity, but not of higher capacity. For example, a 10 A plug will fit all sockets but a 20 A plug will fit only 20, 25 and 32 A outlets.
A variant of the Australasian standard 10 amperes plug has a socket on the back to allow connection of a second appliance to the same outlet. This type of plug is known officially as a "socket adapter plug" but is referred to colloquially as a "piggy-back plug". The plug itself is no longer available for separate retail sale, but only as part of a pre-assembled extension cord, or by special order. This ban was introduced because someone constructed an extension cord with a piggy-back plug on one end and a normal plug on the other, to connect the wiring in a garden shed to a socket in the adjacent house.The obvious hazard was that the pins of the plug on the other end would be live if the cord was attached to the supply end first. The person concerned did just that and received a fatal electric shock when contacting the live pins on the other end.
Other versions include a round earth plug with a rating of 10 A, and a 110 V 10 A version that has round active & neutral pins with a flat earth pin. Care should be taken if Argentinian standards or faulty wiring swaps the active and neutral pins. Care should be taken with the 10 A version with the round pin as physically compatible, but electrically incompatible NEMA 7–15 connector used for 277 V 15 A connections is encountered in commercial or industrial settings in the Americas.
A commonly used version has only two pins, without the Earthing pin. These are for devices where it is assumed that other safety standards are in use (e.g. earth-leakage, double insulation, etc.).
The Chinese CPCS-CCC (Chinese 10 A/250 V) plugs and sockets are almost identical, differing by only 1mm longer pins and installed "upside down". Note that whilst AS 3112 plugs will physically connect, they may not be electrically compatible to the Chinese 220 V standards.
Australia used to have the earth pin facing upwards like China still does, but changed the practice in the 1950s, so that the earth will be the last to lose contact if the inserted plug is tugged downwards. If products destined for the Chinese market are exported, the bottom entry plug becomes a top entry plug, and the customer will often take advantage of the situation by suspending the power cord upwards.
Australia's standard plug/socket system was originally codified as standard C112 (floated provisionally in 1937, and adopted as a formal standard in 1938), which was superseded by AS 3112 in 1990. An American version was manufactured and used for grounded equipment (like washers in laundry rooms) in the 1940s and early 1950s, and appears to have existed as far back as 1916, shown in US patent 1,179,728 [3]. Australian plugs will fit these American outlets perfectly. There's also another American outlet, the NEMA 10-20R, that looks quite similar, but is about 10% larger[4]. A major update AS/NZS 3112:2000 was released in 2000 and mandated insulated pins by 2005. The current issue of the standard is AS/NZS 3112:2004 which introduced more stringent testing procedures to test for bending of the pins and subtle changes to the radius of the pin tips.
In Brazil, this kind of plug is commonly found in high-power appliances like air conditioners, dishwashers, and household ovens. The reasons why they have been (unofficially) adopted for this use may be the robustness and high-current bearing capabilities, the impossibility of inverting phase and neutral pins, or the fact that Argentina, a border country, uses this plug and used to be more developed than Brazil in the past (meaning that people had more access to some kinds of electrical appliances and/or to electricity itself) so there may have been a flux of high-powered appliances from Argentina to Brazil in some point of time.
Nowadays, Brazil has adopted the IEC 60906-1 standard, which prescribes a high-current version, with earth pin and slightly larger pins (4.8mm instead of 4mm) that can carry up to 20A. New apparatus has been sold with the new plug, so the tendency is the usage of the "Australian" plug to fade away.