LAB-MANUAL · AIETM/ Department of Electrical Engineering/EDTC Lab pg.-2 14. Exp-9 Control speed of...

AIETM/ Department of Electrical Engineering/EDTC Lab pg.-0

LAB-MANUAL

IV Year VIII SEM EE

8EE06

ELECTRICAL DRIVE &

CONTROL LAB

DEPARTMENT OF ELECTRICAL ENGINEERING


INDEX

S. NO. CONTENT PAGE NO.

1. RTU syllabus

2. Do’s and Don’ts

3. Instructions to the Students

4. Lab PEO

5. Lab Plan

6. Exp-1. Study and test the firing circuit of three phase half

controlled bridge converter.

7. Exp-2 Study and obtain waveforms of 3 phase half controlled

bridge converter with R and RL loads.

8. Exp-3 Study and test the firing circuit of 3-phase full controlled

bridge converter.

9. Exp-4. Study and obtain waveforms of 3-phase full controlled

bridge converter with R and RL loads.

10. Exp-5 Study and test 3-phase AC voltage regulator.

11. Exp-6 Control speed of dc motor using 3-phase half controlled

bridge converter. Plot armature voltage versus speed

characteristic.

12. Exp-7 Control speed of dc motor using 3-phase full controlled

bridge converter. Plot armature voltage versus speed

characteristic.

13

Exp-8 Control speed of a 3-phase induction motor in variable

stator voltage mode using 3-phase AC voltage regulator.


14. Exp-9 Control speed of universal motor using AC voltage

regulator.

15. Exp-10 Study 3-phase dual converter.

16. Exp-11. Study speed control of dc motor using 3-phase dual

converter.

17. Exp-12 Study three-phase cycloconverter and speed control of

synchronous motor using cycloconverter.

18. Exp-13 Control of 3-Phase Induction Motor in variable

frequency V/f constant mode using 3-phase inverter


Time Table Session: 2019-2020

Faculty: Mr. RAVI SHARMA

Mr. RAVINDER SINGH MAAN

Assot. Prof. & Head ,

Deptt. of EE

PERIOD/ DAY

I II III IV V VI VII VIII

MONDAY

TUESDAY

WEDNESDAY

THURSDAY

FRIDAY

SATURADAY


Detailed Syllabus

Class: VIII Sem. B.Tech. Evaluation

Branch: E.E

Schedule per Week

Practical Hrs : 2 hr/week

Examination Time = Three (3) Hours

Maximum Marks = 100

[Sessional (60) & End-term (40)]

S. No. List of Experiments as per RTU Syllabus

1. Exp-1. Study and test the firing circuit of three phase half controlled bridge

converter.

2. Exp-2 Study and obtain waveforms of 3 phase half controlled bridge

converter with R and RL loads.

3. Exp-3 Study and test the firing circuit of 3-phase full controlled bridge

converter.

4. Exp-4. Study and obtain waveforms of 3-phase full controlled bridge

converter with R and RL loads.

5. Exp-5 Study and test 3-phase AC voltage regulator.

6. Exp-6 Control speed of dc motor using 3-phase half controlled bridge

converter. Plot armature voltage versus speed characteristic.

7. Exp-7 Control speed of dc motor using 3-phase full controlled bridge

converter. Plot armature voltage versus speed characteristic.

8. Exp-8 Control speed of a 3-phase induction motor in variable stator voltage

mode using 3-phase AC voltage regulator.

9. Exp-9 Control speed of universal motor using AC voltage regulator.

10. Exp-10 Study 3-phase dual converter.

11. Exp-11. Study speed control of dc motor using 3-phase dual converter.

12. Exp-12 Study three-phase cycloconverter and speed control of synchronous

motor using cycloconverter.


13 Exp-13 Control of 3-Phase Induction Motor in variable frequency V/f

constant mode using 3-phase inverter

DO’S AND DONT’S

DO’S

1. Student should get the record of previous experiment checked before starting the new

experiment.

2. Read the manual carefully before starting the experiment.

3. Before starting the experiment, get circuit diagram checked by the teacher.

4. Before switching on the power supply, get the circuit connections checked.

5. Get your readings checked by the teacher.

6. Apparatus must be handled carefully.

7. Maintain strict discipline.

8. Keep your mobile phone switched off or in vibration mode.

9. Students should get the experiment allotted for next turn, before leaving the lab.

DONT’S

1. Do not touch or attempt to touch the mains power supply Wire with bare hands.

2. Do not overcrowd the tables.

3. Do not tamper with equipments.

4. Do not leave the without permission from the teacher.


INSTRUCTIONS TO THE STUDENTS

General Instructions

Maintain separate observation copy for each laboratory.

Observations or readings should be taken only in the observation copy.

Get the readings counter signed by the faculty after the completion of the

experiment.

