ENA Lab Manual 2k14 Spring-2016 First 7 Labs

8/18/2019 ENA Lab Manual 2k14 Spring-2016 First 7 Labs

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Electrical Network Analysis 2k14

1

EXPERIMENT 1OBJECTIVE:

Verification of Star Delta Transformation

EQUIPMENT REQUIRED: Circuit #4 of D3000 – 1.3 Electrical Networks-1 Module

Power Source

Ammeter

Connecting Wires

THEORETICAL BACKGROUND:―Star -delta transformation is a mathematical technique to simplify the analysis of an electrical

network‖

Delta Connections Star ConnectionsSituations often arise in circuit analysis when the resistors are neither in parallel nor in series.

The transformation is used to establish equivalence for networks with 3 terminals. Where three

elements terminate at a common node and none are sources, the node is eliminated by transforming

the impedances. For equivalence, the impedance between any pair of terminals must be the same for

both networks and hence the current through any pair of nodes must be same for both networks.

Delta to Y Conversion:To obtain the equivalent resistances in the wye network, we compare the two networks and

make sure that the resistance between each pair of nodes in the delta or PIE network is the same as

the resistance between the same pair of nodes in the Y (or T) network. Each resistor in the Y network

is the product of the resistors in the two adjacent delta branches, divided by the sum of the three delta

resistors. Equations for transformation from Δ-Load to Y-load are as follows:

Y to Delta Conversion:Each resistor in the delta network is the sum of all possible products of Y resistors taken two

at a time, divided by the opposite Y resistor. One may wonder why RY is less than R delta. Well, we

notice that the Y connection is like a ―series‖ connection while the delta -connection is like a

―parallel‖ connection. Equations for transformation from Y-load to Δ-load are as follows:


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CIRCUIT DIAGRAM:

Connection for Delta network:

A

Ra

Rb

Rc

V

N3

N1 N2

Connection for Star network:

A

V

R1 R2

R3

N1 N2

N3


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PROCEDURE: Connect the circuit for delta connection as shown in figure.

Note the current flowing through R a.

Repeat the same procedure and note the currents flowing through R b and R c respectively.

Note these values in the table. Now connect the circuit for star connection as shown in figure 2.

Using same procedure as described above, note the currents flowing through R 1, R 2 and R 3 respectively.

Note these values in the table.

The current through any pair of nodes must be same for both networks.

OBSERVATIONS & CALCULATIONS:Resistance:

Delta StarA & B B & C A & C A & B

B & C

A & C

Verify,

Also,

Currents:

Sr. No.

Delta Star

Voltage Ia Ib Ic Voltage I1 I2 I3

(volts) (mA) (mA) (mA) (volts) (mA) (mA) (mA)

1

2

3

PRECAUTIONS: While dealing with electric circuits handle the apparatus carefully.

Make sure the connections are tight.

Observe the readings carefully.

LEARNING AND FINDINGS:

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Verification of Maximum Power Transfer Theorem


DMM

Shorting links and connecting leads

THEORETICAL BACKGROUND:In order to achieve the maximum load power in a DC circuit, the load resistance must equal

the driving resistance, that is, the internal resistance of the source. Any load resistance value above

or below this will produce a smaller load power.

System efficiency (η) is 50% at the maximum power case. This is because the load and the

internal resistance form a basic series loop, and as they have the same value, they must exhibit equalcurrents and voltages, and hence equal powers. As the load increases in resistance beyond the

maximizing value the load voltage will rise, however, the load current will drop by a greater amount

yielding a lower load power. Although this is not the maximum load power, this will represent a

larger percentage of total power produced, and thus a greater efficiency (the ratio of load power to

total power).

Power dissipated in the load resistor R L is given by V2/ R L .When load has extreme values of

zero and infinity then power dissipated is zero. For other values of R L power reaches a maximum

value when R L is equal to internal resistance of source. When this happen load is matched to internalresistance of source.


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In both cases (a) and (b) maximum power is transferred when load resistance is equal to

source internal resistance r. That is

R L = r

Under these maximum power conditions, the potential difference across the load R L is equal

to potential difference across the potential difference across the internal resistance.

