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In a star-connected system the phase voltage is the line voltage divided by sqrt(3): 400 V between lines gives 230 V to neutral. Both voltages describe the same supply, which is why a three-phase distribution board offers single-phase 230 V outlets and three-phase 400 V circuits from the same cable.
Star relationships
Vphase = Vline / sqrt(3); S = sqrt(3) x Vline x Iline
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
No. In delta the phase voltage equals the line voltage, but the line current is sqrt(3) times the phase current.
They are the same system: 230 V is measured line to neutral and 400 V line to line, since 230 x sqrt(3) = 398 V.