Maintain Index column in the observation copy and get the signature of the

faculty before leaving the lab.

Before Entering the Lab

The previous experiment should have been written in the practical file, without

which the students will not be allowed to enter the lab.

The students should have written the experiment in the observation copy that they

are supposed to perform in the lab.

The experiment written in the observation copy should have aim, apparatus

required, circuit diagram/algorithm, blank observation table (if any), formula (if

any), programmed (if any), model graph (if any) and space for result.

When Working in the Lab

Necessary equipments/apparatus should be taken only from the lab assistant by

making an issuing slip, which would contain name of the experiment, names of

batch members and apparatus or components required.


Never switch on the power supply before getting the permission from the faculty.

Before Leaving the Lab

The equipments/components should be returned back to the lab assistant in good

condition after the completion of the experiment.

The students should get the signature from the faculty in the observation copy.

They should also check whether their file is checked and counter signed in the

index.


PROGRAM EDUCATION OBJECTIVES AND OUTCOMES

2019-2020

Subject Name/Code: 8EE6 Electrical Drives & Control Lab

Class: B. Tech. IV Yr VIII Sem. Electrical Engineering Practical: 2 hrs/week

External Marks: 40

Internal Marks: 60 Total Marks: 100

(1). Program Description: To offer high quality education in the field of Electrical

Engineering and to prepare students abreast of latest global industrial and research requirements

and fulfill responsibility towards community.

(2). Program Objective:

I. Preparation: To pursue graduate studies in Electrical Engineering and the crucial task to

identify, understand, and interpret the constraints on a design of the electrical system in

order to produce a successful result, not enough to build a technically successful product

but also to meet further energy requirements. playing an important role in maintaining

ethical standards of professionalism with a broad-based education in core areas of

Electrical Engineering, including theoretical foundations, experimentation and technical

implementation, with an appropriate blend of theory and practical’s so that the student is

able to comprehend and pinpoint problems in the fields of Electrical Engineering.

II. Core competence: To provide students the creative application of scientific principles to

design or develop structures, machines, apparatus or works and utilizing them in present

day scenario of fields related to electricity such as generation, transmission and

distribution and construct or operate the same with full cognizance of their design or to

forecast their behavior under specific operating conditions in core areas of Electrical

Engineering. Student will be able to employ necessary techniques, hardware, and tools


for modern engineering applications and student can solve problems through analytical

thinking in their own or related fields.

III. Breadth: To train students with good scientific and technical breadth so as to embody

inventions and put his ideas in concrete terms and design something that promotes and

helps in fulfilling the ever expanding energy requirements. To develop any device,

gadget, material, method, an innovative experiment, a new solution to a problem, or an

improvement on what is existing in the present electrical system.

IV. Professionalism: To inculcate in students professional and ethical attitude,

Communication Skills, teamwork Skills, computer programming skill and an ability to

relate engineering issues to broader social context. To develop in the students their

learning interaction and tacit knowledge transfer influenced by individual and collective

thinking styles and mental depositions. The cognitive style of electrical engineering and

technically knowledgeable issues for the new systems of innovation in his field.

V. Learning Environment: To provide the excellent learning environment, which can

enhance the learning ability of student to generate awareness of surrounding,

attentiveness to details, experimental thoroughness and practicality that are the hallmarks

of tasks requiring a conglomeration of concrete information and abstract concept to help

individuals, complete society and nation?

(3)Program Outcomes:

A. Graduates will demonstrate knowledge of advanced mathematics, science and electrical

engineering with the ability to apply the theoretical knowledge and concepts to the

disciplines of electrical engineering.

B. Graduates will demonstrate an ability to identify, formulate, pinpoint and solve Electrical

engineering problems keeping in view the present day power and energy requirement and

its future prospect.

C. Graduate will demonstrate an ability to design electrical and power electronic circuits and

conduct experiments that serve as the blue print for the complex electrical circuitry


associated with our day to day electricity transmission and protection process related with

power systems, analysis, protection and distribution.

D. Graduates will demonstrate an ability to design study and analyze the digital and analog

systems and components that serve as the fundamental components of the power

engineering methods being increasingly used with the new technological advances.

E. Graduates will demonstrate an ability to visualize and work on laboratory and Identify the

theoretical models as predictors of real world behavior. This may include evaluating,

establishing of validating a relationship between data and underlying physical principles.

F.

Graduate will demonstrate skills to use modern engineering tools, software, equipment to

design, protect or assemble the system using specific methodologies with the help of

appropriate tools to satisfy requirements.

G. Graduates will demonstrate knowledge of professional and computer language skills that

will eventually develop them into skilled researchers in an atmosphere that is technically

advanced and conductive.

H. Graduate will be able to communicate effectively in both verbal and written form. They

will develop a better presentation skill on academic and personal grounds that will enhance

their personality in all aspects.