CIRCUIT DIAGRAM:

PROCEDURE: With the module power supplies switched OFF.

Connect short links 1.2 & 1.4, 1.6 & 1.7 as shown in circuit diagram.

Connect DMM at 1.5 & 1.12 which gives the open circuit voltage or no load voltage.

Set R 1 fully clockwise.

Switch on the module power supplies and note the reading of DMM (open circuit voltage) the

load resistance being infinite. Transfer the leads of DMM at 1.5 & 1.10. Insert a short link at 1.11 & 1.12.

Note the value of DMM this representing the source terminal voltage at R 1 for 1kΏ.

Adjust the value of R 1 in steps and note the value of source terminal voltage.

For each set of readings calculate the value of power dissipated in R 1 from expression V 2 /R 1

OBSERVATIONS & CALCULATIONS:

R 1 1000 900 800 700 600 500 400 300 200 100

V R1

I R1

P R1


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GRAPH:Plot graphs between a) V & I and b) R & P. Use graph paper.





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Verification of Reciprocity Theorem


DMM

Shorting links and connecting leads

THEORETICAL BACKGROUND:In its simplest form, the reciprocity theorem states that “if an emf E in one branch of a

reciprocal network produces a curr ent I in another, then if the emf E is moved from the first to the

second branch, it will cause the same current in the first branch, where the emf has been replaced by

a short circuit.”

In other words, it simply means that E (causing a current say I ) and I (caused by E in any certain branch) are mutually transferable. The ratio E / I is known as transfer resistance or impedance (Z) in

AC networks. Another way of stating the above theorem is that the receiving point and sending point

in a network are interchangeable.

When applying reciprocity theorem for a voltage source, following steps must be taken:-

Voltage source is replaced by a short circuit in original location & Current source is replaced

by an open circuit in original location.

Polarity of source in new location is such that the current direction in that branch remains

unchanged.

Two-Port Networks:Consideration of reciprocity leads naturally to two-port networks. These are networks with four

terminals considered in two pairs as ports at which connections are made. The emf E in the

reciprocity theorem is considered to be connected to one port, say port 1, while the current is at port

2, assumed to be short-circuited. The ports result from breaking into two of the branches of the

network. One terminal of each port is denoted by (+) to specify the polarity of the voltage applied at

the port, and currents are positive when they enter the (+) terminal.

The fundamental variables are V1, I1, V2 and I2. Any two of these variables are functions of the

remaining two. For certain networks, some of the four choices are not admissible. In most cases, the

variables appearing in the models are variations from DC bias conditions, not the DC variables

themselves.

A single resistor forms two two-ports, depending on

whether it is in series or shunt. For the series resistor, itis normal to take the dependent variables as I1 and I2,

and the independent variables V1 and V2. The

coefficients are called the admittance parameters, since

admittance is the ratio of current to voltage. If the

resistor is connected in shunt, the natural independent

variables are I1 and 2, while V1 and V2 are the

dependent variables. The coefficients in this case are

the impedance parameters, since impedance is the ratio

of voltage to current. In both cases, we see that the off-

diagonal or transfer coefficients are equal.

A non-bilateral and a nonlinear element, such as arectifying diode, destroy reciprocity.


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T-Network:

AE

20V

R1

R2

R3

400 ohm

800 ohm

1000 ohm

Reciprocal:

R1

R2

R3

400 ohm

800 ohm

1000 ohm

A

20 V

E

Pie Network:

A

20

R1 400 ohm

R2

800 ohm

R31000 ohmV

E

Reciprocal:

A

20 V

ER1 400 ohm

R2

800 ohm

R31000 ohm


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CIRCUIT DIAGRAM:

PROCEDURE: Connect the circuit for T-Network as shown in circuit diagram.

Vary voltage from 5 V to 12 V with the difference of 2 V and note the corresponding current

I with the help of ammeter.

Now interchange the positions of ammeter and power supply to obtain the reciprocal T- Network. Again repeat the same procedure and note current I’.

