Is there a particular reason Japan is 100 volts?

[schmitt trigger]

And I mean a technical reason.

To the best of my knowledge, it is unique to Japan.
One would think that, Japanese people being frugal, would have chosen a higher voltage to reduce copper utilization.

[Alex Eisenhut]

Worse, half the place is 50Hz, the rest 60Hz. Fun!

https://www.japan-guide.com/e/e2225.html

Not as exciting as what they do in Brazil!

[tooki]

My 6 cents:

1. Japanese sockets are 2-pin only, and if you need ground bonding, you have an exposed screw for that (and a spade connector on appliance cords).
2. So they can't conveniently plug in plugs with ground without screwing/unscrewing, and therefore they need a less lethal voltage in case shit hits the fan (they do have GFCI).
3. Also, lower voltage reduces Y cap leakage, which helps increasing user experience (less mild tingling shock, less headphone hums, etc.) when grounding is not conveniently feasible.

That’s nothing but idle speculation. I’m quite certain Japan’s choice of 100V (or rather, its two decisions of 100V, since part of the country is 50Hz and part is 60Hz) predates any of those concerns by a long time.

[amyk]

I read that early arc-lighting generators and incandescent lamps ran at 100V, so that might've been a reason; or they just liked the nice round number of 100.

You could equally ask why a voltage of 120V or 240V was chosen by everyone else...

[Alex Eisenhut]

Maybe it was to sync up to 33 1/3 RPM records after 3 minutes?

[Mr. Scram]

240V wasn't chosen by everyone else. It took some doing to homogenise voltages around that number into one.

[rstofer]

You could equally ask why a voltage of 120V or 240V was chosen by everyone else...

If you go back in history in the US, we had 110V, 115V, 117V and, finally, 120V.  All were standards at the time.
If you read old schematics or old ARRL Handbooks, you will see these various voltages.

The phase-to-phase connection of the common residential voltages were, consequentially, 220V, 230V, 234V and, finally 240V.

[kosine]

As mentioned above, early electric carbon filament lamps were designed to run at 100V (late 1800s). This made them bright enough to compete with gas lighting and 100V was also considered safe.

Edison's DC system generated 110V at the power plants to allow for transmission loses. Tesla used the same voltage at AC when he built the first Niagara plant. Japan may have had more efficient transmission lines and used 100V throughout.

The 60Hz frequency comes from Tesla's polyphase motors, and has remained standard since.

[GeorgeOfTheJungle]

Not as exciting as what they do in Brazil!

What do they do in Brazil?

[tooki]

240V wasn't chosen by everyone else. It took some doing to homogenise voltages around that number into one.

And it’s actually 230V that they settled on, since it’s within the tolerance for both 220V and 240V, which were variously used.

And of course, there were also some system voltages that simply died out over time. Isn’t there still some weird low-frequency AC in some parts of USA for industry or something?

[janoc]

And of course, there were also some system voltages that simply died out over time. Isn’t there still some weird low-frequency AC in some parts of USA for industry or something?

You mean like Switzerland's (and also Austria's and Germany's) 15 kV, 16.7 Hz railway overhead wire voltage?

[langwadt]

Not as exciting as what they do in Brazil!

What do they do in Brazil?

https://www.worldstandards.eu/electricity/plug-voltage-by-country/brazil/ ?

[IanMacdonald]

The EU 230v is a piece of pure bureaucracy. It's actually 247v here. Notionally 240 +-6%. Many parts of Scotland have slightly high voltage, probably to allow for transmission drops.

High-ish supply voltages used to be a cause of frequent equipment faults in the days of valve equipment, since there often wasn't much tolerance on electrolytic cap ratings, etc. 

Interesting case here:

[glarsson]

What I get out of the wall sockets certainly changed. Before the EU change the voltage was a bit above 220V, now it is a bit above 230V. Usually I see about 235V.

[Seekonk]

The first US standard was 166.6 Hz.

[GeorgeOfTheJungle]

Before the EU change the voltage was a bit above 220V, now it is a bit above 230V. Usually I see about 235V.

Don't tell that to the remainers, please

[rstofer]

And of course, there were also some system voltages that simply died out over time. Isn’t there still some weird low-frequency AC in some parts of USA for industry or something?

