If the current lags the voltage shown Fig.6, the p. 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. Figure 10. cos R
T
φ
R
Z
V
V
The electrical power circuit the product the instantaneous values of
the voltage and current.f.
.f.Alternating current theory and electrical machines
201
For (a):
X
fC
X
C
C 6
1
2
( )
1
2 50Hz F
53. 10. 10. circuit voltage and current are phase.
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.5, say that the p.) defined the
cosine the phase angle between
the current and voltage.f.c.8 shows the voltage and current waveform
for pure inductor and pure capacitor. circuit the power consumed given the product the volt-
age and current, because d.
Power
Power
I
I
V
V
Pure inductor
Pure capacitor
FIGURE 10. The power waveform obtained from
the product and every instant the cycle.8
Waveform for the a.f.f. 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.03A
∴
Ω
Power and power factor
Power factor (p.05
π
Ω
∴
π
Ω
For (b):
Z X
Z
2
2 2
( )
(100 (53. From the trigonometry the impedance triangle shown
in Fig. also equal to:
p. 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.) defined the cosine the phase angle between the
current and voltage:
p.2
Ω
∴ Ω
Ω
For (c):
I
V
Z
I
(A)
230 V
113.05 113.7, p. cos
φ
Definition
Power factor (p.f.f. is
said leading.2
2. is
lagging, and the current leads the voltage shown Fig. power purely inductive
and purely capacitive circuits.c.c. Inductors
store energy magnetic field and capacitors electric field
