Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ncar!boulder!sunybcs!bingvaxu!leah!itsgw!batcomputer!cornell!rochester!pt.cs.cmu.edu!andrew.cmu.edu!sj1f+ From: sj1f+@andrew.cmu.edu (Steven Kent Jensen) Newsgroups: sci.electronics Subject: Re: How are power line voltages determined? Message-ID:Date: 11 May 88 02:08:38 GMT References: <5770004@hpscdc.HP.COM> Organization: Carnegie Mellon Lines: 8 In-Reply-To: <5770004@hpscdc.HP.COM> The funny 117 comes from the fact that AC voltage is not constant, it varies as a sine wave. Therefore the root-mean-square (basically the average of the absolute value) voltage is the peak voltage divided by the square root of two. peak voltage on normal lines is about 165V. As to the other numbers, I do not know why there is a shift (I can see rounding 117 to 115 or 120, but not 110). Steven Jensen