Niagara Falls used to generate 25 Hz and parts of New York City continued using it up until the early 2000s.  I'm pretty sure it is gone now since the hydro plant stopped making it in 2006

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4412948

60 Hz is our competitive advantage over the 50 Hz world.  It takes less iron to make motors and transformers thus saving costs.  Besides, we work just a little faster.

[tooki]

Why can’t we use higher frequency (for example, the 400Hz used on aircraft) for everything?

[glarsson]

Larger transmission losses. Aircrafts are smaller and has low weight as a priority. Electric trains are the opposite. Long lines and weight is an advantage and, in many countries, use 16 2/3 Hz.

[filssavi]

The only switch that would kind of make sense with the current state of power electronic would be to switch from AC to DC for distribution, not regular transmission, there AC is still going strong for now.

The great majority of loads right now (I don't have numbers but I bet is over 80% of the total residental and small industrial installed power) rectify the AC to DC anyway, and especially in residential use the conversion efficiencies are quite low.

switches will get bigger but they are being replaced by semiconductors anyway
Circuit creakers will get bigger, but it is not the end of the world

Unfortunately this will probably never happen since the costs would be way to high and so we will keep 240V/50Hz or 120V/60Hz forever I think

[GeorgeOfTheJungle]

60 Hz is our competitive advantage over the 50 Hz world.  It takes less iron to make motors and transformers thus saving costs.

I still remember that in the past, all the US wall chargers, those that had iron transformers inside, ran crazy hot in Europe, due to that.

There are more hysteresis and eddy-current losses, and the lower voltage means you need more copper in the wirings everywhere, and/or more I²R losses.

[mmagin]

The only switch that would kind of make sense with the current state of power electronic would be to switch from AC to DC for distribution, not regular transmission, there AC is still going strong for now.

The great majority of loads right now (I don't have numbers but I bet is over 80% of the total residental and small industrial installed power) rectify the AC to DC anyway, and especially in residential use the conversion efficiencies are quite low.

So, uh, like distributing 120-160 VDC (or equivalently 240-320 VDC)?  You'd need more expensive circuit breakers / fuses.  Also you'd have a harder time detecting ground faults (and such faults would lead to corrosion issues).  And it only saves on the initial PFC/rectification part of a power supply.

Something lower voltage?  (5, 12, 48, etc?)  Going to be spending a lot on copper wire.

[filssavi]

The more expensive breaker /fuses ok that is a disadvantage. I fail however to see how detecting a DC ground current with modern technology is significantly harder than with AC, it could be more expensive I give you that but not that much harder

and not having rectifiers/PFC stages can save quite a lot of energy, granted there is little power lost in each device but you could eliminate them from the vast majority of electronics on earth, so the tiny contributions start adding up fast.

However the real problem is that a switch would be way too expensive (basically we are talking of replacing almost the whole distribution grid at once), so it will never happen

[rstofer]

The only switch that would kind of make sense with the current state of power electronic would be to switch from AC to DC for distribution, not regular transmission, there AC is still going strong for now.

The great majority of loads right now (I don't have numbers but I bet is over 80% of the total residental and small industrial installed power) rectify the AC to DC anyway, and especially in residential use the conversion efficiencies are quite low.

switches will get bigger but they are being replaced by semiconductors anyway
Circuit creakers will get bigger, but it is not the end of the world

Unfortunately this will probably never happen since the costs would be way to high and so we will keep 240V/50Hz or 120V/60Hz forever I think

Actually, DC transmission is done extensively in Europe and makes a lot of sense.  But transmission is easy, it's usually just about point to point and both ends can agree on the voltage.

https://en.wikipedia.org/wiki/High-voltage_direct_current

Distribution is usually at some intermediate voltage (say 12 kV just to pick a number) and this is what is in the ground or on the poles.  Somehow we need to get that down to a low voltage that is suitable for residential use and that takes transformers of one kind or another.  With DC that is just about impossible (actually, it may actually be impossible) and that's why we need AC in distribution and utilization.

Don't bet on residential as being primarily DC capable.  My HVAC system won't run on DC.  Nor will any of my ceiling fans or even the microwave.  The stove and oven (seldom used) could possibly be DC as could lighting.  But a high percentage of my bill comes from cooling.

In most ways, I would rather we have the system they have in Europe where they get 3 phase 240/415 (or something similar) because we could then use 3 phase motors.  But I would prefer we stay at 60 Hz.

None of which is going to happen any time soon.

[rx8pilot]

In Japan, they use metric volts.