Connect the same resistances in PIE-Network and repeat the same procedure and calculate

currents I, I’.


Sr. No.T-Network PIE-Network

Voltage I I’

Voltage I I’

1 5 5

2 7 7

3 9 9

4 12 12





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Design and Implementation of RC Series Circuit for understanding of transient response,

charging, discharging and time constant.

EQUIPMENT REQUIRED: Decade Capacitor box

Decade Resistor Box

Cathode Ray Oscilloscope

Function Generator

Connecting Leads

THEORETICAL BACKGROUND:Capacitor is an electronic device, which is used to store electric charge

or electrical energy. A capacitor stores electric charge on its plates. There

are various types of capacitors available.

In its simplest form a capacitor consists of two identical conducting

plates which are placed in front of each other. One plate of capacitor is

connected to the positive terminal of power supply and the other plate is

connected to negative terminal. The plate which is connected to positive

terminal, acquired positive charge, and the other plate connected to negative

terminal. Separation between plates is very small. The space between the

plates is field with air or any suitable dielectric material. Electric charge stored between the plates of

a capacitor is directly proportional to the potential difference between the plates. Charge storing

capability of a capacitor is called capacitance ofcapacitor.

Basic RC Circuit:A basic switched RC circuit is shown in

Figure. Most of the key ideas concerning charging,

discharging and dc transients in RC circuits can be

developed from it.

Capacitor ChargingFirst, assume the capacitor is uncharged and that

the switch is open. Now move the switch to thecharge position. At the instant the switch is closed

the current jumps to E/R amps, then decays to zero, while the voltage, which is zero at the instant the

switch is closed, gradually climbs to E volts. The shapes of these curves can be easily explained.

First, consider voltage. In order to change capacitor voltage, electrons must be moved from one

plate to the other. Even for a relatively small capacitor, billions of electrons must be moved. This

takes time. Consequently, capacitor voltage cannot change instantaneously, i.e., it cannot jump

abruptly from one value to another. Instead, it climbs gradually and smoothly as illustrated in figure.


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Now consider current. The movement of electrons noted above is a current. As indicated inFigure, this current jump abruptly from 0 to E/R amps, i.e., the current is discontinuous. ( Since

capacitor voltage cannot change instantaneously, its value just after the switch is closed will be the

same as it was just before the switch is closed, namely 0 V. Since the voltage across the capacitor

just after the switch is closed is zero (even though there is current through it), the capacitor looks

momentarily like a short circuit. This is an important observation and is true in general, that is, an

uncharged capacitor looks l ike a short cir cuit at the instant of switching . Applying Ohm’s law

yields current equal to E/R amps.)

Charging equations:

Steady State Condition:When the capacitor voltage and current reach their final

values and stop charging, the circuit is said to be in steady state.

Since the capacitor has voltage across it but no current through

it, it looks like an open circuit. This is also an important observation and one that is true in general,

i.e. a capacitor looks like an open ci rcui t to steady state dc.

Capacitor Discharging: Now consider the discharge case. First, assume the capacitor is charged to E volts and that the

switch is open. Now close the switch. Since the capacitor has E volts across it just before the switchis closed, and since its voltage cannot change instantaneously, it will still have E volts across it just

after as well. The capacitor therefore looks momentarily like a voltage source, and the current thus

jumps immediately to E/R amps. (Note that the current is negative since it is opposite in direction to

the reference arrow.) The voltage and current then decay to zero as indicated.

Discharging equations:


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The Time ConstantThe rate at which a capacitor charges depends on the product of R and C and it’s known as

the time constant of the circuit and is given the symbol (the Greek letter tau). RC has units of

seconds.Thus,

=RC (seconds, s)

Duration of a Transient

The length of time that a transient lasts depends on the exponential function

. As t

increases,

decreases, and when it reaches zero, the transient is gone. Theoretically, this takesinfinite time. In practice, however, over 99% of the transition takes place during the first five time

constants (i.e., transients are within 1% of their final value at t=5

). This can be verified by direct

substitution. Similarly, the current falls to within 1% of its final value in five time constants. Thus,

for all practical purposes, transients can be considered to last for only five time constants .

