BBH Report Home Page
October 8, 2002 Provided by System Dynamics Inc.

Your Voice -- Readers' Comments

A few of YOUR thoughtful tidbits culled from this months' email.

Mike Tritt wrote from New Zealand: "The New Zealand and US power systems are different, particularly because of the voltage (230v vs 110) but also in the way that street transformers are arranged and electrical practices have developed. Some of the standards and products developed and in use in the US may not be compatible with our system and I'm wanting to invstigate these differences. Can you clarify your comment "HomePlug crossed AC phases very well".

We replied "North American homes usually have what is called "single phase three-wire 120/240 Vac" - dual 120V / 240 V RMS with the lower voltage used for wall sockets and the higher voltage for major household appliances. The service panel has two 120V main circuits with a common return/ground; the two circuits are 180 out of phase. Combining the circuits provides 240 VAC. In the typical main electrical panel or "load center", rows of circuit breakers alternate between the two main circuits, often called "phases"; dual breakers are used for 240V circuits."

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