I. Graduate will understand the impact of engineering solutions on the society and also be

aware of contemporary issues relating to the exhausting resources and alternatives to

continue uninterrupted power supply.

J. Graduate will develop confidence, self motivation, positive belief, consistency,

perseverance and team work.

K. Graduate will be able to participate and succeed in campus placements and competitive

examinations like Public sector, GATE, GRE etc.


(4) Mapping of Program Objective with Program Outcome

(5) Course Objective

After studied Power Electronics-III in their graduation plan, student will be able to

1. The course gives a deep view of all power device used in industries and also gives the

reason for their use in particular application. The subject also helps in monitoring of a

particular circuitry by studying its switching characteristics.

2. The course gives an overview about the different forms of inverters & rectifiers & also

explains their use in industries for a particular application.

3. The course describes about different forms of power supplies like ups, smps high

frequency electronic ballast etc. course also gives the reason that why a particular supply

is better for a specific application.

4. The course consists of study of various power drives & also includes various types of

circuitries for controlling power drives. Here controlling means various factors associated

with drive like its speed.

Program

Objective

Program Outcomes

A B C D E F G H I J K

I √ √ √ √ √ √

II √ √ √ √ √ √ √ √

III √ √ √ √ √ √ √ √

IV √ √ √ √ √ √ √

V √ √ √ √ √ √


5. The course also covers the study of various types of stepper motors with their specific

application like variable reluctance type, permanent magnet & reluctance type & hybrid.

(6) Course Outcomes:-

The course tends to improvise the students and provides the basic and deep knowledge and

development of a strong building block of Power Electronics.

I. Power Electronics engineering is an interdisciplinary field so engineering personnel’s my

find difficulties in industrial terminology & vice –versa. So the learners will be able to

understand either engineering terminology in industrial environment.

II. Learners will also be able to understand about the various electronic devices used in

industries.

III. After studying the devices, the learner will be able to analyze the application of each

device.

IV. The learners will also be able to find that why these devices are eligible to use in

industries.

V. Students will also get that what makes these devices to be used in industrial environment

by studying its structure.

VI. After study of all the devices learners will also be able to understand the circuitry

associated with these devices.

VII. Learners will also be able to understand the mechanism/instrumentation involved in

particular circuit.

VIII. Learners will also be able to understand the use of different types of power supplies used

in industrial environment.

IX. Learners will be able to get the idea about different types of stepper motors & also able to

understand the mechanism to control the parameters associated with Controller.


X. Learners will also be able to know the applications of different forms of rectifier,

choppers & inverters & different configurations associated with them.

(7) Mapping of Course Objective with Course Outcome

(8) Course Objective Contribution to Program Outcomes

Students who have successfully completed this course will have full understanding of following

concepts.

Program

Objective

Program Outcomes

I. II. III. IV. V. VI. VII. VIII. IX. X.

I √ √ √ √ √ √

II √ √ √ √ √ √ √

III √ √

IV √ √

V √ √ √ √ √ √

COURSE OBJECTIVE PROGRAM OUTCOME

1. C

ourse gives a deep view of all

power device used in industries

and also gives the reason for

their use in particular

application. The subject also

A. Graduates will demonstrate knowledge of advanced

mathematics, science and electrical engineering with the

ability to apply the theoretical knowledge and concepts

to the disciplines of electrical engineering.

B. Graduates will demonstrate an ability to identify,

formulate, pinpoint and solve Electrical engineering

problems keeping in view the present day power and

energy requirement and its future prospect.


helps in monitoring of a

particular circuitry by studying

its switching characteristics.

2. T

he course gives an overview

about the different forms of

inverters & rectifiers & also

explains their use in industries

for a particular application.

3. T

he course describes about

different forms of power supplies

like ups, smps high frequency

electronic ballast etc. course also

gives the reason that why a

particular supply is better for a

specific application.

4. T

he course consists of study of

various power drives & also

includes various types of

circuitries for controlling power

drives. Here controlling means

various factors associated with

drive like its speed.

C. G

raduate will demonstrate an ability to design electrical

and power electronic circuits and conduct experiments

that serve as the blue print for the complex electrical

circuitry associated with our day to day electricity

transmission and protection process related with power

systems, analysis, protection and distribution.

D. G

raduates will demonstrate an ability to design study and

analyze the digital and analog systems and components

that serve as the fundamental components of the power

engineering methods being increasingly used with the

new technological advances.

E. G

raduates will demonstrate an ability to visualize and

work on laboratory and Identify the theoretical models

as predictors of real world behavior. This may include

evaluating, establishing of validating a relationship

between data and underlying physical principles.

F. G

raduate will demonstrate skills to use modern

engineering tools, software, equipment to design,

protect or assemble the system using specific

methodologies with the help of appropriate tools to

satisfy requirements.

G. G

raduates will demonstrate knowledge of professional

and computer language skills that will eventually

develop them into skilled researchers in an atmosphere

that is technically advanced and conductive.