Moreover larger the time constant, the longer will be the duration of the transient.

Square Wave SignalUseful wave shapes can be obtained by using RC circuits with the required time constant. If

we apply a continuous square wave voltage waveform to the RC circuit whose pulse width matches

that exactly of the 5RC time constant (5

) of the circuit, then the voltage waveform across the

capacitor would look something like this:


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The voltage across the capacitor alternates between charging up to V c and discharging down

to zero according to the input voltage. Here in this example, the frequency (and therefore the

resulting time period, ƒ = 1/T) of the input square wave voltage waveform exactly matches twice that

of the 5RC time constant. This (10RC) time constant allows the capacitor to fully charge during the

―ON‖ period (0-to-5RC) of the input waveform and then fully discharge during the ―OFF‖ period (5-to-10RC) resulting in a perfectly matched RC waveform.

If the time period of the input waveform is made longer (lower frequency, ƒ < 1/10RC) for

example an ―ON‖ half -period pulse width equivalent to say ―8RC‖, the capacitor would then stay

fully charged longer and also stay fully discharged longer producing an RC waveform as shown.

If however we now reduced the total time period of the input waveform (higher frequency, ƒ

> 1/10RC), to say ―4RC‖, the capacitor would not have sufficient time to either fully charge duringthe ―ON‖ period or fully discharge during the ―OFF‖ period. Therefore the resultant voltage drop

across the capacitor, Vc would be less than its maximum input voltage producing an RC waveform as

shown below.


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CIRCUIT DIAGRAM:

PROCEDURE: Connect the circuit as shown in circuit diagram.

Select suitable values of R, C and compute f=1/10RC.

Select Square wave at frequency calculated in above step.

Calculate time constant using formula, RC

Celebrate CRO if required.

Connect the probe of CRO across capacitor to get wave form of capacitor voltages.

Note the value of VP and calculate 63.2% of VP

Calculate value of τ (τ Time/Div. * No. of Div. on X -axis when wave form is at 63.2%

of VP ) .

Compare the value of τ with the value calculated from formula of τ.


Sr. No. R C f Vp 63.2%VpRC) CRO)

1

2

3

PRECAUTIONS: While dealing with electric circuits handle the apparatus carefully. Make sure the connections are tight.



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Design and Implementation of RL Series Circuit for understanding of inductive transients and

time constant.

EQUIPMENT REQUIRED: Inductors

Decade Resistor Box

Cathode Ray Oscilloscope

Function Generator

Connecting Leads

THEORETICAL BACKGROUND:As we saw in previous lab, when a circuit containing capacitance is disturbed, voltages and

currents do not change to their new values immediately, but instead pass through a transitional phase

as the circuit capacitance charges or discharges. The voltages and currents during this transitional

interval are called transients . In a dual fashion, transients occur when circuits containing

inductances are disturbed. In this case, however, transients occur because current in inductance

cannot change instantaneously.

To get at the idea, consider Figure shown below, we see a purely resistive circuit. At the instant

the switch is closed, current jumps from 0 to E/R as required by Ohm’s law. Thus, no transient (i.e.,

transitional phase) occurs because current reaches its final value immediately. Now consider second

circuit. Here, we have added inductance. At the instant the switch is closed, a counter emf appears

across the inductance. This voltage attempts to stop the current from changing and consequently

slows its rise. Current thus does not jump to E/R immediately as in (a), but instead climbs graduallyand smoothly as in (b). The larger the inductance, the longer the transition takes.


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Inductor Voltage

Now consider inductor voltage. When the switch is open as in Figure (a) shown below, the

current in the circuit and voltage across L are both zero. Now close the switch. Immediately after the

switch is closed, the current is still zero, (since it cannot change instantaneously). Since v R = Ri, the

voltage across R is also zero and thus the full source voltage appears across L as shown in (b). Theinductor voltage therefore jumps from 0 V just before the switch is closed to E volts just after. It then

decays to zero, since; the voltage across inductance is zero for steady state dc. This is indicated in

(c).

