That being said, in household use the per-household balancing between the phases is usually very poor (e.g. all lightning on one phase). Overall the balancing turns out ok across the grid, but the meter doesn't see that. So this is a very relevant condition for household meters.
Even in apartment buildings, each apartment has its own meter, almost always single phase.
Also, most overhead transformers I have seen are entirely single phase. Often you will see a bank of 3 single-phase transformers if a customer requires 3 phase service. Larger customers are connected to a pad-mounted 3-phase transformer connected to the primary overhead service through an underground dip from the pole.
In the US most homes are just tapped to 1 phase, if there are 3 on the pole.
Loads that span all 3 phases are generally motor loads that will benefit from the rotating magnetic field that 3-phase service provides -- such as pumps and compressors.
3 phase power to residential is rare in the US.
Residential power in North America is usually delivered as "split phase", +120V, neutral, and -120V. (180 degrees out of phase: https://www.youtube.com/watch?v=vOh2OSJ44eE) The voltage across the two hot conductors is 240V, which is used for big stuff. You get it by tapping a transformer in the middle of a coil: https://en.wikipedia.org/wiki/Split-phase_electric_power
Three phase power has three hot conductors, 120 degrees out of phase to each other. In the US it can be delivered at a bunch of different voltages, depending on what transformer the customer installs, but generally I worked with 277/480. (277V hot to neutral, 480V hot to hot. Generally all commercial lighting runs on 277V.)
And to be specific, three phase is primarily useful because motors that use it are self-starting, you don't need to capacitor-and-switch arrangement single phase motors use, which frequently break. Less important now that most big motors use VFDs. Also, supposedly due to some frequency voodoo you don't need to use as much cable when running three phrase transmission cable.
As to the benefit to motors, it was my understanding that using split-phase or a single phase and a capacitor creates a less-than-optimal magnetic field which results in more noise/vibration and wear on the motor as opposed to 3 phase.
This setup is pretty much a mess, and can wreak havoc on laboratory setups, so e.g. at universities all the lab rooms are laid out with TN (the standard everyone else uses). This means you can mess stuff up in the lab by running an extension cord from the adjacent non-lab room (e.g. get large ground voltage differences, all sorts of wanky stuff).
The cooker should never be connected to a normal kitchen ring main.
> Q1.18 Appendix 15 of BS 7671: 2008 gives advice on ring final circuits and sharing/spreading the load around the circuit. Item (iii) suggests that cookers, ovens and hobs over 2 kW should be on their own dedicated circuit. Why can’t ovens of less than 3 kW be connected to a ring final circuit via a suitable connection point such as a socket-outlet or fused connection unit?
> Appendix 15 is intended to give guidance only. Such connection is not prohibited, provided that no part of the ring final circuit will be overloaded as a result.
> Regulation number(s)
> 433.1.5
So, not forbidden, but if you have new wiring the electrician is going to give the cooker its own circuit.
I'm trying to google a diagram, but I only find a bunch of forum posts that explain. For Neff stuff (the one we have), the connectors are numbered 1, 2, 3, 4 and 5.
1-2-3 would be separate phases in a 3-phase home and joined together for a single phase.
https://www.diynot.com/diy/threads/neff-hob-t1-k40x2-wiring-...
> Most European transformers are three-phase and on the order of 300 to 1000 kVA, much larger than typical North American 25- or 50-kVA single-phase units.
Systems which run a higher consumer voltage (e.g. 230V) will tend to use higher kVA transformers compared to the American system (~110V).
I believe this is because it is feasible to run longer cables when using higher voltage (higher voltage -> lower current -> lower thermal losses per metre of cable), hence it is economical to use fewer, larger transformers in a higher voltage system vs. a lower voltage system.
However, even here the network transformers do get three-phase.
Figure 3 of [1] is puzzling. They claim to be testing a 3-phase meter, but the circuit shown is single-phase. Are they testing 3-phase meters with only one phase connected? That's way out of balance; 3-phase systems normally have at least roughly equal loads on each phase. While a 3-phase meter with an wildly asymmetrical load ought to measure accurately, that's not a normal condition.
[1] http://doc.utwente.nl/102016/1/Runaway_energy_Meters.pdf [2] http://ieeexplore.ieee.org/document/7866234/