Assignement 2 -- Experiment 8

7/31/2019 Assignement 2 -- Experiment 8

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Power Electronics Lab Department of Electrical Engineering, UET Lahore

Lab Instructor: Syed Abdul Rahman Kashif 4

To place the ground on the circuit Go to Place => Ground and choose 0/source (If you don't see the

"source" in the Libraries section, you will need to add the source library. See Part Notes below).

3. Mega- (i.e. mega-ohm, mega-hertz)

When you need to enter a "Mega-" (106) unit use "MEG". (Case doesn't matter). "M" is NOT mega,

it is milli (10^-3). Example: for 6.5 megahertz, enter "6.5 Meg", for 3 milli-amps, enter "3 m"

4. All parts must have unique names.You can't have two parts named "R1" in your circuit. If you are copying and pasting parts or circuits,

you will need to rename your parts because PSpice doesn't do this automatically.

5. Labeling Nodes:

I recommend you use aliases to label your input and output nodes. This makes your node easier to

find. V(Vout) is simpler than finding V(R1:1)

a. Go to Place => Net Aliasb. Enter a name, i.e., Vout or Vinc. Place the label close to a noded. Example below shows a simple circuit with aliases:


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Simulation Notes

1) DC Bias:

The response of the circuit to DC sources is always calculated. To display DC bias voltages and

currents on your circuit after you run the simulation, go to PSpice => Bias Points, and check Enable,

Enable Bias Current Display, and/or Enable Bias Voltage Display

2) Parametric Sweep

This simulation is used to find the response of the circuit (e.g., current in one element) if the value of

an element (R1 in the example below) is changed. To do so:

a. Change the value of the part to {RL} (use curly braces, name is arbitrary)b. Go to Place => Partc. Add a PARAM/SPECIAL part to your schematicd. Double click on the PARAM parte. Click New Columnf. Set the name to RL (same name as in a but with no curly braces)g. Set the value to something, e.g., 1k (this is the value that is used in calculating DC bias

values, choose somewhere in the range of your sweep).

h. Click "Display"i. Select "Name and Value" and press OK

j. Your schematic should look like as in figure below

k. Go to PSpice=>Edit Simulation Profile.l. Change the following settings, Analysis type: DC Sweep ,Options: Primary Sweep, Sweep

variable: Global parameter, Parameter name: RL, Setup the sweep type how you want. (Note

that if you are sweeping resistance, you can't start at 0)


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m. Click OK, and go to PSpice => Run to run the simulation.3) Frequency Domain Simulations

1. Set up your circuit with VAC voltage sources.2. Go to PSpice => Edit Simulation Profile3. Select the "Frequency Domain" Analysis type4. Select the frequency range of interest. Don't start Frequency sweeps at 0!5. Set the points/Decade to be at least 20.

Bode Plots

1. Use a logarithmic x-axis for the frequency.2. The magnitude should be measured in decibels. Use the PSpice DB() function to convert to

decibels. For example, DB(V(Vout)/V(Vin)), assuming you have labeled your output andinput nodes with "Vout" and "Vin" aliases. Note that DB(Vout) is NOT the transfer function

in dB.

3. Remember you also need a phase graph (unless instructed otherwise). Use the PSpice P()function to get the phase angle. For example, P(V(Vout)/V(Vin))

4. Be sure to mark the cutoff points on your bode plots (on both magnitude AND phase graphs).Remember cutoff is 3dB below the highest point (NOT always at -3dB)

a. Click the "Toggle Cursor" button. (Or go through the menu, Trace => Cursor =>Display) You will now be able to move the cursor along your plot.

b. Click the "Cursor Max" button to find the highest point. (Or go through themenu, Trace => Cursor => Max)

c. Click the "Mark Label" button to label that point. (Or go through the menu, Plot=> Label => Mark)

d. Click the "Cursor Search" button (Or go through the menu, Trace => Cursor=>Search Commands)

e. Select 1 for Cursor To Move to search along the y-axisf. Enter "search forward level (max-3)" (don't enter the quotation marks) to move the

cursor to the right to the point which is 3 below the max.


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g. Or enter "search back level (max-3)" (don't enter the quotation marks) to move thecursor to the left

h. Click the "Mark Label" button to label that cutoff point.a. Unclick the Toggle Cursor button to disable the cursor so you can move the label.b. Double click on the label to edit the text (to add units, or to name the point)

5. It may help to increase the width of the lines in the plot. The colored symbol at the bottom of the graph, or on the graph line Note you can select all of the lines by going to Edit => Select All Right click on the line. Make sure the selection list has Information, Properties,

Cursor 1, and Cursor 2.(If it lists Settings and Properties, you clicked on the

background, not on the line).

Select Properties You can change the width and other settings of that trace

4) Time Domain Simulations

a. Use VSIN for your voltage source instead of VAC (VOFF is the DC offset, VAMPL is theamplitude, and FREQ is the frequency of the sine wave).

b. For Square and triangular wave, use VPULSE


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Square Wave is the VPLUSE function in the limit of TR = TF = 0 and PW = 0.5 * PER (PER is the

period of the wave). This limit case, however, causes numerical difficulties in calculations. In any

case, we can never make such a square function in practice. In reality, square waves have very small

TR and TF. Typically, we use a symmetric function, i.e., we set TR = TF and PW = 0.5 * PER - 2 *

TR. Thus, for a given frequency we can set up the square function if we choose TR. If we choose TR

too large, the function does not look like a square wave. If we choose TR too small, the program will

take a long time to simulate the circuit and for TR smaller than a certain value, the simulation will

not converge numerically. A good choice for TR is to set it to be 1% of the PER (a period): TR = TF

= 0.01 * PER, PW = 0.48 * PER. This usually results in a nice signal without a huge amount of

computational need. Note that TR does not have to be exactly 1% of PER. You can choose nice

round numbers for TR, TF, and PW.