Note that just after the switch is closed, the inductor has voltage across it but no current through

it. It therefore momentarily looks like an open circuit. This observation is true in general, that is, an

inductor with zero initial current looks like an open circuit at the instant of switching .

To study the response of an RL series circuit, consider an inductor (i.e., a coil with an inductance

L) in series with a battery of emf E and a resistor of resistance R. This is known as an RL circuit.

There are some similarities between the RL circuit and the RC circuit, and some important

differences.An RL Circuit with a Battery: First consider what happens

with the resistor and the battery. When the switch is closed we

have a current; when the switch is opened again we have no

current. Now add an inductor to the circuit. When we close the

switch now the current tries to jump up to the same value we

had with the resistor but the inductor opposes this because a

change in current means a change in flux for the coil. If the

inductor adds negligible resistance to the circuit the current

eventually reaches the same value it had with the resistor but

the current follows an exponential curve to get there.

Where =L/R

Waveforms for square wave input:


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VL

Time

The Time Constant

The rate, at which an inductor current achieves its final value, depends on the ratio of L and R

and it’s known as the time constant of the circuit and is given the symbol (the Greek letter tau).L/R has units of seconds.

Thus,

=L/R (seconds, s)

Duration of a Transient

The length of time that a transient lasts depends on the exponential function . As t

increases,

decreases, and when it reaches zero, the transient is gone. Theoretically, this takes

infinite time. In practice, however, over 99% of the transition takes place during the first five time

constants (i.e., transients are within 1% of their final value at t=5

). This can be verified by direct

substitution. Similarly, the current falls to within 1% of its final value in five time constants. Thus,

for all practical purposes, transients can be considered to last for only five time constants .

Moreover larger the time constant, the longer will be the duration of the transient.

CIRCUIT DIAGRAM:


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PROCEDURE: Connect the circuit as shown in circuit diagram.

Select suitable values of R, L and compute f=1/10RC.

Select Square wave at frequency calculated in above step.

Calculate time constant using formula, L R Celebrate CRO if required.

Connect the probe of CRO across capacitor to get wave form of capacitor voltages.

Note the value of VP and calculate 63.2% of VP

Calculate value of τ (τ Time/Div. * No. of Div. on X -axis when wave form is at 63.2%

of VP ) .

Compare the value of τ with the value calculated from formula of τ.


Sr. No. R L f Vp 63.2%VpL/R) CRO)

1

2

3




LEARNING AND FINDINGS: ________________________________________________________________

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Design and Implementation of RC Series Circuit using OrCad Capture PSpice circuit

simulation software to measure transient response & time constant.

SOFTWARE REQUIRED: OrCad PSpice

THEORETICAL BACKGROUNG:

OrCAD EE PSpice is a SPICE circuit simulator application for simulation and verification of

analog and mixed-signal circuits. PSpice is an acronym for Personal Simulation Program with

Integrated Circuit Emphasis.

We can analyze a circuit’s behavior using PSpice Simulation tool in many ways and confirm

that it performs as specified. A circuit to be analyzed using PSpice is described by a circuitdescription file, which is processed by PSpice and executed as a simulation. PSpice creates an output

file to store the simulation results, and such results are also graphically displayed within the OrCAD

EE interface.

The type of simulation performed by PSpice depends on the source specifications and control

statements. PSpice supports the following types of analyses:

DC Analysis - for circuits with time – invariant sources (e.g. steady-state DC sources). It

calculates all nodal voltages and branch currents over a range of values. Supported types

include linear sweep, Logarithmic sweep, and Sweep over List of values.

Transient Analysis

- for circuits with time variant sources (e.g., sinusoidal sources/switched

DC sources). It calculates all nodes voltages and branch currents over a time interval and

their instantaneous values are the outputs.

AC Analysis - for small signal analysis of circuits with sources of varying frequencies. It

calculates the magnitudes and phase angles of all nodal voltages and branch currents over a

range of frequencies.