Short and misplld from my mobile......

[filssavi]

I Know full well of HVDC however it is used only for transmission not distribution,and in particular  the biggest transmission lines are hvdc(basically the ones tying multiple grids together) as the conversion station are extremely expensive, also the voltage is much higher 500 to 800 kV

the distribution grid (Medium voltage and lower) are exclusively AC and they will stay so for the forseable future (transformers there are still the king of the hill)

as for appliances, you would have been right 20 years ago, however now in europe everything (apart from the cheapest chinese crap) is inverter fed, from whasing machines, to expecially AC units, the older on/off type are getting more and more difficult to find.

so to run motors you first take AC rectify it to DC and then syntethyze AC back up. direct 50 Hz machines are already disappearing, especially the single phase ones (that are the worst anyway), this is mostly to get AAA++ efficiency rating, that consumers are quite sensitive on

for the same reasons induction machines will be slowly (again slowly) be replaced in most applications by synchronous machines, BLDC/PMSM for the high end, and synchronous reluctance for the low end

[bsfeechannel]

Not as exciting as what they do in Brazil!

What do they do in Brazil?

https://www.worldstandards.eu/electricity/plug-voltage-by-country/brazil/ ?

Well, blame Canada! Literally. 

The two standard voltages used in Brazil are the result of the history of its electrification, which started in the 19th century. Back then, as anywhere else in the world, electrification was carried out by many small private companies, each with their own standard voltages and frequencies.

127V roughly reflect the places that were electrified first. And many of them were serviced by the, then Canadian-owned, São Paulo Railway, Light and Power Ltd., popularly known simply as Light, with its 110V standard. Up to this day people  refer to 127V installations by calling them 110 installations.

Other regions were electrified by different companies a little later with 220V (phase-neutral).

Up to the 60s there were two frequencies, 50 and 60Hz. Now the standard is 60Hz.

If Light's standard back then was 110V, why 127V now? Well, there were other "standards": 100, 115, 117 and 120V. 127V is a compromise solution that's easy to obtain from a 220V three-phase Y circuit (220V ≃ 2* 127V * sin(60°) ). So most places where you have 127V (phase-neutral), you can also have  two-phase 220V (phase-neutral-phase) or three-phase 220V with a neutral.

Why don't Brazilians standardize 220V, once and for all? Because they spent all their money converting their units to the metric system.   

[boffin]

And of course, there were also some system voltages that simply died out over time. Isn’t there still some weird low-frequency AC in some parts of USA for industry or something?

You mean like Switzerland's (and also Austria's and Germany's) 15 kV, 16.7 Hz railway overhead wire voltage?

Railways are wonderfully unstandardized, The UK for example uses
25kV @ 50Hz (overhead)
750V DC (3rd rail)
1500V DC (3rd rail)
630V DC (3rd/4th rail +420/-210)

Gets even worse when you get to Spain which not only has differing voltages, but even differing rail gauges

[Gyro]

Electrolytic corrosion can be another issue for DC distribution. For instance, the London Underground uses the insulated center 4th rail as the return path for DC traction current rather than the running rails (as is done on above ground systems). This was done to prevent electrolytic corrosion of the surrounding pipes and cabling (mostly pipework I suspect).

[GeorgeOfTheJungle]

Why don't Brazilians standardize 220V, once and for all? Because they spent all their money converting their units to the metric system.   

... When British Imperial was better, halve something again and again to get exactly 1/2, 1/4, 1/8, 1/16, 1/32 etc. It's soo much easier than dividing by ten!

[jmelson]

Niagara Falls used to generate 25 Hz and parts of New York City continued using it up until the early 2000s.  I'm pretty sure it is gone now since the hydro plant stopped making it in 2006

This was sent a lot farther than New York.  We had a converter station in St. Louis, MO that created ~60Hz from the 25 Hz Ontario Hydro power, for use in large downtown buildings.  They also apparently used the 25 Hz directly for elevators, etc.  This was in use into the 1980's at least.  The May company (department store chain) had a data center there that was fed from THREE different substations, and the wild ground potentials caused all manner of trouble, including cables that got too hot to touch, and people getting knocked to the ground when plugging or unplugging cables.

Jon

[Benta]

The real reason that Japan has 100 V is fascinating and has nothing to do with technical reasons, but in fact mirrors the electrical history of Europe and the US in the early 1900s where consumer electricity started becoming prevalent.

