Final Epm15th April

7/28/2019 Final Epm15th April

1/14

Coursework Submission and Feedback Form CSFF-3Name sanyam Names of Group Members(if applicable)

Student No. Intake: PT1084421

Module Code & Title CE00132-2 Electrical Power &Machines

Assignment Title Power Electronics kit [(1) SCR characteristics & (2)Chopper circuits].

Name of Lecturer Karan Aneja

Date Due 15th

April 2013 Student E-Mail:pt1084421

I have read and understand the regulations on Plagiarism and Academic Dishonesty and declare that the work submitted does

not breach those regulations. Signed: ______________________________

You must now hand in to the designated APIIT Administrator - ensure that you receive your receipt

Received By Signature Date Time

Criteria Weighting FailMarginal

FailPass Credit Distinction

Not

Applicable

1 Object, Circuit diagrams,

Procedure

10 %

2. Introduction, Theory,

Apparatus

20%

3. Tables, Graphs,

Calculations

50%

4. Precautions, Results,

Conclusion,

20%

5.TOTAL 100%

Additional Comments: (These may be listed below or attached)

Provisional Assessment Result: Grade Date Lecturer's Initials

Taking account of the above factors, the overall provisional assessment of your work is:

Distinction Credit Pass Marginal Fail FailA+: 80% A: 75-79% B+: 70- 74% B: 65-69%, C: 55-64%, D: 50-54% F+: 40-49%, F: 0-40%

The comments and assessment result are subject to both internal and external moderation at the appropriate Examination Board. Consequently,they may not reflect your final grade. You may not appeal against these results on grounds of Academic Judgement

APIIT


2/14

Faculty of Computing, Engineering and Technology

You must attach this sheet to the front of your report

Award Title: BEng(Hons)/MEng in Electrical Engineering; Mechatronics, Electronic

Engineering

Level: 2

Module Code: CE00132-2

Module Title: Electrical Power and Machines

Assignment Title: Power Electronics kit [(1) SCR characteristics & (2) Chopper circuits]

Assessor: Karan Aneja

Date Set: 30

th

March 2013 Date to be handed in: 15 April 2013

Registration Number:

(As shown on your Registration Card)


3/14

Technical Criteria

Marks Comments / Remarks

(1) SCR

characteristics

(2) Chopper

circuits

(a) Object, Circuit

diagrams,

Procedure

/5 /5

(b) Introduction,

Apparatus & Theory /10 /10

(c) Tables, Graphs,

Calculations /25 /25

(d) Results,

Precautions,

Conclusion.

/10 /10

TOTAL MARKS

/50 /50

OVERALL MARKS

/100


4/14

SCR Characteristics (forward/reverse)

Aim:-To Study the static characteristics of a SCR.

Apparatus Required:- SCR Characteristics study unit, connecting wires.

Introduction:- Silicon is used for its construction and its operation as a rectifier (very low resistance in

the forward conduction and very high resistance in the reverse direction) can be controlled. Like the

diode, a SCR is a unidirectional device that blocks the current flow from cathode to anode. Unlike the

diode, a SCR also blocks the current flow from anode to cathode until it is triggered into conduction by a

proper gate signal between gate and cathode terminals.

THEORY: The silicon controlled rectifier (SCR) is a semiconductor device which acts as an electronic

switch. SCR is the most popular member of the thyristor family. It is a four layer three junction PNPN

device having three terminals and is used as a controlled switch. It converts AC to DC and also controls

the amount of power fed to the load. SCR has two states, i.e. either it does not conduct or it conducts

heavily. There is no state in between. SCR behaves like a switch. There are two ways to turn on the SCR,

the first method is to keep the gate open and make the supply voltage equal to the break over voltage. The

second method is to operate SCR with supply voltage less than break over voltage than turn it on by

means of a small current applied to the gate.

Circuit diagram SCR


5/14

SCR forward characteristics:-When SCR anode is connected to positive through an external

resistance, Junction J1 (P1 N1) and junction J3 (P2 N2) are forward biased. But junction J2 is reverse

biased. Hence the total voltage applied to the device appears across reverse biased junction J2. The block

over capability of this junction is the maximum forward blocking voltage with gate open. When a small

gate current is applied between gate and cathode (i.e. junction J3 (P2 N2), the junction tries to conductresulting in reducing the depletion layer on P2 side.

Hence the forward break over voltage decreases. If the gate current is increased, the forward break over

voltage further decreases. When SCR is fired gate loses its control, the current in the circuit is maintained

by the external load resistance. As already mentioned, the scr is a four-layer device with three terminals,

namely, the anode, the cathode and the gate. When the anode is made positive with respect to the

cathode,junctions J1 and J3 are forward biased and junction J2 is reverse-biased and only the leakage

current will flow through the device. The SCR is then said to be in the forward blocking state or in the

forward mode or off state.

