Hopefully you know that if you plug a 100-127 volt electrical device into 220-240 volt mains (plug) you’re going to fry your device. Plain and simple. And if you plug your 220-240 volt device into 100-127 volt mains it’s just not gonna work (as it’s not getting enough juice).
Japan is a country divided in two – east Japan supplies electricity at 100 volts / 50 hertz and west Japan supplies electricity at 100 volts / 60 hertz, so as a result most electrical items in this country are 50/60 hertz compatible.
I found out the other day that the microwave in the house (which has been used here since 2000) was designed to only run on a 50 hertz frequency – and we’re living in west Japan which is 60 hertz. Looking around the ‘net it’s been said that basically running 50 hertz equipment at 60 hertz and vice-versa is bad. Nothing bad has happened to this microwave (yet), so I have to ask myself the question: does it really matter?