The power waveform obtained from
the product and every instant the cycle.f.c.
In electric circuit more power taken from the supply than fed back
into it, since some power dissipated the resistance the circuit, and
therefore:
P )
In any d. cos R
T
φ
R
Z
V
V
The electrical power circuit the product the instantaneous values of
the voltage and current.f.c. is
said leading. When con-
sidered over one complete cycle, the positive and negative portions are equal,
showing that the average power consumed pure inductor capacitor is
zero.f.6, the p.f. cos
φ
Definition
Power factor (p.7, p.
Power
Power
I
I
V
V
Pure inductor
Pure capacitor
FIGURE 10. From the trigonometry the impedance triangle shown
in Fig. power purely inductive
and purely capacitive circuits. circuit voltage and current are phase.) defined the
cosine the phase angle between
the current and voltage.05 113.5, say that the p.
. can seen that the
power waveform reverses every quarter cycle, indicating that energy alter-
nately being fed into and taken out the inductor and capacitor. also equal to:
p.
If the current lags the voltage shown Fig.Alternating current theory and electrical machines
201
For (a):
X
fC
X
C
C 6
1
2
( )
1
2 50Hz F
53. is
lagging, and the current leads the voltage shown Fig.f. 10.2
2.) defined the cosine the phase angle between the
current and voltage:
p.f.05
π
Ω
∴
π
Ω
For (b):
Z X
Z
2
2 2
( )
(100 (53. Inductors
store energy magnetic field and capacitors electric field.8
Waveform for the a. circuit the power consumed given the product the volt-
age and current, because d. 10.This shows that inductors and capacitors store energy during one part of
the voltage cycle and feed back into the supply later the cycle.c.f. 10.03A
∴
Ω
Power and power factor
Power factor (p.8 shows the voltage and current waveform
for pure inductor and pure capacitor. Figure 10.2
Ω
∴ Ω
Ω
For (c):
I
V
Z
I
(A)
230 V
113