H. G

raduate will be able to communicate effectively in both

verbal and written form. They will develop a better

presentation skill on academic and personal grounds that

will enhance their personality in all aspects.

I. Graduate will understand the impact of engineering

solutions on the society and also be aware of

contemporary issues relating to the exhausting resources


(9) Course Objective to Program Outcomes mapping.

(10) Topics Covered Beyond the Curriculum:-Along-with the above stated topics allotted in

the syllabus we covered following topics in this subject which are important for the Circuit

Analysis & Synthesis:

5. The course also covers the study

of various types of stepper

motors with their specific

application like variable

reluctance type, permanent

magnet & reluctance type &

hybrid.

and alternatives to continue uninterrupted power supply.

J. Graduate will develop confidence, self motivation,

positive belief, consistency, perseverance and team

work.

K. G

raduate will be able to participate and succeed in

campus placements and competitive examinations like

Public sector, GATE, GRE etc.

COURSE

OBJECTIVE

Program Outcomes

A B C D E F G H I J K

I √ √ √ √ √ √ √ √

√

II √ √ √ √ √ √ √

III √ √ √ √ √

IV √ √ √ √ √ √ √

V √ √ √ √ √ √

Unit Beyond Syllabus topic Source

I Study and obtain the waveforms for voltage-commutated

chopper. Study Through Manual

II Study and obtain the waveforms for current-commutated

chopper. Study Through Manual


(11) Text and Reference Books:-

1. Text books:

1 Electrical Drives & Their Control

By G.K. Dubey

2 Power Electronics

By J.S Chitode

3 Power Electronics

4 Power Electronics

By M. H. Rashid

2. Reference books:-

Fundamentals of power electronics

By Robert Warren Erickson, Dragan Maksimović

Power electronics: converters, applications, and design

By Ned Mohan, Tore M. Undeland

Power electronics: principles and applications

By Joseph Vithayathi

(12) Instructional Methods:-

1. Direct Instructions:

I Black board presentation

II PowerPoint presentation

III Multimedia like video lectures

http://books.google.co.in/books?id=eS1z95mzi28C&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CFMQ6AEwBA

http://books.google.co.in/books?id=0_D6gfUHjcEC&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CD8Q6AEwAQ

http://books.google.co.in/books?id=eS1z95mzi28C&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CFMQ6AEwBA

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22M.+H.+Rashid%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CFQQ9Ag

http://books.google.co.in/books?id=On9-rJTR8ygC&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CDgQ6AEwAA

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Robert+Warren+Erickson%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CDkQ9Ag

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Robert+Warren+Erickson%22&q=inauthor:%22Dragan+Maksimovi%C4%87%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CDoQ9Ag

http://books.google.co.in/books?id=oxR8vB2XjgIC&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CEYQ6AEwAg

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Ned+Mohan%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CEcQ9Ag

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Ned+Mohan%22&q=inauthor:%22Tore+M.+Undeland%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CEgQ9Ag

http://books.google.co.in/books?id=LX5GKpQz2CgC&printsec=frontcover&dq=power+electronics&hl=en&sa=X&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CHAQ6AEwCQ

http://www.google.co.in/search?hl=en&sa=G&tbo=1&tbm=bks&tbm=bks&q=inauthor:%22Joseph+Vithayathil%22&ei=wwY2T4HXG8XmmAXyt_2kAg&ved=0CHEQ9Ag


2. Interactive Instruction:

I Think, pair, share

3 .Indirect Instructions:

I Social networking

4. Independent Instructions:

I Assigned questions

(13) Learning Materials:-

1. Text/lecturer notes/ lecturer PPT

2. Multimedia material (videos, text with animations)

3. Lab Manuals

(14) Web Resources :-

1. www. nptel.iitm.

2. www.youtube.com

3. ieeexplore.ieee.org

(15) Assessment Of Outcomes:-

1. Sessional tests (two in each semester and assessment is done on the basis of average of

marks.)

2. End term exam (Conducted by RTU, KOTA)

3. Surprise Quiz/ Tests.

4. Presentation by students.

5. Daily class room interaction.

6. Assignments.

(16) Outcomes will be achieved through following:-

1. Class room teaching (through chalk and board and PPT).

2. Discussion on case- studies.


3. Expert lectures from industries/ Academies.

4. Suggested research papers.

5. Video lectures through NPTEL.

EXPERIMENT # 1

OBJECT: Study and test the firing angle circuit of three phase half controlled bridge converter.

APPARATUS REQUIRED:

S. No. Name of Apparatus Type Range Quantity

1

3-phase Half

controlled bridge

converter kit

415V, 20Amp, 50Hz 1

2 CRO 230V, 350mA, 50Hz 1

3 Connecting Leads - As per

requirement

4 CRO Probe 1

THEORY:

Introduction

The proper design of firing circuits yields precise, reliable and stable operation of the system.