RC Circuit:A resistor – capacitor circuit (RC circuit), or RC

filter or RC network, is an electric circuit composed

of resistors and capacitors driven by a voltage or current source.

A first order RC circuit is composed of one resistor and onecapacitor and is the simplest type of RC circuit.


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Basic user interface of PSpice:

Creating a new project in PSpice:

To begin, run the OrCad Capture program and create a new project by selecting File

| New | Project.

Choose an appropriate file name and a directory to store all of your files. Then create a

project using the Analog or Mixed-Signal Circuit Wizard. Click OK .

On the next screen you have to choose which PSpice part symbol library to load.

Placing Components:

Choose the circuit components by selecting Place | Part or the second button on the

vertical toolbar.

In the Place Part dialog window choose the circuit component from the appropriate

library. Following table lists the circuit components that you will use regularly, their

part name, and the libraries where they can be found.

Circuit Element Part Name Library

Independent DC Current Source IDC SOURCE

Independent AC Current Source IAC SOURCE

Independent DC Voltage Source VDC SOURCE

Independent AC Voltage Source VAC SOURCE

Resistor R ANALOG

Variable Resistor R_var ANALOG

Capacitor C ANALOG

Inductor L ANALOG


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Voltage Controlled Voltage Source E ANALOG

Current Controlled Voltage Source H ANALOG

Voltage Controlled Current Source G ANALOG

Current Controlled Current Source F ANALOG

PROCEDURE:• Choose the part named VDC for the independent DC voltage source, R for the resistors

and C for capacitor.

• Add the resistor and capacitor to your circuit by going to the ANALOG library and

highlighting the part name R and C and then click OK .

• In the Capture window your cursor will now turn into a diagram of the resistor.

• To change the orientation of any circuit component before adding it to the grid, press

CTRL-R , or right click and select Rotate.• To specify the attribute of the circuit component, you must add it in the attribute box.

• Note: Most circuit components will already have a default value. The default value for

the resistor is 1k Ω and the default value for the independent DC voltage source is 0V

DC.

• Double click on the attribute box, or right click on the attribute box and select Edit

Properties.

• In the Display Properties dialog window enter the desired value. This value can be an

integer or a real number.

Once all the circuit components are selected, you must connect them with wires.

• To create wires select Place | Wire, or click the third vertical toolbar button.

• Place a wire in your circuit by clicking on the starting node for the wire, and clicking

again at the ending node for the wire.

• Note: Make sure that the wires you place do not overlap any circuit components;

• To end the wire hit ESC, or right click on the mouse and select End Wire.

• To complete your circuit in PSpice you must add a circuit ground. On the vertical

toolbar select the GND button or select Place | Ground, and then choose the part

named 0/Source. Place the ground at an appropriate node in your circuit.

CIRCUIT DIAGRAM:


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Add probes and run the simulation:

There are two choices for voltage probes. The first is a single probe that ―measures‖ the voltage at

the selected node with respect to ground. The second is a pair of probes that measure the voltage

difference between them – just like the leads of a voltmeter. If measuring current, the current probe

must be attached the pin of a component, and it will measure the current flowing out of the

component at that pin.

• Click on the single voltage probe icon at the top of the window – an icon that looks a bit like

a turkey baster will be attached to the cursor.

• Click on the wire somewhere between the source and the resistor to attach the probe, which

will measure the source voltage with respect to ground.

• Then add another probe to measure the capacitor voltage. For variety, try using the double-

probe as shown below.

Setting up simulation Profile:

• Once you constructed the circuit

create a new simulation by

selecting PSpice | New

Simulation Profile. Choose an

appropriate name for the

simulation.

• In the Simulation Settings

dialog window, under the

Analysis tab select Time

Domain (Transient) as theAnalysis Type.

• In the General Settings option,

specify start time of the

simulation in the Start saving data after dialog box. This should usually be set to 0.

• Specify the end time of the simulation in the Run to time dialog box. This should

usually be set to about 5τ to 6τ, where τ is the time constant of your circuit calculated

by multiplying value of Resistor and capacitor.

