Modern homes have 2-phase service to run resistive loads like clothes
dryers or water heaters, which use a special huge socket. The service box
is 2-phase but wired for single-phase loads. Except for the dryer and oven,
which tap across 2 phases. You won't find any large inductive loads in
residential homes

Workshops, restaurants, irrigation and industrial facilities are wired for
2 or 3-phase inductive loads. many of tees appliances don't even need a
neutral wire, so you have the voltages you mention which are based on the
RMS measurement. Motors running on 2 or 3 phases have different RMS
voltages than single phase. In the discussion over the wye-delta switch,
you are switching phases going into the motor to cause a nice easy startup
on a low-impact voltage configuration, then switching over to high voltage
when the motor is up to speed. The OP mentioned this as a Rube Goldberg
device that kicked in after maybe half a second.

I recommend anyone with 3 or 2-phase workshop equipment to have a qualified
electrician wire their shop. There is a lot of abstract theory to
understand with phased power. It is all to easy to assume a switch is a
switch and wire it so it self-destructs.

-- Gnarlie

On Fri, May 16, 2014 at 3:20 PM, Vincent Dow <ianvincentdow@gmail.com>wrote:

> To Gnarlodious,
>
> Your discussion of three-phase electric motors (far beyond my knowledge)
> rings authoratitive.
>
> I don't mind "Two-Phase" for a 240V (two leg) but I have never seen that on
> any electrical equipment. I've worked on many motion picture diesel
> generators (mostly Crawfords) and they all have two settings:
>
> 240V single phase (four wire system)
> 208V three phase ( five wire system)
>
> A switch throws from one output to another.
>
> Same for electrical panels. Siemens, Murray and most every residential load
> center is marked single-phase if it has two hot lugs and two bus bars
> producing 240 volts between legs. Pretty much everyone I ever worked with
> called that single-phase. Even the Los Angeles Dept of water and power uses
> this term for a two-conductor, 240V service.
>
> Reminds me of the discussion I got into about grounding vs. bonding...
>
> vinnie
>
>
>
>
> On Fri, May 16, 2014 at 4:40 PM, Ben <syncro@gmail.com> wrote:
>
> > gramSSSS
> >
> >
> >
> > > On May 16, 2014, at 1:37 PM, Ben <syncro@gmail.com> wrote:
> > >
> > > How many gram is a pinch anyway?
> > >
> > >
> > > BenT
> >
>