Motor Loads
Induction Motors
4
49
4
Move the red test lead and the current probe to phase 2 (keep the black
test lead attached to phase 3).
Write down the value for true power reading (kW
2
). If the power factor is
smaller than 1, kW
1
and kW
2
will be different even if the load currents are
equally balanced. Note that the apparent power (kVA) is equal to the first
measurement.
5
Calculate the power factor (fill in your measurement results):
___ kW
1
+ ___ kW
2
___ kW
TOTAL
= = _____
√
√√
√3 ∗
∗∗
∗ ___ kVA ___ kVA
Example
Measured: kW
1
= 170 kW kW
2
= 68 kW kVA = 188 kVA
170 kW + 68 kW 238 kW
TOTAL
= = 0.73
1.73 ∗ 188 kVA 325,6 kVA
Poor power factor can be improved by adding capacitors in parallel with the
load.
If harmonics are present, consult with a qualified engineer before installing
capacitors. Non-linear loads such as adjustable frequency motor drives cause
non-sinusoidal load currents with harmonics. Harmonic currents increase the
kVA and thereby decrease total power factor. Poor total power factor caused
by harmonics requires filtering for correction.
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