3-Phase Equations

Typical 3-Phase Wiring Diagrams and Equations for Resistive Heaters

Definitions

For Both Wye and Delta
(Balanced Loads)

V_P = Phase Voltage
V_L = Line Voltage
I_P = Phase Current
I_L = Line Current
R = R1 = R2 = R3 = Resistance of each branch
W = Wattage

Wye and Delta Equivalent
W_DELTA = 3 W_WYE

Open 3-Phase Circuit Formulas:
Open Delta Watts = ²/₃ W_DELTA
Open Wye Watts = ¹/₂ W_WYE
Open 4-wire Wye Watts = ²/₃ W_WYE

3-Phase Wye (Balanced Load)		3-Phase Open Wye (No Neutral)
I_P = I _L V_P = V_L/1.73 W_WYE = V_L² /R = 3 (V_P²) /R W_WYE = 1.73V_LI_L		I_PO = I _LO V_PO = V_L/2 W_OWYE = ¹/₂ ( V_L /R) W_OWYE = 2 (V_PO²/R) W_OWYE = V_LI_LO

3-Phase Delta (Balanced Load) I_P = I _L/1.73 V_P = V_L W_DELTA = 3(V_L²)/R W_DELTA = 1.73V_LI_L		3-Phase Open Delta . V_P = V_L I_PO1 = I _PO3 = I _LO2 I_LO3 = 1.73 I _PO1 W_ODELTA = 2(V_L²/R )