ECCE4466_Power Electronics Lab

8/4/2019 ECCE4466_Power Electronics Lab

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Power Electronics Lab Manual

SQU-ECE2004 Page 1 of 20

Sultan Qaboos University

College of EngineeringDepartment of Electrical and Computer Engineering

ECCE4466: Power Electronics

Student Lab Manual

Prepared by: Date

Dr. Adel Gastli Fall 2004Mr. Mohammed Al-Badi Fall 2004

Updated by: Date


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INTRODUCTION TO THE TRAINER

The component module consists of:

- Four thyristors

- Three diodes

- One power transistor- One triac

All components, except the transistor is protected by 10 A fuses and RC connection against

transient over voltages. The transistor is protected by a 1.6 A fuse.

The trigger module consists of:

- One universal trigger circuit for mains commutated applications.

- One trigger circuit for self commutated applications.

- One DIAC trigger circuit.

- One mains rectifier.

- Transformer, inductor and capacitors.

1

1

_

+

T

+

+

testslow

K2

G2

K1

G1

G1

K

G++ C2C1

L

K2

G2

K1

df

mains

control

sync

BASIC POWER ELECTRONICSTRAINER MV 4208TERCO


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Lab Manual Contents

Experiment PE.1 ..................................................................................................................... 4

Experiment PE.2 .................................................................................................................... 8

Experiment PE.3 ...................................................................................................................10

Pre-Lab: Experiment PE.4...................................................................................................12

Experiment PE.4 ...................................................................................................................13

Experiment PE.5 ...................................................................................................................15

Experiment PE.6 ...................................................................................................................17

Appendix A: How to get a good grade in the lab report?..........................................20


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Experiment PE.1

Diode

1. Aim of the experiment

The aim of this experiment is:

1. To study the basic properties of the diode.2. To study and plot the conducting characteristics of the diode.3. To study the diode operation as a half-wave rectifier.

2. Equipment and Components

1 Basic power electronic trainer model MV 4208

1 Variable resistor 100 , 3A1 Variable resistor 50 W, 500 MV 1962

1 D.C. power Supply PL 310

2 Multimeters

3. Conducting the experiment

Part 1 Reverse-biased (blocked) diode operation

1. Connect the circuit as shown in Fig. 1.2. Increase the voltage from 0 to 200V.3. Read the current I on the meter.

V(V) 50 100 150 200

I(A)

4. Why is it called reverse operationPlot the I-V Characteristic of the diode in the reverseregion?

5. Comment on the results.Part 2 Conduction (forward-biased) diode characteristics

1. Connect the circuit as shown in Fig. 2.2. Set the current limit of the power supply to maximum.3. Increase the voltage to 1.5V.4. Turn the resistance to 0 position.5. Switch on the power supply.6. Very carefully turn the resistance knob until all the current readings on the table are read

off.


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Vd(V)

Id(A) 0.01 0.02 0.04 0.06 0.08 0.1 0.15 0.2

Vd(V)

Id(A) 0.25 0.3 0.35 0.4 0.45 0.5 0.55

7. Plot the V-I characteristic of the diode from the above results.8. Deduce the value of threshold voltage for this diode.Part 3 Half-wave rectifier

1. Connect the circuit as shown in Fig. 3.2. Switch on the voltmeter (DC range)3. Switch on the Basic Power Electronic Trainer.4. Take the reading of the voltmeter (DC range).5. Two waveforms can be seen on the oscilloscope. Ch1 220V AC and Ch2 rectified DC

half wave.

6. Sketch the rectified voltage waveform.7. Turn off the mains supply.8. Calculate the average DC output voltage from your sketch.


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Fig.1: Reverse operation circuit

100

I

V

V1.5 V DC

0

I

V

-+

MV 1962_

+mains

(a) Actual circuit connections

(b) Equivalent circuit diagram


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Fig.2: Conducting operation circuit

Fig.3: Half-wave rectifier circuit

I

V

V 1.5 V

VVV A_

+

0 100

I PL 310

V




220V ~

V

220V ~

V

_

+mains

0 100

MV 1962

Scope

Ch1 Ch2


110V ~

110V ~


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Experiment PE.2

Thyristor

1. 1. Aim of the experiment


1. To study the basic properties of the Thyristor.2. To study and plot the conducting characteristics of the thyristor.



1 Variable resistor 500 W, 500, MV 1962

1 Variable resistor 10 , 3.2 A1 D.C. power Supply PL 310

3 Multimeters


Part 1 Thyristor properties

1. Connect the circuit as shown in Fig. 1.2. Ensure that both resistors are set to max. resistance (i.e. 0)3. Switch on all meters and then the power supply.4. Set the current limit to maximum and increase the voltage supply to 10V.5. Increase VT to approx. 1.5 V using MV 1962.6. Increase VG using the 10 resistor until the thyristor fires (current flows).

Note this voltage VG = ..

