[sci.electronics] 3 phase residential power

davidson@intvax.UUCP (William M. Davidson) (11/25/87)

Does anyone know why 3 phase power in not put into homes?

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.
The only 3-phase equipment is the heater.  If homes had 3 phase power, then
consumer products that contained motors could use the more efficient 3 phase
motors.
-- 
Forking is Fun!
William [i aM not a dweeb] Davidson 
Sandia National Laboratories (505) 846-1868
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larry@kitty.UUCP (11/26/87)

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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