Simplicity, small size, minimum number of components and lower cost are generally the most

important factors that determine a good design. Different methods are commonly used to

construct firing circuits for triggering thyristers. Each method has advantages and disadvantages.

The firing circuit that is introduced in does not meet with all requirements for good

design. Minimum components and synchronized control are used in circuit but the disadvantage


of this circuit is that it uses a single chip as decoder so that any damage in the decoder will make

the circuit fail to supply firing pulses, as well as the firing angle is not vary linearly with the dc

control voltage. The proposed controller for thyrsiter control, which is produced in, is in

agreement with the requirements for good design, but it is used for single-phase circuit.In this

work good circuit design is introduced where less components are used, linear relationship

between triggering angle and the control voltage, besides synchronized with the supply voltage.

The firing circuit is designed, assembled, and tested. The firing angle can be varied from 0 to 180

by changing the control voltage from 0 to 70 mv.

Firing Circuit Description And Design

The main object of the converter circuit under consideration is to deliver three gate pulses

separated by 1200 to the thyristers gates with sufficient width time in order to turn on, also

synchronism with the supply voltages, and can be varied along the positive half cycle of the

thyrister anode cathode voltages. Fig. (1) illustrates the block diagram of the firing circuit, it

mainly consists of five stages. Square wave generator, ramp generator, voltage comparator, pulse

splitter, and pulse isolator. The schematic of the complete firing circuit is shown in fig. (2), with

its typical waveforms for different stages shown in Fig. (3).The square wave generator comprises

three step-down transformers connected as shown in Fig.(2),in order to get reference voltages at

a,b,c.The firing pulses to th1 will be explained below in details. The secondary voltage of

transformer vag is compared with zero level voltage using IC741 op amp. The output of this

comparater i.e. point (d) is fed to stage two ramp generator, it consists of RC integrator with pnp

transistor switch across capacitor for sharp discharge. Values of R and C must be chosen large

enough to give approximately linear rise for the ramp. However with larger values of R and C

the maximum value of capacitor voltage will be low during the charging interval which is taken

10 msec width. The output ramp function at point (e) is fed to stage three i.e. voltage comparator

in order to permits variation of firing angle with respect to controlled voltage VR. In stage four

the output pulses at point (f) is frequency modulated using pulse splitter IC7411 and IC555 timer

to generator pulses at frequency 2khz .The aim of injecting high frequency pulses is to make the

firing signal exists for a time enough to ensure realizable turn on and without excessive gate

power desperation. Finally the frequency-modulated pulses at point (g) is applied to the thyrister

gate through an opto-coupler IC CNY48 in stage six. 3-Experimental Results The firing circuit

shown in Fig.(2) is assembled and tested. Waveforms are photographed for different positions.

Fig.(4) illustrates the waves at points(a,d) while Fig.(5) shows the waves at points(d,e).Fig.(6)

shows combination of all the waveforms at different points of the firing circuit. It is easy to

compare the relative phase difference between the different waveforms. This firing circuit is

tested for a three phase half controlled bridge rectifier to control the speed of dc motor. The

firing angle can be varied from (0-1800) by adjusting the control voltage VR from (0-70) mV.

Fig.(7) shows the experimental firing angle verses the control voltage curve .Fig.(8) illustrates

the firing angle verses motor speed characteristics of the dc motor.

Conclusion

The firing circuit for three-phase thyrister bridge rectifier have been designed and controlled in

laboratory. The firing angle can be varied from (0-1800) according to change in control voltage


of the comparator. Various waveforms of the firing circuit are obtained in laboratory and

oscillagraphed.

Wave form output for different stages of firing

PROCEDURE:

1. Connect the firing circuit by connecting leads.

2. Connect the CRO at output terminals.

3. Switch On the supply.

4. Take the output waveform for different types of firing circuits.

RESULT: Thus we have studied and observed the waveform output for different firing circuit.

PRECAUTIONS:


1. No loose connection is allowed.

2. Switch on the Supply after checking the connections by faculty/Lab assistant.

3. Take the observation carefully.

4. Don’t touch any live part or wire, it may be dangerous.


VIVA QUIZ

1. What do you mean by the term firing?

2. What will be on state voltage drop across SCRs of 3-phase half controlled bridge converter?

3. What is reverse blocking mode?

4. What is the difference between the firing circuit of three phase half controlled converter and

three phase full controlled converter?

5. How do you provide firing to SCR?

6. What is the importance of firing circuit?

7. What will be the circuit turn off time of three phase half controlled converter?

8. What is the difference between R and RC firing circuit?

9. What is the difference between the firing circuit of three phase half controlled converter and

single phase half controlled converter?