6. Reduce VG to zero and check that the thyristor switches off.7. Increase VT to approx. 3 V using MV 1962.8. Repeat step 6 and compare this voltage with VG in step 6.9. Reduce VG to zero and check that the thyristor continues to conduct.10.Reduce VT gradually and keep checking on IT. When the thyristor switches off (blockes)

take readings of IT and VT

IT = .. VT =.

Q1: What does this current represent, and what does it called?

Q2: Why the thyristor switched off in 7?

11.switch off the power supply

Part 2 Conduction (forward-biased) thyristor characteristics

12.Turn on the power supply.13.Increase VT to approx. 3 V using MV 1962.14.Trigger the thyristor by increasing VG and then reduce VG back to minimum.15.Increase VT in steps until IT reaches 0.9 Amp. Fill in the following table


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IT(A) 0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

VT (V)

17. Plot the curve IT verses VT and comments on the graph.

Fig.1: A circuit for thyristor operation

VTv

VG

I

5 V DC

+

500

10

VVV A_ +

0 100

MV

0 100

IT

VT

V

PL 310

10 , 3.2 A




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SQU-ECE2004 Page 10 of20

Experiment PE.3

Transistor


The aim of this experiment is to plot and study voltage and current characteristics of a power

transistor.



1 Variable resistor 500 W, 500 , MV 1962

1 Variable resistor 10 , 3.2 A

1 D.C. power Supply PL 3103 Multimeters


1. Connect the circuit as shown in Fig. 1.2. Set the the 10 resistor to 50%3. Set the MV 1965 resistor to maximum resistance (i.e. 0%)4. Set the current limit to maximum and increase the voltage supply to 5V.5. Switch on the power supply and the multimeters.6. Using MV 1965, carefully adjust the collector current to read as near as possible those

values in the table. At each value read off IBE and VBE and record the values in the table.7. When you finish, switch off the power supply and the multimeters.

IC (mA) IB (mA) VBE @ VC=5V =IC / IB @ RC=5

25

40

60

80

100

200

400

600

8. Plot IB vs. IC, VBE vs. IC and vs. IC9. Comments on the figures.


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v

V

Ic

5 V DC

+

10

500



VVV A_ +

0 100

10 , 3.2

0 100

I

IB

V

MV 1965

B

EB

C

B

IB

Fig.1: A circuit for transistor operation


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Pre-Lab: Experiment PE.4

DC-DC Conversion

(Buck Chopper)

Design a buck converter to supply a resistive load [100] with a variable output DC voltage

[2V-8V] from a fixed DC supply [10V]:

Use an ideal switch. For the control signal, use a frequency of 200Hz. Simulated your design using Simulink and fill in the following table.

VDC input Duty Cycle (k) VDC output(V) (%) (V)

10 80

10 7010 60

10 50

10 40

10 30

10 20

Plot VDC output as function of the Duty Cycle k.

Submit this pre-lab report before you start your lab experiments PE.4.


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Experiment PE.4

DC-DC Conversion (Buck Chopper)



1. To use the BJT as a switch.2. To study a simple chopper circuit.



1 Resistor 100

1 D.C. power Supply PL 310

2 Multimeters


1. Using an oscilloscope, set the function generator so that it produces a rectangularwaveform with amplitude of 1.5 V and a frequency of 200 Hz.

2. Connect the circuit shown in Fig. 1. Connect the +ve terminal of the function generator tothe base of the BJT and the ve to the ground. Connect Ch1 to B, Ch2 to the C and the

ground of both channels to E.

3. Set the output of the DC power supply to 10V and the current limit knob to max.4. Using the function generator, vary the duty cycle of the controlling signal and fill in the

following table.

Time setting: ..ms /div

Duty cycle

K (%)

T

(div)

ton

(div)

Measured

VDC output (V)

Calculated

VDC output (V)

80

70

60

50

40

30

20

Plot the measured and calculated DC output voltages versus duty cycle (k). Comments on

the graph.

5. What could be the reason(s) behind the difference between the measured and thecalculated values?


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Fig.1: Basic Chopper Circuit

Load:100

VDC 10V+

Function

Generator

-

C

B

E

Scope

Ch1 Ch2

V

+

-

A


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Experiment PE.5

Half Controlled AC-DC Bridge


The object of this experiment is to:

- Examine and understand the principle of single phase half controlled rectifier bridges.

- Study the output and triggering waveforms.


1 Basic Power Electronics Trainer MV 4208

1 Lamp Unit 100 W, 220V MV 1428

1 Two-channel oscilloscope

1 Probe1 Diffprobe MV 1971


1. Connect the circuit as shown in Fig. 1.2. Set the oscilloscope as follow:

- Ch.1. Volts/div. to 1 D.C.

- Ch.2. Volts/div. to 2 D.C.

- Mode switch dual

- Time/div. to 5 ms

- Trig. source Ch.1.- Trig. mode to Auto.

3. Set the synchronizing potentiometer and the load voltage potentiometer to max. leftposition.

4. Switch on the basic trainer.5. The output voltage and trigger pulses are seen on the oscilloscope. Sketch or photograph

the waveforms.