In those days, electricity was supplied by local utilities, who also supplied lamps and other electrical goods to consumers. Every utility had their own plugs and voltages to avoid competition. There was DC, AC, different frequencies etc.
In the US, this was relatively quickly conglomerated under a few large companies, eg, Edison, and standardization took place to a large extent.
In Europe, the same thing happened, although somewhat later in the '20...'30s, where electricity supply became a national issue. Still, foreign competition was unwanted, which resulted in every European country having their own mains plugs and often different voltages, eg, 110, 220, 240 V.
Same thing with Japan. We're talking the early years of Japanese industrialization here, and overseas competition was extremely unwelcome. By choosing 100 V, Japan was certain that no overseas lamps or bulbs would work on their grid.

Protectionist times; alas, it seems they're coming back.

[schmitt trigger]

Thanks for all your replies.

Indeed, voltage selection is a little arbitrary, but most countries have somehow standardized to either of the two major standards.
But Japan, perhaps to provide a competitive advantage to its own home industry, kept the slightly odd voltage.

[tkamiya]

I have an electrician's license from Japan.

Despite that, it was never mentioned why 100 volt.  To me, 115 volt, 120 volt, and all that other voltage seems odd.  100 seems a good round number to me.  Makes calculations easier.  Also, typical single apartment feed is 20amp.  Homes may be little higher like 40amp.  We only have one or two circuit breakers.  All heavy duty appliances are gas or kerosene.  At least back when I was there in 80s, air conditioning was not common.  Power consumption and transmission from technical stand point weren't a big deal to me.  Besides, power feeds to poles were either 3300 or 6600 volts, depending on height of the pole.  Pole pigs converted them down right near our house.

[6PTsocket]

And then we sort of snuck up to 120. A lot of old stuff was 110 and then 115 or 117. In the real World in the US , today it is a few volts higher than 120 in some places

Sent from my SM-G900V using Tapatalk

[glarsson]

In a couple of years the US will have reached 230V. This stepvise increase is a trick to fool everyone into the new world order.

[6PTsocket]

The only switch that would kind of make sense with the current state of power electronic would be to switch from AC to DC for distribution, not regular transmission, there AC is still going strong for now.

The great majority of loads right now (I don't have numbers but I bet is over 80% of the total residental and small industrial installed power) rectify the AC to DC anyway, and especially in residential use the conversion efficiencies are quite low.

switches will get bigger but they are being replaced by semiconductors anyway
Circuit creakers will get bigger, but it is not the end of the world

Unfortunately this will probably never happen since the costs would be way to high and so we will keep 240V/50Hz or 120V/60Hz forever I think

That mught be OK in a switching power supply that rectifies as a first step but any low voltage DC device with a linear supply would need an inverter to go back to AC to step it down or up for higher voltage. It is the ability to transform voltages to different  values, like down from high tension transmission  lines, with low IR losses, that helped doom DC transmission, in spite of Edison killing a lot of animals and inventing the electric chair to demonstrate the dangers of AC.

Sent from my SM-G900V using Tapatalk

[basinstreetdesign]

Niagara Falls used to generate 25 Hz and parts of New York City continued using it up until the early 2000s.  I'm pretty sure it is gone now since the hydro plant stopped making it in 2006

This was sent a lot farther than New York.  We had a converter station in St. Louis, MO that created ~60Hz from the 25 Hz Ontario Hydro power, for use in large downtown buildings.  They also apparently used the 25 Hz directly for elevators, etc.  This was in use into the 1980's at least.  The May company (department store chain) had a data center there that was fed from THREE different substations, and the wild ground potentials caused all manner of trouble, including cables that got too hot to touch, and people getting knocked to the ground when plugging or unplugging cables.

Jon

More than Niagara Falls.  When I worked in a (failing) gold/copper mine in South Porcupine, ON near Timmins in Northern Ontario in 1971, half the place was on 25 Hz and half was on 60 Hz.  They had an electrical plant that was very impressive with 25 Hz rotating machines sunk halfway into the floor.  Even then they were as tall as me.  They rotated at something like 125 RPM.  There was a famous light bulb there running on 25 Hz that had been in service since the middle 1920's.  The whole place is gone now.  Just before the surface mill was to be torn down the local librarian/historian was invited to come, take anything he wanted to preserve.  He was given all of 24 hours.