10. What is forward conduction mode?

11. What is RC firing circuit?

12. What is the alternate of firing?

13. How many types of firing circuit we have?

14. What do you understand by PWM?

15. What is firing angle delay?

16. What is the order of leakage current in SCR?

----------------------------------


EXPERIMENT # 2

OBJECT: Study and obtain waveforms of 3 phase half controlled bridge converter with R and

RL loads.

APPARATUS REQUIRED:

S.No. Name of Apparatus Type Range Quantity

1

3-phase Half

controlled bridge

converter kit

415V, 20Amp, 50Hz 1

2 CRO 230V, 350mA, 50Hz 1


requirement

4 Multi meter Digital

5 CRO Probe 1

THEORY:

Three phase fully controlled converters are very popular in many industrial applications

particularly in situations where power regeneration from the dc side is essential. It can handle

reasonably high power and has acceptable input and output harmonic distortion. The

configuration also lends itself to easy series and parallel connection for increasing voltage and

current rating or improvement in harmonic behavior. However, this versatility of a three phase

fully controlled converters are obtained at the cost of increased circuit complexity due to the use

of six thyristors and their associated control circuit. This complexity can be considerably reduced

in applications where power regeneration is not necessary. In those case three thyristors of the

top group or the bottom group of a three phase fully controlled converter can be replaced by

three diodes. The resulting converter is called a three phase half controlled converter. Replacing

three thyristors by three diodes reduces circuit complexity but at the same time prevents negative


voltage appearing at the output at any time. Therefore the converter cannot operate in the

inverting mode.

The three phase half controlled converter has several other advantages over a three phase

fully controlled converter. For the same firing angle it has lower input side displacement factor

compared to a fully controlled converter. It also extends the range of continuous conduction of

the converter.

It has one serious disadvantage however. The output voltage is periodic over one third of

the input cycle rather than one sixth as is the case with fully controlled converters. This implies

both input and output harmonics are of lower frequency and require heavier filtering. For this

reason half controlled three phase converters are not as popular as their fully controlled

counterpart.

Although, from the point of view of construction and circuit complexity the half

controlled converter is simpler compared to the fully controlled converter, its analysis is

considerably more difficult. In this lesson the operating principle and analysis of a three phase

half controlled converter operating in the continuous conduction mode will be presented.

Circuit Diagram of Three phases half controlled Bridge Converter

PROCEDURE:

1. Connect the circuit of 3-phase half controlled bridge converter by connecting leads.

2. Connect the load terminals with R or RL load as per required.

3. Connect the CRO with kit to get the result waveform.


4. Switch On the supply carefully.

5. Find and trace the output waveform on trace paper for different firing angles by varying

the firing angle knob.

RESULTS:

Output is obtained on CRO

(i) Connecting with Resistive load


(ii) Connecting with RL load


PRECAUTIONS:





VIVA QUIZ:

1. What do you understand by the term half controlled converter?

2. What will be the output voltage in case of 3 phase half controlled converter?

3. What is the difference between R and RL bridge circuit?

4. During the negative half cycle of AC supply o/p current will available or not?

5. What is the effect of inductive load when connected in circuit?

6. What is the difference between three phase half controlled converter and three phase full

controlled converter?


8. How many diodes and SCRs are used in 3-phase full controlled bridge converter?

9. What will be on state voltage drop across SCRs of 3-phase half controlled bridge converter?

10. What are the applications of half wave controlled converter?

11. What is the current rating for SCRs used in half controlled converter?

12. How a half controlled single phase converter is different from three phase controlled converter?

13. What will be the effect on efficiency of bridge converter on replacing the diodes with SCR?

14. What are the draw backs of half controlled converter?

15. What are the advantages of half controlled converter?

--------------------------------

http://wiki.answers.com/Q/Uses_of_half_wave_rectifier


EXPERIMENT # 3

OBJECT: Study and test the firing angle circuit of three phase full controlled bridge converter.

APPARATUS REQUIRED:


1

3-phase full

controlled bridge

converter kit

415V, 20Amp, 50Hz 1

2 CRO 230V, 350mA, 50Hz 1


requirement

4 CRO Probe 1

THEORY:

Introduction

The proper design of firing circuits yields precise, reliable and stable operation of the system.

Simplicity, small size, minimum number of components and lower cost are generally the most

important factors that determine a good design. Different methods are commonly used to

construct firing circuits for triggering thyristers. Each method has advantages and disadvantages.

The firing circuit that is introduced in does not meet with all requirements for good

design. Minimum components and synchronized control are used in circuit but the disadvantage

of this circuit is that it uses a single chip as decoder so that any damage in the decoder will make

the circuit fail to supply firing pulses, as well as the firing angle is not vary linearly with the dc

control voltage. The proposed controller for thyrsiter control, which is produced in, is in

agreement with the requirements for good design, but it is used for single-phase circuit.In this

work good circuit design is introduced where less components are used, linear relationship

between triggering angle and the control voltage, besides synchronized with the supply voltage.

