On 03/09/2018 09:00 AM, Chris Wood wrote: > When I was a LDS missionary in Japan in the 90s we were warned to not > bring alarm clocks with power cords -- they needed to use batteries. > Japan runs on dual prong 100v and most US devices work just fine but > plugged in clocks will run slow. I'm not sure the science behind it > but it's related to the power feed itself.
As said it's because of the frequency of the AC power cycle. The same issue occurs anywhere where 50Hz AC electricity is used, including all of Europe. Japan is even weirder, though, because half of country's power grid (the eastern half if I'm not mistaken) is 60 Hz using American generators, and the western half is 50 Hz using European generators. This goes back to decisions made in the very early 1900s, but it also might have to do with reconstruction after WW II. This difference between power grids makes it challenging to interconnect the grids and transfer power from one side to the other, to say nothing of consumer electronics, although I haven't seen a piece of electronics in years that can't work on either 50 Hz or 60 Hz, and on 110 or 220v. I think the reason power companies try to correct the frequency as they go is to help the grid interconnect more efficiently. There was talk in recent years of eliminating the requirement of power companies to make up lost cycles. Such a move would make electric clocks quite inaccurate, as this story shows. But clocks driven by synchronous motors are not as common as they used to be so it might not be such a big deal. When I was a teenager I had an alarm clock that plugged into the wall and it was timed exclusively from the line voltage cycle frequency. I wasn't cool enough for a digital clock radio back then, which would have been quartz-crystal driven, and so not susceptible to frequency changes. At BYU we had a large-scale, line-integrated UPS system that would adjust the power frequency to match the line frequency after line power was restored, to prevent any power problems for the computers and other sensitive electronics hooked to it. Not that computers are sensitive to the line frequency. I think it had more to do with avoiding power glitches. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
