Japan's electrical supply

[edexlab]

I was talking today to a colleague who went to Japan to do an install and he mentioned something which he said he'd never got round to researching. ...

He said the supply there was 200 volts
3 phase ,100v 1 phase, 50 or 60 Hz depending on region in the country

Yet when he tested the supply between lines and earth he got 100v to earth on 2 phases and nothing between 3rd phase and earth,
(between phases it was 200v)

This made him suspect something was wrong so he consulted a native electrician who said this was correct?

Does anybody know how this system works????
It's just for my own curiosity really I've looked online but have yet to find anything which explains it well

 

[edexlab]

Just found a bit more info

They use a "3 phase open delta system four wire earthed mid point of one phase"

 

[Sintra]

They use a 3 phase open delta system which got me confused the first time I was there. The attached picture should help explain.

Edit just notice you'd found out about the open delta.

 

[edexlab]

Yup but thanks anyway !
its all making more sense now

 

[marconi]

They use a 3 phase open delta system which got me confused the first time I was there. The attached picture should help explain.

Edit just notice you'd found out about the open delta.

Would you know why the Japanese settled on this system?

 

[UKMeterman]

In the recovery after the war you had American and also European support, that is why you get some parts working to base American specs 110V 60Hz and so on and also 50Hz in other parts.

 

[edexlab]

This is a brief explanation I found explaining the advantages/disadvantages also as the US had a large influence in rebuilding the country it's a system similar to their own split phase supply.

"Where the three-phase load is small relative to the total load, two individual transformers may be used instead of the three for a "full delta" or a three-phase transformer, thus providing a variety of voltages at reduced cost.
This is called "open-delta high-leg", and has a reduced capacity relative to a full delta."


Disadvantages;
" Phase balancing is not great, but it is not worse than split-phase system.

One of the phase-to-neutral voltage (phase 'B') is different from the other two. This can be fixed with an autotransformer, but that is an added expense.

Commonly there is a high-leg to neutral load limit.
One transformer manufacturer's page suggests that High-leg to neutral loading to not exceed 5% of transformer capacity."

 

[marconi]

Dear edexlab, Sintra and UK Meterman - Thank you for taking the time to answer my query. I have learned something from your experience.

 

[marconi]

Dear edexlab and Sintra, A supplementary question if I may - how are homes normally supplied? Do they have a 4 wire supply or something else?

 

[shanky887614]

Dear edexlab and Sintra, A supplementary question if I may - how are homes normally supplied? Do they have a 4 wire supply or something else?

i cant speak for japan but in the us im guessing 4wire L1,L2,N and E

they run on 110spn 220polyphase

 

[Sintra]

Dear edexlab and Sintra, A supplementary question if I may - how are homes normally supplied? Do they have a 4 wire supply or something else?

i cant speak for japan but in the us im guessing 4wire L1,L2,N and E

they run on 110spn 220polyphase

I would imagine it is the way shanky has said with the voltages being 100V & 200V respectively.

 

[UKMeterman]

I would imagine it is the way shanky has said with the voltages being 100V & 200V respectively.

The case we are discussing could be corner grounded delta.

 

[shanky887614]

The case we are discussing could be corner grounded delta.

Marconi asked how they are normally and that is a good question.

it depends on the prefectur
acording to wiki there is 47

 

[norcal]

In the recovery after the war you had American and also European support, that is why you get some parts working to base American specs 110V 60Hz and so on and also 50Hz in other parts.

The US has not used 110, 220 volts since before WWII, it was raised to 115/230V before going to the current 120/240V standard, but then there is 208Y/120V, and 480Y/277V, 400/230V is way simpler but that is what happens because Edison's 110V DC was well established before AEG started peddling their 220V 50 HZ system, Westinghouse had make their AC distribution compatible with Edison's 110V lighting, BTW Tesla was in favor of 60 HZ, 25 & 50HZ was used in the past in the US before settling on 60 HZ.

 

[norcal]

i cant speak for japan but in the us im guessing 4wire L1,L2,N and E

they run on 110spn 220polyphase

Not true, 110/ 220 is obsolete in the US, there 120/240V, single phase, 120/240V 3 phase (some power companies are not supplying it to new customers anymore) I do not care for it because of the 208V high leg, 208Y/120V, and 480Y/277V, Canada uses 600Y/347V rather then 480Y/277V. The primary users of "110, 220" are DIY'ers, but then there are the idiots who write "110/208V'' on a panel circuit directory.