Relasyon sa mga Voltage ug Current sa Line ug Phase sa usa ka Star Connected System

Arangin ang relasyon sa pagitan sa line ug phase currents ug voltages sa usa ka star connected system, kinahanglan natong i-draw ang balanced star connected system.

Suppose due to load impedance the current lags the applied voltage in each phase of the system by an angle ϕ. As we have considered that the system is perfectly balanced, the magnitude of current and voltage of each phase is the same. Let us say, the magnitude of the voltage across the red phase i.e. magnitude of the voltage between neutral point (N) and red phase terminal (R) is VR.
Similarly, the magnitude of the voltage across yellow phase is VY and the magnitude of the voltage across blue phase is VB.
In the balanced star system, magnitude of phase voltage in each phase is Vph.
∴ VR = VY = VB = Vph

Alam nato nga sa star connection, ang line current sama sa phase current. Ang magnitud niini nga current sama sa tanang tulo ka phases ug sabihin nato nga IL.
∴ IR = IY = IB = IL, Where, IR is line current of R phase, IY is line current of Y phase and IB is line current of B phase. Again, phase current, Iph of each phase is same as line current IL in star connected system.
∴ IR = IY = IB = IL = Iph.

Ngayon, sabihin nato nga ang voltage sa R ug Y terminal sa star connected circuit is VRY.
The voltage across Y and B terminal of the star connected circuit is VYB<!–
The voltage across B and R terminal of the star connected circuit is VBR.
Gikan sa diagram, makita nato nga
VRY = VR + (− VY)
Similarly, VYB = VY + (− VB)
And, VBR = VB + (− VR)
Ngayon, tungod kay ang angle sa pagitan sa VR ug VY is 120o(electrical), ang angle sa pagitan sa VR ug – VY is 180o – 120o = 60o(electrical).

Thus, for the star-connected system line voltage = √3 × phase voltage.
Line current = Phase current
As, the angle between voltage and current per phase is φ, the electric power per phase is

So the total power of three phase system is

Source: Electrical4u.

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