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Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!kitty!larry
From: larry@kitty.UUCP
Newsgroups: sci.electronics
Subject: Re: 3 phase residential power
Message-ID: <2269@kitty.UUCP>
Date: Wed, 25-Nov-87 23:44:20 EST
Article-I.D.: kitty.2269
Posted: Wed Nov 25 23:44:20 1987
Date-Received: Sun, 29-Nov-87 06:46:32 EST
References: <372@intvax.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 25
Summary: Not common for residential use...

In article <372@intvax.UUCP>, davidson@intvax.UUCP (William M. Davidson) writes:
> Does anyone know why 3 phase power in not put into homes?

	It is MUCH more expensive for a utility to provide, since it requires:
(1) three primary (high voltage) wires for all serving areas; and (2) three
transformers per residence or close group of residences.
	Look at residential power lines sometime, and in many cases you will
find only ONE primary phase serving a given street or subdivision.

> The building I work in is like a small house and it has 3 phase power with
> all single phase equipment hooked up in a delta configuration.

	Ugh!  It sounds like you have the scourge of three-phase power,
affectionately called "dog leg service" by electricians.  This is an el-cheapo
three-phase service which is provided by only TWO transformers (one with
a center-tapped winding with the CT connected to ground).  One of the phases
is "open", and the entire 3-phase aspect of the service is subject to
instability.  This service is common for large farms, but is fortunately
disappearing for commercial service.  Dog leg service is generally limited
to 200 amperes because of the above instability problems.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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