Procedure:-

(a) with open gate:-

1. Connect the circuit diagram as given.

2. Switch on Kit observe whether meter are reading 0.

3. Set both voltages to minimum position, and then switch on SPDT.

4. Keep the supply control knob to minimum position.

5. Select mill ammeter range to 2mA and voltmeter range to 30V.

6. Increase anode supply voltage Vaa and note down corresponding anode-cathode

voltage and anode current Ia as Ia is small SCR is in off state.

7. Tabulate the readings in the table.


6/14

(b) when gate is positive:-

1. Connect the circuit as shown.

2. Repeat step (2) to (4) as given above.

3. Select milli ammeter range to 30mA.

4. Increase gate current (Ig) in small step at a particular value of Ig, SCR will turn ON

resulting sudden increase in anode current Ia.

5. Change the range of voltmeter to 2V after triggering of SCR record all possible

values of Ia and corresponding Vak.

6. Also note the gate current Ig required for triggering the SCR at a given Vak.

7. Record different break over voltage and triggering gate currents.

8. Record the possible results and plot the graph between anode to cathode voltage

and anode current.

SCR REVERSE CHARACTERISTICS:-

1. Connect the circuit same as scr forword characteristics.

2. Repeat all the steps as in case of forward characteristics procedure carefully.

3. Tabulate the readings in the table.

4. Record all the possible results and plot the graph between anode to cathode voltage

and anode current.

Circuit diagram for SCR reverse characteristics.


7/14

Tabl

e (a)

SCR

mea

sure

men

ts and calculations.

Precautions :-

1)The SCR should not be touched while passing the current through it as

the current large.2) SCR comes to ON state by appropriate gate current not by break over voltage.

3) SCR should be operated with a minimum value of gate current.

4)All the connections should be tight.

5)Never touch the live terminal during the experiment.

6)Before changing the connection, switch off the supply properly.

7)Always wear shoes when working in the lab. Avoid wearing loose clothes, hanging chains.

Disscussion and Conclusion:- When a P-N junction is added to junction transistor, the resulting

three junction device is called a silicon controlled rectifier. Thus, the structure of the silicon controlled

rectifier (SCR) consists of four alternate P- and N-type layers, as in the four layer diode.The SCR has

three

junctions J1, J2 and J3 and three terminals Anode (A), Cathode (C) and Gate (G). The function of the

gate is to control the firing of SCR. In the normal operating conditions of SCR, anode is held at high

positive potential with respect to cathode and gate at small positive potential with respect to cathode.

Junction areas of SCR are very large since they conduct large currents. In general the SCR works in two

cases 1) When the gate is open 2) when the gate is positive w.r.t. cathode. In both the cases anode is at

high positive potential. To understand how the SCR operates within a circuit, it is best to look at its

equivalent circuit. From this it can be seen that the SCR can be considered to consist of two

interconnected transistors.

Result:- 1. Graph between VAk and IAK representing the characterstics of the SCR is drawn.

2. weObserve that, by increasing the gate current the device can be triggerd earlier.

3. We successfully recoreded the anode to cathode voltage, anode current, triggering gate

Sl.no Gate Current Anode-cathode

voltage va

Anode current

Iag(ma)

1 0.05

2

3

4

5

6


8/14

current, holding current, holding voltage, break over voltage.

GRAPH:-


9/14

References

1.Electric Machinery, Fourth Edition, Fitzgerald, Kinglsey, and Umans,

McGraw-Hill Book Company, 1983, Chapter 1.

2. Electromagnetic and Electromechanical Machines, Matsch, Leander W., Intext

Educational Publishers, 1972.

3. Electromechanical Devices for Energy Conversion and Control Systems, Del

Toro, Vincent, Prentice-Hall, Inc., 1968.

4. http://seminarprojects.com/s/advantages-of-oc-test-and-sc-test-single-phase-transformer

5.Muhammad Mazidi & Janice Mazidi, January 2002, National Cheng Kung University Press, Hong

Kong.

6.Stan Gibilisco, G August 2005, Electrical Demystified, McGraw Hill Press, New York.


10/14

Chopper Circuits(step up & step down)

Aim:- To Study Step Up and Step Down Chopper.

Apparatus required:- Step Up and Step Down Chopper kit, Patch chords and Power chords.

Introduction:- Chopper is a static device. A variable dc voltage is obtained from a constant dc

voltage source. Also known as dc-to-dc converter. Widely used for motor control. Also used in

regenerative braking. Thyristor converter offers greater efficiency, faster response, lower maintenance,

smaller size and smooth controlA chopper is a high speed on/off semiconductor switch. It connects

source to load and disconnects the load from source at a fast speed.

