How are the power consumption and the power factor of a 3-phase motor calculated?
Most 3-phase compressor motors are wired as “Y-Connected Load.” To determine power factor and power consumption, nine different values must be measured while the compressor is running: We will need to measure nine (9) different values of the compressor while running : EL = The average line voltages between phases 1-2, 1-3, and 2-3 Vp1 = Voltage between Phase 1 and neutral Vp2 = Voltage between Phase 2 and neutralVp3 = Voltage between Phase 3 and neutral Ap1 = Amperage through Phase 1 Ap2 = Amperage through Phase 2 Ap3 = Amperage through Phase 3 The True Power (Pt) can be calculated several ways. Two of which follows. 1) Pt = 0.6 x [(Vp1 x Ap1) + (Vp2 x Ap2) + (Vp3 x Ap3)] 2) Pt = 1.039 x EL x (Ap1 + Ap2 + Ap3) / 3 The power factor is always 0.6 (lagging) for a Y-Connected Balanced Load. Therefore, the Volt Amps (Volts x Amps) will always be 1.67 times greater than the true power.
