Three phase power into private homes is very rare. If you have all three phases it's generally to run large motors, which are much more efficient with three phrase running (and I don't think single phase motors get above a certain size anyway). The biggest motor in most houses would be the air conditioner compressor and unless you are filthy rich and live in a mansion even that is normally not that large. If you own a farm, though, it's another matter.
Normally two of the three phase wires come into a home. Across the two, it's 220 v (nominally) and is used for high-amperage appliances such as stoves, ovens, water heaters, air conditioners, and dryers. From either to neutral is 110 v (again nominally) for lighting and other general purpose uses - and the circuits are divided as evenly as possible between the two. The above is valid for the USA and Canada, at least. When I lived in San Francisco we had a 100 amp house service. But then we had gas water heat and no need for an air conditioner. Wonder how it's done in the UK and other 220-240 v countries. Carleton -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Phil Chernack Sent: Tuesday, February 03, 2004 12:36 To: U.S. Metric Association Subject: [USMA:28492] Re: Torque and horsepower Marcus, Power is usually given in amps because it is easier to calculate the load on a particular breaker in your house this way. For instance, if I have a 15 amp circut and I put a 3 amp appliance on it, I know my remaining draw before blowing the circut is 10 or so amps (allowing for a margin of safety). If power was given in watts only, I would have to divide watts by volts to get the amperage draw. BTW, most, if not all appliances give the wattage as well. Remember, American homes have 3 phase power coming into them. One bus at 220 divided into 2 at 110 each. The total amperage provided is usually around 200. Phil -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Ma Be Sent: Tuesday, February 03, 2004 12:19 PM To: U.S. Metric Association Subject: [USMA:28491] Re: Torque and horsepower Dear John, I think I could answer some of your questions below (they're interspersed). On Mon, 2 Feb 2004 18:49:56 john mercer wrote: >Is the output of electric motors still given in horsepower? To my knowledge this is one of the few products that I see reasonably correctly quoted in the market, i.e. in W. There might be exceptions though as you found below. > I have been on some small appliance web sites and they give the power of the motors in amps. True. However, I cannot understand (for the love!...) of me why ANYONE should quote power in 'amps' (S-I-C)! Whoever does that is evidently either delusional or has absolutely no understanding of the most fundamental principles of Physics... The ampere is a unit of *current*, NOT power! >... I don't know if Kilowatts would ever be excepted in North America, because everybody uses horsepower all the time... Who knows? As long as the populace continues to treat measurements in general as some "cultural" aspect in their lives we'll continue to experience and see such nonsense in the marketplace, what can I say?... Marcus ____________________________________________________________ Get 25MB of email storage with Lycos Mail Plus! Sign up today -- http://www.mail.lycos.com/brandPage.shtml?pageId=plus
