Download PSpiceAssignments1

PSPICE Asssignments for Students Excused from Lab.
Exercise 1
For the circuit shown, use PSpice and Probe to graph the instantaneous voltage, current
and power over one cycle.
R  8
v(t ) 169.71sin 2 ft V
f  60 Hz
jX  j 6
The initial current in the inductor is given to be -10.1826 A.
The result is shown below.
1
Exercise 2
For the circuit shown, use PSpice and Probe to graph the real and reactive powers
delivered to the circuit as a function of frequency. Use the AC analysis to sweep the
source frequency from 300 Hz to 500 Hz in steps of 1 Hz and Probe to obtain one graph
showing real and reactive power supplied by the source and another graph showing
power factor as a function of frequency. Determine the source frequency for unity power
factor.
The circuit impedance is



109
800000 
(1)
Z  50  j  2 f (0.7958) 
  50  j  5 f 

2 f (198.94) 
f



The real power is
I m2
I m2
P  R  50
(2)
2
2
and the reactive power is
I2 
800000  I m2
Q  X m  5 f 
(3)

2 
f
 2
The power factor is
800000 

5f 


f

cos  cos  tan 1
(4)
50






In probe, select Plot control and Add Plot to create two graphs on the screen. Select Xaxis and set the range to change the frequency axis scale to 350 450 Hz. Using Add
Trace plot P and Q with the trace expressions given by (2) and (3).
Use Plot Control, select plot and down key to switch to the lower graph and using Add
Trace add the power factor with the Trace Expression as given by (4). Using the cursor
command you can move along the plot with the right or left arrows. The co-ordinates at
which the cursor is located are displayed on the lower right hand of the screen. You can
select between different plots by holding down the control key while pressing the right or
left arrow keys. Using the Label command you can add text, lines and arrows to the plot.
The plot produced on the probe is shown below. From the plots we see that the circuit
changes from capacitive to inductive at the series resonance frequency where reactive
power is zero.
2
3
Exercise 3
A 3-phase line has an impedance of 3 + j4 . The line feeds two balanced three-phase
loads that are connected in parallel. The first load is Y-connected and has an impedance
of 30 + j40 /phase. The second load is delta connected and has an impedance of 60 j45 /phase. The line is energized at the sending-end from a 3-phase balanced supply of
line to neutral voltage Van  2000 V (rms), 60 Hz. Determine
(a) Current in the line for each phase.
(b) Current in each phase of the Y-connected loads.
(c) Current in each phase of the delta connected loads.
1a
3  j 4
Ia
1b
2a
3  j 4
Ib
1c
2b
3  j 4
2c
Ic
3a
5
3b
3c
0
4a
4b
4c
IYa
IYb
IYc
Ibc
6
Iab
Ica
7 60  j 45
30  j 40
0
4
 10.61 mH
2 (60)
40
The Y-connected load inductance per phase is L 
 106.1 mH
2 (60)
1
The -connected load capacitance C 
 58.9463  F per phase is
2 (60)(45)
The line inductance per phase is L 
From the above results the currents are:
(a) The line currents
I a  8.00 A , I b  8.0  120 A , and I c  8.0120 A
(b) Currents in the Y-connected loads are:
IYa  3.578  63.43 A , IYb  3.578176.6 A , and IYc  3.57856.57 A
(c) Currents in the -connected loads are
I ca  4.131176.6 A , I ab  4.13156.57 A , and I bc  4.131  63.43 A
4