The firing circuit is designed, assembled, and tested. The firing angle can be varied from 0 to 180

by changing the control voltage from 0 to 70 mv.

Firing Circuit Description and Design


The main object of the converter circuit under consideration is to deliver three gate pulses

separated by 1200 to the thyristers gates with sufficient width time in order to turn on, also

synchronism with the supply voltages, and can be varied along the positive half cycle of the

thyrister anode cathode voltages. Fig. (1) illustrates the block diagram of the firing circuit, it

mainly consists of five stages. Square wave generator, ramp generator, voltage comparator, pulse

splitter, and pulse isolator. The schematic of the complete firing circuit is shown in fig. (2), with

its typical waveforms for different stages shown in Fig. (3).The square wave generator comprises

three step-down transformers connected as shown in Fig.(2),in order to get reference voltages at

a,b,c.The firing pulses to th1 will be explained below in details. The secondary voltage of

transformer vag is compared with zero level voltage using IC741 op amp. The output of this

comparater i.e. point (d) is fed to stage two ramp generator; it consists of RC integrator with pnp

transistor switch across capacitor for sharp discharge. Values of R and C must be chosen large

enough to give approximately linear rise for the ramp. However with larger values of R and C

the maximum value of capacitor voltage will be low during the charging interval which is taken

10 msec widths. The output ramp function at point (e) is fed to stage three i.e. voltage

comparator in order to permits variation of firing angle with respect to controlled voltage VR. In

stage four the output pulses at point (f) is frequency modulated using pulse splitter IC7411 and

IC555 timer to generator pulses at frequency 2khz .The aim of injecting high frequency pulses is

to make the firing signal exists for a time enough to ensure realizable turn on and without

excessive gate power desperation

Wave form output for different stages of firing

Voltage waveform for stage-1


Voltage waveform for stage-2

PROCEDURE:

1. Connect the firing circuit by connecting leads.

2. Connect the CRO at output terminals.

3. Switch On the supply.

4. Take the output waveform for different types of firing circuits.

RESULT: Thus we have studied and observed the waveform output for different firing circuit.

PRECAUTIONS:






VIVA QUIZ

1. What do you understand by the term firing of SCR?

2. What is resistance firing circuit?

3. What is holding current?

4. What is forward blocking mode?

5. What is firing angle delay?

6. What is the order of leakage current in SCR?


8. What will be the average output voltage in case of three phase full controlled converter?

9. What will be on state voltage drop across SCRs of 3-phase full controlled bridge converter?

10. What is the difference between the firing circuit of three phase full controlled converter and

single phase full controlled converter?

11. What is range of angle control in resistance firing circuit?

12. What do you understand by UJT firing circuit?

13. Which type of firing is most suitable?

14. What is the importance of firing circuit?

15. What do you know about RC firing circuit?


EXPERIMENT # 4

OBJECT: Study and obtain waveforms of 3 phase full controlled bridge converter with R and

RL loads.

APPARATUS REQUIRED:


1

3-phase full

controlled bridge

converter kit

415V, 20Amp, 50Hz 1

2 CRO 230V, 350mA, 50Hz 1


requirement

4 Multi meter Digital

5 CRO Probe 1

THEORY:

The three phase fully controlled bridge converter has been probably the most widely used power

electronic converter in the medium to high power applications. Three phase circuits are

preferable when large power is involved. The controlled rectifier can provide controllable out put

dc voltage in a single unit instead of a three phase autotransformer and a diode bridge rectifier.

The controlled rectifier is obtained by replacing the diodes of the uncontrolled rectifier with

thyristors. Control over the output dc voltage is obtained by controlling the conduction interval

of each thyristor. This method is known as phase control and conver ters are also called “phase

controlled converters”. Since thyristors can block voltage in both directions it is possible to

reverse the polarity of the output dc voltage and hence feed power back to the ac supply from the

dc side. Under such condition the converter is said to be operating in the “inverting mode”. The

thyristors in the converter circuit are commutated with the help of the supply voltage in the

rectifying mode of operation and are known as “Line commutated converter”. The same circuit


while operating in the inverter mode requires load side counter emf. for commutation and are

referred to as the “Load commutated inverter”.

In phase controlled rectifiers though the output voltage can be varied continuously the

load harmonic voltage increases considerably as the average value goes down. Of course the

magnitude of harmonic voltage is lower in three phase converter compared to the single phase

circuit. Since the frequency of the harmonic voltage is higher smaller load inductance leads to

continuous conduction. Input current wave shape become rectangular and contain 5th

and higher

order odd harmonics. The displacement angle of the input current increases with firing angle.

The frequency of the harmonic voltage and current can be increased by increasing the pulse

number of the converter which can be achieved by series and parallel connection of basic 6 pulse

converters. The control circuit become considerably complicated and the use of coupling

transformer and / or inter phase reactors become mandatory.