Analyzing the simulation:

To analyze the graph and read values from the graph you need to use the cursors. Select Trace | Cursor | Display in the PSpice A/D window menu. The cursors should

now be displayed on the graph.

There are two cursors you can use; one cursor can be accessed by left clicking on the

graph with the mouse. Hold down the left click to move the cursor around on the graph.

The value that this cursor is pointing to, is displayed in the first entry of the Probe

Cursor dialog window (x-coordinate first, y-coordinate second).

The cursor that can be accessed by left clicking the mouse will always be displayed as

the first entry in this window.

When there is more than one waveform on the graph you can move the cursor onto

another waveform by clicking on the legend symbol (right click/left click depending on

which cursor you want to move) for the desired waveform located on the bottom of thegraph. i.e. the little square, triangle etc.


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It is recommended that you explore the Add Trace dialog window; there are many

other waveforms that you can choose from. You can even show the waveforms of the

currents in your circuit.

Settings for a transient simulation

One way of finding the time-constant from a graph like this is to extrapolate the initial decay linearly

and find the point at which it cuts the time axis. This should give the time-constant directly. Check itfor the plot. The output is more interesting from a pulse rather than a single step. Spice offers the

VPULSE source, whose parameters are listed in table 1 on the next page. Change the source in your

circuit to give a 0.2 ms pulse and plot both the input and output. You should find that the output

voltage goes negative for a while, although the input is always positive or zero. How is this possible?

GRAPH:Output voltage from the RC high-pass filter with time-constant τ = 1ms.


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Circuit Diagram:(Make Circuit diagram as instructed in assignment and paste here its print out.)

GRAPHS:

a) Square wave inputa) VC vs. time

b) VR vs. time

c) IC vs. time

d) IC vs. time


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OBSERVATIONS & CALCULATIONS:(Verify the results for time constant from your circuit diagram and from graph.)

LEARNINGS & FINDINGS:


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Design and Implementation of RL Series Circuit using OrCad Capture PSpice circuit

simulation software to measure transient response & time constant using pulsed voltage.

SOFTWARE REQUIRED: OrCad Pspice

THEORETICAL BACKGROUNG:

A resistor – inductor circuit (RL circuit), or RL filter or RL network, is an electric circuit composed of

resistors and inductors driven by a voltage or current source. A first order RL circuit is composed of

one resistor and one inductor and is the simplest type of RL circuit.

A first order RL circuit is one of the simplest analogue infinite impulse response electronic filters. It

consists of a resistor and an inductor, either in series driven by a voltage source or in parallel driven by a current source. Both RC and RL circuits form a single-pole filter. Depending on whether the

reactive element (C or L) is in series with the load, or parallel with the load will dictate whether the

filter is low-pass or high-pass.

Frequently RL circuits are used for DC power supplies to RF amplifiers, where the inductor is used

to pass DC bias current and block the RF getting back into the power supply.

The most straightforward way to derive the time domain behaviour is to use the Laplace

transforms of the expressions for and given above. This effectively transforms .

Assuming a step input (i.e., before and then afterwards):

Inductor voltage step-response. Resistor voltage step-response.

Partial fractions expansions and the inverse Laplace transform yield:

https://en.wikipedia.org/wiki/File:Series_RC_capacitor_voltage.svghttps://en.wikipedia.org/wiki/File:Series_RC_resistor_voltage.svg


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Thus, the voltage across the inductor tends towards 0 as time passes, while the voltage across

the resistor tends towards V, as shown in the figures. This is in keeping with the intuitive point that

the inductor will only have a voltage across as long as the current in the circuit is changing — as the

circuit reaches its steady-state, there is no further current change and ultimately no inductor voltage.

PROCEDURE:1. In setting up the simulation profile, we will choose a

―Transient‖ analysis, in which a time span is specified. The

voltages and currents in the circuit will be calculated at time

intervals, starting at t = 0 and extending through the specified

time span. At each step, new values are calculated, using the

values from the previous step as initial conditions. The step

size is determined by the program, although you can specify a

maximum step size.

