1–2
EPM 6010 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
CHAPTER 1: THREE-PHASE POWER MEASUREMENT
FIGURE 1–1: Three-phase Wye winding
The three voltages are separated by 120
o
electrically. Under balanced load conditions with
unity power factor the currents are also separated by 120
o
. However, unbalanced loads
and other conditions can cause the currents to depart from the ideal 120
o
separation.
Three-phase voltages and currents are usually represented with a phasor diagram. A
phasor diagram for the typical connected voltages and currents is shown below.
FIGURE 1–2:
Three-phase Voltage and Current Phasors for Wye Winding
The phasor diagram shows the 120° angular separation between the phase voltages. The
phase-to-phase voltage in a balanced three-phase wye system is 1.732 times the phase-
to-neutral voltage. The center point of the wye is tied together and is typically grounded.
Ia
Vbn
A
B
C
Van
Vcn
N
Van
Vcn
Vbn
Ic
Ib
Ia
