0.707; and (c) and I
displaced 90°, 90° and p.4
Phase relationship a. Current
A has value 4A, and current value 3A, leading 90°. circuit containing inductance, such motor discharge light-
ing circuit, the current often reaches its maximum value after the volt-
age, which means that the current and voltage are out phase with each
other, shown Fig. 0. waveform: (a) and phase, phase angle and power
factor cosφ (b) and displaced 45°, 45° and p.3
The phasor addition currents and B.f. 10.5, where drawn to
Phasor B
Phasor A
4 units
5 units
3 units
Resultant phasor
FIGURE 10.
Alternating current series circuits
In circuit containing resistor and inductor connected series shown
in Fig. Choose a
scale of, for example, 1cm and draw the phasors scale, that 4cm and 3cm,
leading 90°. Fig.c. The phase difference, measured degrees
between the current and voltage, called the phase angle the circuit,
and denoted the symbol the lower-case Greek letter phi.
When circuits contain two more separate elements, such RL, or
RLC, the phase angle between the total voltage and total current will be
neither nor 90° but will determined the relative values resistance
and reactance the circuit. circuit the voltages must added
by phasor addition.
.4(b).5, the current will flow through the resistor and the induc-
tor causing the voltage dropped across the resistor and be
dropped across the inductor. 10.
V
I
(a)
V
I
(b)
V
I
(c)
Example
Find phasor addition the combined effect currents and acting circuit.5 the phase angle between applied
voltage and current some angle φ.3.Baisc Electrical Installation Work
198
FIGURE 10.4(a).
PHASE ANGLE φ
In a. circuit containing resistance only, such heating circuit, the
voltage and current are phase, which means that they reach their peak
and zero values together, shown Fig. 10.
The magnitude the resultant phasor can measured from the phasor diagram and is
found acting phase angle about 37° leading therefore say that the
combined effect currents and current angle 37° leading A. 10.c.c.c. The result shown Fig. 10.f. 10.
In a. The sum these voltages will equal the
total voltage but because this a.We usually assume phasors
to rotate anticlockwise and the complete diagram will shown Fig
