Hioki 3196 - Page 228

Appendix
222
Unbalance fac-
tor of three-
phase current
The current unbalance factor is several times larger than the voltage
unbalance factor. The less a three-phase induction motor slips, the
greater the difference between these two factors. Voltage unbalance
causes such phenomena as current unbalance, an increase in tem-
perature, an increase in input, a decline in efficiency, and an increase
in vibration and noise.
Displacement power factor (DPF)
The power factor (PF) is the ratio of active power to apparent power.
An inductive load delays the current behind the voltage, and a capaci-
tive load advances the current ahead of the voltage.
PF (power factor) 0 < PF < 1 There is reactive power, which is the power supplied but
not consumed.
PF = 1 All the supplied power is consumed, and there is no
reactive power.
PF = -1 The power, voltage, and current are generated in phase.
-1 < PF < 0 Phase lead or phase delay of the power and current is
generated.
In general, a power factor is calculated using all effective values, and
harmonic contents are therefore included. In addition to this power
factor (PF), the displacement power factor (DPF) is the ratio of active
power to apparent power. However, the displacement power factor
(DPF) is described using the cosine of the phase difference between
the fundamental wave current and the fundamental wave voltage and
does not include the harmonic contents of voltage or current.
DPF (displace-
ment power fac-
tor)
0 < DPF < 1 The current phase is ahead of or behind the voltage
phase. Equipment consumes power.
DPF = 1 The current and voltage are in phase. Equipment con-
sumes power.
DPF = -1 The current and voltage are in opposite phases. Equip-
ment produces power.
-1 < DPF < 0 The current phase is ahead of or behind the voltage
phase. Equipment produces power.
The displacement power factor is the same as the power factor in
watt-hour meters used in ordinary homes, and also the same as the
power factor calculated using the true reactive-power-meter method
used in 3196. If the displacement power factor is low (the current is
behind the voltage), add a phase-advancing capacitor to the electric
system for correction. In general, a displacement power factor is used
in an electrical system, and a power factor is used in equipment. In
one neighborhood, the power factor shows a larger value than the dis-
placement power factor.