On Tue, 13 Sep 2005 18:56:34 +0900, Brenda Ann wrote:

Voltages in Saudi Arabia are nominally the same as on the North American
continent. This is to say, 127 volts for most appliances, 220 volts for
heavy appliances. Both at 60 Hz line frequency.

Sounds to me, an electrical power engineer, that they are using a
three-phase 220V (nominal) secondary distribution, with 127 V
provided by phase-to-neutral and 220 V provided by phase-to-phase.
The neutral is not derived from a center-tap on the phase-to-phase
secondary (which is really single-phase if only two phase leads are
provided) but is "carried through" from a three-phase wye
arrangement.

Although this is fairly common in US commercial d industrial
occupancies (277/480V is more common) where the lower voltage is
used for lighting and the higher voltage used for machinery, it is
not permitted in the US for residential occupancies, and IIRC there
are severe circulating third-harmonic current problems if the
secondary is a delta rather than a wye.

This is entirely different from a single-phase 220V center-tap
secondary distribution which is standard in North America.

--
73 de K2ASP - Phil Kane