Why Is 3-Phase Power 380 Volts and How Are the Voltages Distributed?

Hello

I have a trivial question :)

how many volts are on 3 phases and why is 380 volts

the answer does not need to be detailed.

between individual phases and 0 is 220V (now 230V), while between the phases is 380, the phases are shifted by 120 degrees, 220 * square root of 3 = 380 (now 230 * square root of 3)

Currently it is 400V, professionally 0.4kV in the LV network (phase-to-phase voltages are rated voltages).

The picture explains a bit.

RMS values are shown here, the image is just such a "freeze frame" to show the nominal values (obviously the phase-to-phase voltage is also a sine wave).

Phase voltage is the voltage between one phase and earth.
Interfacial tension is, as the name suggests, the voltage between two phases.

In vector form (phasor diagram) it looks like this:

Drawing "on the spot", so forgive the inaccuracy. :wink:

And the phase voltages are shifted because this is the structure of the generators. As the rotor rotates, it generates phase voltages successively over time. It is obvious, is it?

It's all about the topic.

Drawings made "by peasant reason", so they should help completely "green" people.

Thank you for your answer

You could ask one more question: why in the network, the frequency is 50Hz?

The frequency is determined by the rotation speed of the generator.
Turbogenerators rotate at 3000 revolutions per minute (i.e. 50 times per second = 50Hz).

PS
50Hz can be generated at lower rotational speeds (generators in hydropower plants), but this requires a different (more complicated) generator design (specifically its rotor).

You might still ask why 220V ~, why 3 phases, why the angle between phases 120 degrees ...

220V ~ was based on the assumption that the voltage should not drop below 200V ~, and 10% of this may be losses on the line
(now they did 230V ~ - but rather they did not increase the assumed losses to 15%, but rather decreased to 10V).

3 phases ... as if to make two in out-of-phase, it cannot power an asynchronous motor, because it will not be created
rotating magnetic field; you could give two offset 90 degrees, but that causes a large flow
neutral conductor currents; minimum to obtain a rotating field without current in the neutral conductor, is
3 phases with 120 degree angles - so simply "minimalist" design, why more wires?

And why 50Hz ... the higher the frequency, the greater the losses on transmission lines, the smaller, the more
higher costs of transformers and losses on them - some compromise had to be made, the USA chose 60Hz,
Europe 50Hz - a bit strange, because in the US they probably have longer lines - maybe better materials for transformers?