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Heavy duty plugs and sockets
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Japan has a 100V network. Standard, domestic plugs and sockets are essentially identical to North American NEMA 1-15 and 5-15. Most plugs and sockets for higher currents and voltages are similar to North American NEMA configurations, but some are different (notably locking types). Examples of heavy duty single phase, split-phase or three-phase devices are shown below.

Note that the domestic voltage in Japan in 100V, but there are two network systems that differ with respect to frequency. The first generator was installed in 1895 in Tokyo by the German company AEG (50Hz). A year later the U.S. company General Electric installed a 60Hz generator in Osaka. Still today, the northeastern part of the country has 50Hz, while the southwestern part has 60Hz.

 

JP_200V socket JP_250V 15A 3-phase socket Japanese 4 pin 15A 250V plug
Japanese 4 pin 20A 250V plug

Japanese 15A 250V plug
Meikosha 15A 250V socket
Japanese 20A-250V 2-pin socket Japanese 20A-250V 2-pin plug

1 Japanese 200V, 15-20A single phase socket. The right hand, U-shaped slot is the earth connection. In addition there is also a connector - hidden behind the flap below the outlet - for a ground adapter (see type A/B domestic plugs, item 6). 200V originates from a 208V nominal voltage system, which means 208V at the point of supply and an utilization voltage of 200V 'at home'. Usually there is a 3-5% voltage drop in transport lines from transformer station to residence. See  scheme of Y-transformer below. Brand name: National (Panasonic). Image no. 5 shows a matching 15A plug.    {WaO}
2, 3 3-phase, earthed socket and plug, rated at 15A-250V. To wire up the plug you simply have to lift up the brown, circular base plate. The scheme of a 3-phase, Y-connected transformer (at the bottom of the page) shows the wiring of this type of plugs. Brand name of both socket and plug: Meikōsha, Tokyo, Japan.   {WaO}
4 Plug similar to no. 3, but rated at 20A-250V. Plugs no. 3 and 4 are depicted in the same scale. Models are idential to respectively NEMA 18-15P and 18-20P. Brand name: Meikōsha.   {FSE}
5, 6
Socket and plug rated at 15A-250V. The schemes show the difference between a 15A and 20A 250V plug.
Brand name: Meikōsha.
   {FSE}
7, 8
Not earthed, 2-pin 20A-250V socket and plug. Models are identical to NEMA 2-20R/P (see North American heavy duty page). Brand name: National (Panasonic) / Meikōsha.   {DH} {FSE}

Japanese 15A-250V 3-pin split-phase plug Japanese 20A-250V 3-pin split-phase plug
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JP_250V 20A twist socket
JP_250V 20A 15A twist plug JP_250V 20A 3-phase connector JP_250V 20A 3-phase plug

9 Plug rated at 15A-250V. Pin size and orientation is identical to the standard 10A Australasian plug. None of the pins has an indication with respect to wiring. It seems likely that it is a split-phase plug, comparable to the 20A version (see no. 10).
A comparable NEMA configuration does not exist, but the Japanese plug is identical to an outdated U.S. 15A-125V / 10A-250V single phase model (see page on North American classic plugs and sockets). Brand name: Meikōsha.
   {FSE}
10 Unearthed 20A-250V split-phase plug. W-pole + one of the angled poles = 120V. Both angled poles = 208V, see scheme below. Model identical to NEMA 10-20P (see North American dual voltage page). Brand name: Meikōsha.   {FSE}
11, 12
Locking type 20A-250V single phase socket and plug. To wire up the plug you have to lift up the white base plate.
A different shape of the earth pin makes the Japanese model incompatible with NEMA L6-20. Brand name: Meikōsha.   {WaO}
13, 14 Locking type 20A-250V four wire (3-phase + earth) outlet and plug. The model differs from any of the NEMA 3P, 4W configurations. Brand name: Meikōsha.   {FS}

 


Split-phase scheme


3-phase wye-connected transformer


Split-phase wiring offers both single phase 125V and 250V. To achieve this the output coil of the transformer is center-tapped (red dot in the scheme) and connected to neutral.
 
X-W (neutral) as well as Y-W = 125V. Because of alternating current the two live poles are out of phase, therefore X-Y = 250V

The secondary coil of a 3-phase Y-connected transformer has four conductors. In the example shown there is 208 Volt between two phases (1-2, or 1-3, or 2-3). Between the neutral connector and one of the phases there is 120 Volt (= 208 / √3).

Note that in both schemes given voltages are nominal voltages that are dependent of the voltage at the input side of the transformer.

 


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