A three-phase generating set can be connected in Y (star) or in Δ delta. The difference lies in the connection of the windings. If the generating set is connected in star, there are two possible voltages: phase voltage (VP = 230V) and line voltage (VL = 400V). ‘IL’ stands for line current and ‘IP’ stands for phase current. We can say that VL = √3*VP en IP = IP. If the generating set is connected in delta, the line voltage VL equals the phase voltage VP and IL = √3*IP.
Besides, the star configuration has 4 wires: 3 phase wires and 1 neutral wire starting from the star point. The delta configuration on the other hand, has no neutral wire.

Star:
VLine = √3*VPhase
ILine = IPhase  VL1  = VF1  - VF2
VL2  = VF2  - VF3
VL3  = VF3  - VF1
VL1  + VL2  + VL3  = 0
VL1  = 2*VF1*cos 30° = 2*VF1*3/2 = 3*VF1

The line voltage leads the phase voltage by 30°.
The line currents equal the phase currents with symmetrical charges.
The active power when connected in Y: P = 3*(VL/3)*IL*cos φ = 3*VL*IL*cos φ

Delta:
VLine = VPhase
ILine = √3*IPhase  ĪL1 = ĪP1 - ĪP1
ĪL2 = ĪP2 - ĪP3
ĪL3 = ĪP3 - ĪP1
ĪL1 + ĪL2 + ĪL3 = 0
IL1 = 2*IP1*cos 30° = 2*IP1*3/2 = 3*IP1

The line current leads the phase current by 30°.
The line voltages equal the phase voltages with symmetrical charges.
The active power when connected in Δ: P = 3*VL*(IL/3)*cos φ = 3*VL*IL*cos φ

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