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......