Step Up chopper.

Step Down chopper.

Step Up Chopper:- In this converter Output Voltage is greater than input voltage. This is achieved byfast switching of a semiconductor device. The increase in output voltage depends on the frequency of

switching (i.e.) depends on pulse given to the device. While switch is off the output voltage almost same

as input. While switch is ON mosfet is assumed as short hence current flow in a shortest path so inductor

gets energized, and in continues flow we get output voltage greater than input.

Fig (a) Step up chopper circuit

PROCEDURE FOR DC STEP UP CHOPPER:-

Switch on the power for Kit.

Apply gate pulse from pulse generator

Connect DC supply (+12V or +5V) across input and CRO across the output of the

chopper..

Check whether DC voltage is varying from 0-30V.

Connections are made as shown in the circuit diagram.


11/14

Observe the output waveform at CRO and Vary input voltage and note down the reading

across load. Change the duty cycle of gate pulse using potentiometer and observe the

variations at output.

Repeat from last step for different values.

Calculate the output voltage using formula;

Graph of output voltage from CRO:-

Calculations and Result table for step up chopper circuit:-

Sl.no Input

voltage

Ton Toff Total

period

Step up

Output

voltage

Step down

Output

voltage

1 4 7 1.11

2 5 6 1.24

3 6 5 1.08

4 3 8 0.833

5 7 4

6 8 3


12/14

Step Down Chopper:- In this chopper Output Voltage is less than input voltage. This is achieved by

switching of a semiconductor device. The decrease in output voltage depends on the switch off and on

time. While device is off state it means there will not be any contact between load and input so the output

voltage will be zero. While device is On state there will the output voltage hence the loop continues.

Fig(b) Step down chopper circuit

Procedure for step down chopper circuit:-

1. Connect MOSFET or IGBT in the circuit to perform DC to DC chopping process.

2. Apply gate pulse from pulse generator.

3. Connect DC supply (+12V or +5V) across input and CRO across the output of thechopper.

4. Observe the output waveform at CRO.

5. Change the duty cycle of gate pulse using potentiometer and observe the variations at

output.

6. Here we can see how the output voltage changes according to the duty cycle of gate

pulse and it is always less than the input voltage.

7. Calculate the output voltage using formula;

Where = 1/T

8. Draw the graph of output voltage from CRO.


13/14

Graph of output voltage from CRO:-

Calculations and Result table for step down chopper circuit:-

Sl.no Input

voltage

Ton Toff Total

period

Step up

Output

voltage

Step down

Output

voltage

1 4 7

2 5 6

3 6 5

4 3 8

5 7 4

6 8 3

Disscusions and conculusion:- A starting circuit is required and the starting circuit should be such

that it triggers thyristor T2 first.Load voltage jumps to almost twice the supply voltage when the

commutation is initiated. The discharging and charging time of commutation capacitor are dependent on

the load current and this limits high frequency operation, especially at low load current.

Result: Thus Step Up and Step Down Chopper was constructed and verified with the graph and here we

can see how the output voltage changes according to the duty cycle of gate pulse and it is always greater

than the input voltage.


14/14

References

1.Electric Machinery, Fourth Edition, Fitzgerald, Kinglsey, and Umans,

McGraw-Hill Book Company, 1983, Chapter 1.

2. Electromagnetic and Electromechanical Machines, Matsch, Leander W., Intext

Educational Publishers, 1972.

3. Electromechanical Devices for Energy Conversion and Control Systems, Del

Toro, Vincent, Prentice-Hall, Inc., 1968.

4. http://seminarprojects.com/s/advantages-of-oc-test-and-sc-test-single-phase-transformer

5.Muhammad Mazidi & Janice Mazidi, January 2002, National Cheng Kung University Press, Hong

Kong.

6.Stan Gibilisco, G August 2005, Electrical Demystified, McGraw Hill Press, New York.7. Rashid, Muhammad H. Power Electronics. New Delhi: Prentice Hall of India Pvt Ltd,

2001.

8. Bimbhra, Dr P S. Power Electronics. New Delhi: Khanna Publisher, 2005.

9. Bimbhra, Dr P S. Electrical Machinery. New Delhi: Khanna Publisher, 1998.

10. Pendharkar Sameer, Trivedi Malay, Shenai Krishna, Electrothermal Simulations in

Punchthrough and Nonpunch through IGBTs, IEEE transactions on electron devices,

Vol. 45, no. 10, october 1998.

11. Yilmaz H., VanDell W R., Owyang K, and Chang M. F, Insulated gate transistor

modeling and optimization, in IEDM Tech. Dig., 1984, p. 274.

Final Epm15th April

Documents

Transcript of Final Epm15th April