6. Turn slowly the load voltage potentiometer clockwise until the firing angle is 45.7. Sketch the waveform of the trigger pulses and the output voltage.8. Repeat stages 6 & 7 and fill the results in Table 1.

Table 1: Variation of average output voltage as a function of the triggering angle

o 0 45 90 135 180

Average output Voltage (V)

Calculated output voltage(V)

Question 1.

Compare the resulting waveforms and comment on the relationship between firing angle and

load voltage.

Question 2.

Plot the relation between the average output voltage in volts and firing angle .


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Use the firing angle of table 2 to plot the following equation: ( )

cos1+= moutputV

V

where Vm is the peak value of the input ac voltage.

Question 3.

Simulate the same circuit with Matlab/Simulink and compare the experimental plots and

waveforms from the simulated circuit.



Fig.1: A circuit for half-controlled rectifier

TRIGGER

CONTROL

CIRCUIT

SYNC.

220 V~

+_

DIFFPROBE

MV 1971

MV

TO

SYNC.

8

9

LOAD

SWITC

_

+

CH1 CH2LOADVOLATAGE

Scope


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Experiment PE.6

Single Phase AC Voltage Controller


The objective of this experiment is to introduce the rms. ac voltage regulation based on simple

back-to-back thyristors.


- Basic Power Electronics Trainer MV 4208

- Lamp Unit, MV 1418 (220 Volt, 100 Watts)

- Diffprobe MV 1971

- A 2-channel storage oscilloscope

- 2 Voltmeters


1. Connect the circuit as shown in Fig. 1.2. Set the oscilloscope as follow:

- Channel 1 to 5 V/div.- Channel 2 to 20 V/div.- time base to 5 msec/div.

3. Connect one voltmeter across the load and the other one across one thyristor.4. Turn the potentiometers marked 1 and 2 on Fig. 1 to maximum left (anticlockwise).5. Switch on the oscilloscope, the diffprobe and Basic Power Electronics Trainer. Remember

that should switch OFF the diffprobe whenever you are not using it.

6. Note that the triggering pulses on channel 1 are continuous, consequently the maximumpower is available on the load and the lamp should light to full brightness.

7. Study the two displays on the oscilloscopes when the pulses are continuous.Question 1.

What is the value of when the pulses are continuous? What is the value of the r.m.s.

voltage acrossa. the lamp (load): . b. the thyristors: .

8. Turn potentiometer 2 gradually clockwise until you notice a break between the firing pulses. Observe that during these break (off) periods there is no voltage to the load

(thyristors open) while the thyristors voltage is the supply voltage during their off period.

The light should dim slightly.

9. Continue to turn potentiometer 2 clockwise and record the value of r.m.s. voltage acrossthe load (VL) & thyristors (VT). The pulse burst reduces until there is no triggering and the

light extinguishes.

10.Fill-in the results in the following table.


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o 0 45 90 135 180

VL (rms)

VT(rms)

Question 2.At =45

o, sketch the waveform of the triggering pulses with the output voltage in one graph;

and the triggering pulses with the thyristor voltage on another graph. Comment on the

relationship between the three waveforms.

11.Switch OFF the oscilloscope, the diffprobe and Basic Power Electronics TrainerQuestion 3.

Plot VL & VT(in Y-axis) against o (in X-axis) and comment on resulting curves.


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a) Actual circuit connections


Fig.1: Single phase AC voltage controller circuit

Diffprobe

MV1971

MV1418

TO

SYN

_

+

CH1 CH2

Phase

SYNC

Oscillosc

1

2

TRIGGER

CONTROL

CIRCUIT

SYN

C.


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SQU-ECE2004 Page 20 of

Appendix A: How to get a good grade in the lab report?

Your report should include the following sections:

1. Objectives2. Theoretical background/Introduction3. Experimental Results: This section includes all experimental results, graphs, and

answers to all questions including commenting on graphs or numerical results.

4. Conclusions: a summary of what you have accomplished in the lab.5. References: a list of any book, magazine, or website you have used in your report; at

least one reference e.g. text book, lab manual, internet site,

All tables and figures should be labeled with captions. e.g. Table 1: Diode characteristics

or Fig.1: Diode characteristics. The captions for tables should be centered on top of tables

and the caption for figures should be centered on the bottom of the figures.

5 points are allocated for the cover page Also. The cover page should include:

The names of the University, College, and department. The course title and code The title of the experiment Names of the group members and their Ids Name of the instructor to whom the report is submitted

The last 10 points is allocated for the format and the layout of the report. This includes but

not limited to:

Page numbers

No hand writing i.e. all parts should be written using a word-processing program. Numbering of the sections e.g. Part 2 in Experimental Results should be:

2.2 Part II The total report mark is 100. Any penalty points (related to attendance and late report

submission) will be reduced from this mark.

Whenever you present experimental data graphically (using curves), show the points at

which you took your reading on the curve. Do not forget: Axis label, Units, Legend (when

applicable) and the Title. Also, to make the curve more clear and to save ink, delete the

plot area (the background of the curve).

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