Currently in Japan, contemplating the purchase of a rice cooker to take back to the United States. These are labeled as “for use in Japan only”, and are designed to operate on 100V mains. There is a section of rice cookers in the store labeled “for overseas use,” and they’re all rated for 220 (i.e. China; LOTS of Chinese tourists buying electronics here). The salesperson indicated that folks from Taiwan regularly buy the 100V model to take back to Taiwan, where the mains voltage is 110V, and there has been no indication problems.
If I take a 100V rice cooker back to the US (120V mains), am I pushing the envelope a bit too much? If power scales with V[sup]2[/sup], then it’s conceivable to me that this thing could draw 44% more power than it’s designed for, unless there’s something I’m missing. The electronics are likely fed by a SMPS, which would probably tolerate a wide range of input voltages; it’s the main rice heating element I’m concerned about (BTW, this is an induction-heated model).
Thoughts? I have until 9AM EDT 6/5 to make a decision.
Which rice cooker?
Without a make and model, we can’t give more than speculation.
My own guess is that it will work without issue.
It was probably designed with use outside Japan in mind.
There are a lot of markets/potential customers that use 110-120 vac.
That it’s an induction type is a good sign since there has to be a driver for the magnetic system.
110 and 120 VAC are really the same thing. Line voltage is allowed to vary between those numbers. Much of the world uses 220-240 instead of 110-120, but there are no oddballs in between.
Frequency is clearer-cut - roughly half the world, including North America, is on 60 Hz, and half on 50 Hz. For an appliance that operates on simple resistance, though, it doesn’t matter.
Eastern Japan is 50 Hz, western Japan is 60 Hz. Most household appliances sold in Japan should be designed to work with both, but it’s definitely worth checking.
I’m sure the OP is not looking at simple rice cookers with resistance heaters. Modern high-end Japanese rice cookers are induction-heated pressure cookers. The induction heating system is generally driven by solid-state inverters.
This block diagram of a Toshiba rice cooker shows an AC/DC converter and a DC-DC buck converter feeding the heater power system. Something like this should work fine with a 120V input voltage.
The high-end models are only available in Japan. Even the fanciest Zojirushi cooker sold in the US is not as good as the ones sold in Japan.
The voltage tolerance in Japan is ± 10%. So it can be assumed a 100 V heater is designed so it can safely be powered at 110 V. But here in the U.S. the voltage can be as high as 126 V. Which means that, when used in the U.S., it’s possible the heater would be expected to produce 31% more power than the max power it’s designed for. That’s not good if the heater is powered on all the time during use, e.g. a hair dryer.
Now for the good news… the heater in a rice cooker is not on all the time. The temperature of the rice cooker is controlled by a thermostat limit sensor. It’s a simple on-off controller: when the temperature goes above a certain threshold temperature, the thermostat opens and 100 V (or 120 V) is removed from the heater. When the temperature drops below a certain threshold temperature, the thermostat closes and full voltage is applied to the heater. Lather, rinse, repeat. When the rice cooker is powered from 120 V instead of 100 V, it simply means the temperature will rise at a faster rate when the thermostat closes, and there will be a little more overshoot immediately after the thermostat opens. In addition, there’s a thermal fuse in case the thermostat sticks close.
So I don’t think you have anything to worry about.
Thanks for the info - I wasn’t aware rice cookers have gone high-tech.
So it looks like the OP is safe in either case; the rice cooker should work fine if it’s a simple design (described in my post above) or a fancy design (your description).
What the salesperson would not know is if there is a shortened lifetime by using them in Taiwan. We brought our Japanese rice cooker but then got a transformer and have used that for over five years. If the high end cooker is expensive, then it may be worth it. Looking on Amazon, there a some fairly inexpensive ones which are rated for the required wattage.
Apart from the heating elements, everything will be rated for far over the line voltage, for safety reasons. So a 100V unit will be really a 180V unit, and a 220V unit really 300. Or something like that.
So going overvoltage doesn’t mean it will fail, it just means that the margin is reduced.
Anything with a mains-connected electric motor is at risk. Refrigerators, vacuum cleaners, sewing machines. Rice cookers, not so much.
I’ve read that the 60 and 50 Hz areas of Japan share current by changing the frequency as power changes sides. How did two standards come to be in use?
Apologies for selfishly being on a vacation that afforded me very limited internet access, and even more limited time in which to use it. I’m home now, so I can more easily reply at length.
As Melbourne suggests, I’ve been reading the responses - thanks, all. In the end, we decided not to buy. “It will probably be OK” would have been fine for a cheap gadget that only gets used with close supervision, but for an expensive appliance that will operate mostly unattended, the risk of failure (or a fire) was something we just couldn’t get comfortable with.
As it turns out, there are made-in-Japan rice cookers available from Amazon here in the US. This one, according to buyers, was specifically made for use in the US. I’m not sure how that’s indicated in the packaging/documentation, and it’s entirely possible that it’s completely identical to the model we could have bought in Japan for less money, but this way we’ll at least have recourse through Amazon if there’s a problem.