2. We need to use sources that varies in time. The two most

common are VPULSE (or IPULSE) which is a square wave

and VSIN (or ISIN) which is a sinusoid. In order to specify

the shape of the waveforms, extra parameters are needed.

For the RC circuits in this tutorial, we will use the VPULSE

and IPULSE sources. Sinusoidal sources will be used in a

subsequent tutorial.3. We will need to use ―probes‖ to specify the voltages or

currents that will show as traces on the plot.

4. The plot will show up in a separate window, which has some analysis tools that might be

handy in certain situations.

5. From the source library, choose the ―VPULSE‖ source, as shown in figure, and place it in the

drawing window.

From the analog library, add a resistor and a

capacitor to the drawing window. Add a ground a

connection, and then wire the parts together, as

shown in figure.Change the inductor value to 1 2H (2H in PSPICE

terminology). The resistor can stay at 1 k Ω.)

The source has a number of parameters. A value

must be entered for each – if any are left blank,

PSPICE will complain and refuse to run the

simulation.


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V1 - Initial voltage voltage level

V2 - Voltage after the switch (note that V2 can be less than V1).

TD - Delay time before the first transition from V1 to V2.

TR - Rise time in going from V1 to V2. (It is still TR, even if the V1 < V2.) TF -

Fall time in going from V2 to V1.

PW - Pulse width – time that the voltage is at the V1 level.

PER - Period - the time for one cycle of the pulse wave form. The source will repeat the pulse for as

long as the simulation runs, as defined in the simulation set up.

Note: The value of PW be chosen according to 5T of the circuit and to make a ―square wave‖ with

abrupt transitions, set TR and TF to be very small – but not 0.

Set the parameters for the pulse to the values shown in the figure above. This should give

two clear transients from the circuit – one up and one down. The ―high‖ time, PW, is eight time

constants long. The ―low‖ time (PER – PW, assuming that the rise and fall are negligible) is also

eight time constants.

Set up the Simulation profile

Set up a new simulation profile. (Give it

whatever name you like.) From the pop-

up menu, choose the ―Time Domain

(Transient)‖ analysis type.

Add probes and run the simulation:

There are two choices for voltage probes.

The first is a single probe that

―measures‖ the voltage at the selectednode with respect to ground. The second

is a pair of probes that measure the

voltage difference between them – just

like the leads of a voltmeter. If measuring

current, the current probe must be

attached the pin of a component, and it will measure the current flowing out of the component at that

pin.

The plot

If the simulation runs successfully, a plot window will open. Initially, it may be hidden behind the

drawing window – click the flashing icon in the tray at the bottom to bring the plot to the front. The

t = 0

TD

PW

PER

TR TF

V1

V2


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plot should have traces of the two probe voltages. The plot traces will now be color coded to the

probes.

Analyzing the simulation:

To analyze the graph and read values from the graph you need to use the cursors.

Select Trace | Cursor | Display in the PSpice A/D window menu. The cursors

should now be displayed on the graph.

There are two cursors you can use; one cursor can be accessed by left clicking on

the graph with the mouse. Hold down the left click to move the cursor around on

the graph.

The value that this cursor is pointing to, is displayed in the first entry of the Probe

Cursor dialog window (x-coordinate first, y-coordinate second).

The cursor that can be accessed by left clicking the mouse will always be displayed

as the first entry in this window.

It is recommended that you explore the Add Trace dialog window; there are many

other waveforms that you can choose from. You can even show the waveforms of

the currents in your circuit.

GRAPH:


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Circuit Diagram:(Make Circuit diagram as instructed in assignment and paste here its print out.)

GRAPHS:

b) Square wave inpute) VC vs. time

f) VR vs. time

g) IC vs. time

h) IC vs. time


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OBSERVATIONS & CALCULATIONS:(Verify the results for time constant from your circuit diagram and from graph.)

LEARNINGS & FINDINGS:

Documents

ENA Lab Manual 2k14 Spring-2016 First 7 Labs