The current flowing through a 20 − μ F capacitor having terminals labeled a and b is i a b = 3 × 10 5 t 2 exp ( − 2000 t ) A for t ≥ 0 . Given that v a b ( 0 ) = 5 V , write a sequence of MATLAB commands to find the expression for v a b ( t ) for t ≥ 0 and to produce plots of the current and voltage for 0 ≤ t ≤ 5 ms.
The current flowing through a 20 − μ F capacitor having terminals labeled a and b is i a b = 3 × 10 5 t 2 exp ( − 2000 t ) A for t ≥ 0 . Given that v a b ( 0 ) = 5 V , write a sequence of MATLAB commands to find the expression for v a b ( t ) for t ≥ 0 and to produce plots of the current and voltage for 0 ≤ t ≤ 5 ms.
Solution Summary: The author describes the sequence of MATLAB commands to obtain the expression for v_ab(t).
The current flowing through a
20
−
μ
F
capacitor having terminals labeled a and b is
i
a
b
=
3
×
10
5
t
2
exp
(
−
2000
t
)
A for
t
≥
0
. Given that
v
a
b
(
0
)
=
5
V
, write a sequence of MATLAB commands to find the expression for
v
a
b
(
t
)
for
t
≥
0
and to produce plots of the current and voltage for
0
≤
t
≤
5
ms.
With the aid of a phasor diagram show that the active
power and power factor of a balanced three-phase load
can be measured by two wattmeters.
For a certain load, one wattmeter indicated 20 kW
and the other 5 kW after the voltage circuit of this
wattmeter had been reversed. Calculate the active
power and the power factor of the load.
ANS:
15 kW, 0.327
State the advantages to be gained by raising the power
factor of industrial loads.
A 400 V, 50 Hz, three-phase motor takes a line
current of 15.0 A when operating at a lagging power
factor of 0.65. When a capacitor bank is connected
across the motor terminals, the line current is reduced
to 11.5 A. Calculate the rating (in kVA) and the capa
citance per phase of the capacitor bank for: (a) star
connection; (b) delta connection. Find also the new
overall power factor.
ANS:
3.81 kvar, 70.5 µF, 23.5 µF, 0.848 lagging
A single wattmeter is used to measure the total active
power taken by a 400 V, three-phase induction motor.
When the output power of the motor is 15 kW, the
efficiency is 88 per cent and the power factor is 0.84
lagging. The current coil of the wattmeter is connected
in the yellow line. With the aid of a phasor diagram,
calculate the wattmeter indication when the voltage
circuit is connected between the yellow line and (a) the
red line, (b) the blue line. Show that the sum of the two
wattmeter indications gives the total active power taken
by the motor. Assume the phase sequence to be R–Y–B.
ANS: 11.7 kW, 5.33 kW
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Capacitors Explained - The basics how capacitors work working principle; Author: The Engineering Mindset;https://www.youtube.com/watch?v=X4EUwTwZ110;License: Standard YouTube License, CC-BY