The study of three-phase electricity*
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I remember in junior high school physics class, when we first started learning about alternating current, the teacher said that the 220V supply voltage is alternating current, with its direction and magnitude changing constantly. But for the sake of simplifying calculations, we treat it as equivalent to 220V direct current, and this does not affect the results of our analyses and calculations. It is precisely because of such assumptions that there are series and parallel circuits for single-phase electricity. So why can’t we make such assumptions about three-phase electricity? Doing so complicates three-phase circuits, making them harder to understand and causing confusion, as in the cases of star connection and delta connection, for example. . .
Phase voltage and line voltage: In alternating current, phase voltage refers to the voltage between any phase wire (live wire) and the neutral wire, which is 220V. Three-phase alternating current has three phase voltages: all three have the same voltage and frequency, with a phase difference of 120° between them. The voltage between any two phase wires is called line voltage, and it is 380V. Three-phase alternating current has three phase voltages, and therefore three line voltages as well: the voltages of these three line voltages are identical in terms of voltage and frequency, with a phase difference of 120° between them. The line voltage equals (√3) × phase voltage. In a three-phase four-wire power system, the voltage between any two of the three phase wires is called the line voltage, while the voltage between a phase wire and the neutral wire is called the phase voltage. The phases of the three phase voltages differ by 120 degrees. The line voltage is the vector sum of the phase voltages of two phases, and the relationship between the line voltage and the phase voltage is such that line voltage = √3 times the phase voltage. For mains electricity, the phase voltage is 220V, while the line voltage is √3 times 220V, that is, 380V.
The moderator explained it in great detail; thanks for sharing!