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airlincoln(at)sbcglobal.n
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 Posted: Sat Feb 19, 2011 4:42 pm Post subject: AC ground prong question |
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After a recent trip to Japan, I am very glad I am building Z-13/8 that only uses 14V DC power because I realize how little I understand AC...perhaps someone can enlighten me. Questions were generated while trying to charge my laptop in the hotel. I know that Japan uses 50Hz and 100V AC power (which my AC adapter (more properly called a "transformer-rectifier" I believe) could handle according to the attached label). I also knew that most such small appliance AC adapters (such as cell phones, iPods, etc.) don't have a third (ground) prong on their male plug end. However, the AC adapter for my laptop DOES have this third prong which created a problem, since the outlets in the room had only two female receptacles (the longer "neutral" slot and the shorter "hot" slot).
The hotel provided an adapter that allowed me to plug my three prong adapter into the two prong outlet, but then I wondered "Should I even be doing this? Will sparks fly? Will my AC adapter die a slow death from undervoltage? Am I okay as long as I don't peruse the AEC forum listings while sitting in the bathtub? Does my AC adapter even need this third ground prong, and if not, why don't I just dremel it off...I mean, my cell phone charger doesn't have the ground prong, so why not?"
Someone told me that the Japanese AC current is two-phase, which seemed odd to me, but I remember in my C-130 days we had electrical buses that were single-phase AC and some that were three-phase AC so I guess a two-phase AC circuit wouldn't be out of the question....is this why there is no ground prong slot on my hotel outlet? Is the Japanese electrical grid hopelessly out of date and do thousands of people die here each year from electrocution (hard to believe)? The most likely explanation would seem to be that the Japanese system is just as safe as ours (even without ground plugs) but I simply don't understand the fundamentals of AC electricity.
Long story short...I plugged in my computer using the adapter and it worked fine...but why? Can anyone explain or give me a link to a reference that will explain all this?
Do Not Archive
Lincoln Keill
Anyone
Someone had once told me that
[quote][b]
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Feb 20, 2011 6:03 am Post subject: Re: AC ground prong question |
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Here is website that gives the voltage and frequency of countries around the world: http://users.telenet.be/worldstandards/electricity.htm
Half of Japan has 50hz and half has 60hz. Although Japan's 50hz and 100 volt power is different from the USA, it is similar enough to operate most U.S. appliances. However, there may be some sensitive devices that will not work.
The person who suggested that Japan could have two phase power is completely wrong. Two phase power is very rare and would require more than two wires. I would NOT cut off the grounding prong from a cord plug. Doing so could create a shock hazard in certain situations. Some sensitive electronic devices will malfunction without being grounded.
Joe
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Sun Feb 20, 2011 8:01 am Post subject: Re: AC ground prong question |
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Dear Lincoln (and Joe)
Joe is right. I actually designed devices to operate worldwide, and I can tell you Brazil is the worst. The voltage has been known to be from 90-250 from any outlet type! Intermittent, too! Grounds? fahgedaboutit...but it is rapidly improving.
The world seems to be "harmonizing" on 230V 50 Hz.
But to answer some of your puzzle: The neutral conductor in US systems is the white wire (the larger blade). Black is higher voltage, measured against white or ground. The green wire and the U-ground is attached to the white at the main transformer, but the green is also attached to any metal "likely to be energized in a fault condition." So you see, the ground and white wire are both "neutral" in a sense, but the green ground is for safety.
If you are plugging in a device that has "no metal likely to become energized in a fault condition", and you stay out of the water, then you are good to go with only two prongs. Since this condition is usually hard to know with 100% certainly, three is always a better choice.
But be aware: Worldwide 230 VAC 50 Hz outlets do not have the neutral and ground connected anywhere.
For additional credit: Q: Should the "face" on the US plug be installed right-side up or upside-down? A: The socket should be installed so that upon the inadvertent extraction of the plug (getting yanked out), The U-ground connection is the last prong to be disconnected. This usually means that plugs near the floor should have right-side-up faces, plugs way up high should have upside down faces. Cool huh?
Also, be aware that everyone makes mistakes. In the Southwest, Mexican construction plumbers work for peanuts. "C" in Mexico is "Caliente" (hot) and an "F" looks like an "H" if you are illiterate.
I have seen branded, UL, CSA, ETL approved, where grievous errors were not caught.
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Eric M. Jones
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