Re: Wireless home LAN - WiFi vs Bluetooth?
On Sat, 03 Aug 2019 17:28:24 +0100
mick crane <mick.crane@gmail.com> wrote:
> On 2019-07-30 13:30, Matthew Crews wrote:
> > On 7/29/19 12:57 PM, David Wright wrote:
> >> On Mon 29 Jul 2019 at 20:43:04 (+0100), Joe wrote:
> >>> On Mon, 29 Jul 2019 10:26:14 -0500 John Hasler
> >>> <jhasler@newsguy.com> wrote:
> >>>
> >>>> They don't have to be on the same branch circuit: just on the
> >>>> same "phase"[1]. There is probably a gadget available that
> >>>> bridges the signal between phases.
> >>>>
> >>>> [1] They aren't really phases but everyone calls them that.
> >>>
> >>> They are in my country. 3-phase, 240V RMS each phase to neutral,
> >>> 415V RMS between phases.
> >>
> >> Irrelevant in a domestic setting: it's illegal to have more than
> >> one phase in an ordinary house. Houses will have one phase each,
> >> so you'll share your phase with various neighbours scattered along
> >> the street.
> >
> > How do you figure? In the US most 240V outlets are 3 phase, and
> > they are
> > relatively common. You need them for most ovens, washing machines,
> > and electric cars.
>
> I don't really understand how 3 phase motors work. Is normally wanted
> if you have some heavy equipment like a car crusher.
> As I understand each cable has 130 or something volts where the AC is
> 120 degrees out of sinc so putting a resistance between one of the
> cables and earth would give you just that ~130 volts.
> Somehow a 3 phase motor must get the feeds back in sinc so you get
> the 415 Volts.
A three-phase motor is pretty much three single phase motors with
a shared armature. The point about it is that the three magnetic
propulsive forces arrive in a definite order, so the motor is always
guaranteed to start and turn in the same direction every time.
Single-phase motors must use dodges like extra windings linked to
capacitors and even a partly short-circuited area of the ironwork
(shaded pole) in order to start up and run in a particular direction.
The three-phase motor doesn't need anything like this, so is
conceptually simpler.
Three phases allows lower currents in the cables than a single-phase
motor of the same power, and can run on three wires only, without the
need for a neutral wire. There's no need for any 'syncing'. In a
three-phase power system, the voltage between two phases is always the
single phase to neutral voltage multiplied by the square root of three.
https://www.raritan.com/landing/three-phase-power-explained
--
Joe
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