Triangular Wave is the VPLUSE function in the limit of TR = TF = 0.5* PER and PW = 0(convince yourself that this is the case). As before, the limit case of PW = 0 causes numerical

difficulties in calculations. So we have to choose PW to be a reasonably small value. A good choice

for PW is to be set at 1% of the PER (period): PW = 0.01* PER, TR = TF = 0.49 * PER (and not TR

= TF = 0.495 * PER so that we get a symmetric function). This usually results in a nice signal

without a huge amount of computational need. Again, note that PW does not have to be exactly 1%

of PER. You can choose nice round numbers for TR, TF, and PW.

Simulation settings

1. Go to PSpice => Edit Simulation Profile2. Select the "Time Domain (Transient)" Analysis type3. Enter a Run to time: so that a few periods will be displayed. Remember that the period

(seconds) = 1/frequency (Hz), i.e, if you are using a 1kHz sine wave, it has a 1/1kHz=1ms

period, so use a Run to time of 5ms for 5 periods

4. Set the Maximum step size to be much smaller than the period i.e. for a 1kHz sine wave: Ithas a 1ms period, so set a maximum step size of approx .01ms. (This works out to 100 data

points per period).

5. If you don't set the maximum step size, PSpice may choose one which is too big, makingyour sine wave look angular and ugly.


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Experiment

Single Phase Full Converter

Instructions:

All Practice and Exercise Questions must be completed in this lab session for full credit. You must show the outputs to the instructor before proceeding to the next question. Read this lab manual completely at least once before coming to lab.

Recommended Reading:

Power Electronics Circuits Devices and Applications by Muhammad H. Rashid 3rdedition.

Objectives:

The purpose of this experiment is to simulate Single Phase Full Converter.Tools required:

Software simulator ORCAD Calculator

LAB ACTIVITY:

1. Run the simulation software Orcad on your computer.2. Go to file and select new project.3. Name the project with your roll no. like 20XXEXXX and also specify the directory to save

project. Choose Analog or Mixed A/D. Click ok.


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4. In the next window Check create a blank project and click ok.

5. In the schematic window make the following circuit.6. Go to place, select part and add all the PSPICE libraries. Then select the following parts and

place on the schematic page.

Resistor Inductor Vsine Vpulse Thyristor S2800N

7. Go to place, select part and place PARAM in the schematic to specify parameters.8. Double click on PARAMETER after placing it and add variables to it one by one by clicking

on add new column button at the top of spread sheet. Specify the name and value of each

parameter. Use bracket {} as shown in schematic to specify values.


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9. After placing the components and specifying parameters make the simulation profile. Go toPSICE and select New Simulation Profile. A new window will appear.

10.Set the values as shown in figure below and click ok.

11.Run the simulation by pressing the play button.


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12.A new window will appear, go to ADD TRACE and plot the required waveforms.

13.Nominal values are: Vs = 220 V L = 20 mH R = 100 ohms f = 50 HzPARAMETERS:

TD1 = {((0/360)*T)+((angle/360)*T)}

TD2 = {((0/360)*T)+((angle/360)*T)}

TD3 = {((180/360)*T)+((angle/360)*T)}

TD4 = {((180/360)*T)+((angle/360)*T)}

PARAMETERS:

f = 50T = {1/f }

Vac = 220angle = 30PW = 350uRload = 100Lload = 100m


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Practice No.1

Set the value of angle=30 and run the simulation and compare your results with figures given

below.

Figure 1: Output Voltage.

Figure 2: Output Current.

Figure 3: Input Current.


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Figure 4: Input Voltage.

Figure 5: FFT of Output Voltage.

Comments about waveforms:

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Exercise No.1

Set the value of angle 60, 90 and plot output current and voltage waveforms. Also plot input

supply current and FFT of output Voltage.

1) Firing Angle = 60 degree

Plot Output Voltage

Plot current through load

Plot Voltage across the thyristor


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Plot input current

Plot FFT of output voltage

2) Set the firing angle equal to 90 degree

Plot output voltage


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Plot Output Current

Plot Input Current

Plot voltage across thyristor


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Plot FFT of output voltage

Exercise No.2

Repeat Exercise No.1 with resistive load R=10

1) Set the firing angle equal to 60 degreePlot the Output Voltage

Plot the load current


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Plot the input/supply current

Plot the FFT of Output Voltage

2) Set the firing angle equal to 90 degreePlot output voltage


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Plot the supply current

Plot the FFT of Output Voltage


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Exercise No.3

Repeat Exercise No.1 with inductive load L=20mH.

1) Set the firing angle equal to 60 degreePlot the output voltage




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Plot the FFT of output voltage

2) Set the firing angle equal to 90 degreePlot the load voltage



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Plot the load voltage spectrum

Exercise No.4

Observe and plot the FFT of the input and output voltage and current waveforms from

fundamental frequency to 1000 Hz. Use R=100 and L=20mH.

Plot load voltage spectrum


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Plot load current spectrum

Plot supply current spectrum

FFT of Intput Voltage

Documents

Assignement 2 -- Experiment 8