Circuit Diagram of Three phases Full controlled Bridge Converter

PROCEDURE:

1. Connect the circuit of 3-phase full controlled bridge converter by connecting leads.

2. Connect the load terminals with R or RL load as per required.

3. Connect the CRO with kit to get the result waveform.

4. Switch On the supply carefully.


5. Find and trace the output waveform on trace paper for different firing angles by varying

the firing angle knob.

RESULTS:

Output is obtained on CRO

PRECAUTIONS:





VIVA QUIZ

1. How many SCRs are used in 3-phase full controlled bridge converter?


3. What are filter?

4. How the output voltage of half wave controlled converter gets affected when the R load is

replaced with R-L load?

5. What will be the output voltage of half wave controlled converter for R load?

6. Which type of input is applied to the gate terminal of the controlled converter?

7. Is there any harmonics content available in output obtained in full controlled converter?

8. Which type of input is applied to the gate terminal of the controlled converter?

9. What is the use of firing angle in the three phase full controlled converter?

10. What is the difference between three phase half controlled converter and three phase full

controlled converter?

11. What are the draw backs of full controlled converter?

12. Why should we use full controlled converter while we have half controlled converter?

13. For full controlled converter which component is used whether diode or SCRs?

14. What are the advantages of full controlled converter?

15. What is the difference between three phase full controlled converter and three phase full wave

converter?

-------------------------------

http://www.ask.com/questions-about/Half-Wave-Rectifier#anc_2

http://www.ask.com/questions-about/Half-Wave-Rectifier#anc_2


EXPERIMENT # 5

OBJECTIVE: Study and test 3-phase AC voltage regulator

APPARATUS REQUIRED:


1. AC voltage Regulator kit 415V, 50Hz 1

2. Auto-Transformer 3-phase 0-400V 1

3. Lamp-Load 10W 3

4. Connecting Leads -

As per

requirement

5. Multi meter Digital

THEORY:

Three-phase AC Regulators

There are many types of circuits used for the three-phase ac regulators (ac to ac voltage

converters), unlike single-phase ones. The three-phase loads (balanced) are connected in star or

delta. Two thyristors connected back to back, or a triac, is used for each phase in most of the

circuits as described.

Three-phase, AC Voltage Regulator with Balanced Resistive Load

The circuit of a three-phase, three-wire ac regulator (termed as ac to ac voltage converter) with

balanced resistive (star-connected) load is shown. It may be noted that the resistance connected

in all three phases are equal. Two thyristors connected back to back are used per phase, thus

needing a total of six thyristors. Please note the numbering scheme, which is same as that used in

a three-phase full-wave bridge converter or inverter, described in module 2 or 5. The thyristors

are fired in sequence), starting from 1 in ascending order, with the angle between the triggering

of thyristors 1 & 2 being (one-sixth of the time period (°60T) of a complete cycle). The line

frequency is 50 Hz, with fT/1==20 ms. The thyristors are fired or triggered after a delay of α

from the natural commutation point. The natural commutation point is the starting of a cycle with


period, (6/60T=°) of output voltage waveform, if six thyristors are replaced by diodes. Note that

the output voltage is similar to phase-controlled waveform for a converter, with the difference

that it is an ac waveform in this case. The current flow is bidirectional, with the current in one

direction in the positive half, and then, in other (opposite) direction in the negative half. So, two

thyristors connected back to back are needed in each phase. The turning off of a thyristor occurs,

if its current falls to zero. To turn the thyristor on, the anode voltage must be higher that the

cathode voltage, and also, a triggering signal must be applied at its gate.

Three-phase Four wire AC voltage regulator

PROCEDURE:

1. Connect the voltage regulator circuit by connecting leads.

2. Connect the star connected three lamps at the load terminals.

3. Connect the multi-meter as voltmeter.

4. Switch On the supply through 3-phase Auto-Transformer.


5. Measure the voltage variation with changing the firing angle control.

OBSERVATION TABLE:

Sr. No Firing Angle

Terminal Voltage

V (Volts)

1

2

3

4

RESULTS: Thus we have studied AC voltage regulator and measured the voltage variation with

firing angle control.

PRECAUTIONS:






VIVA QUIZ

1. What do you mean by voltage regulator?

2. Why we use AC voltage regulator?

3. Can we have DC voltage regulator?

4. How does AC voltage regulator works?

5. What are the fields of its application?

6. What is the working principle of AC voltage regulator?

7. How does it different from cycloconverter?

8. How many circuit configurations available for AC voltage regulator?

9. What is the difference between the output of half controlled & full controlled voltage regulator?

10. What is the difference between circuit configuration of single phase and three phase voltage

regulator?

11. How the voltage does vary in voltage regulator?

12. What type of output is obtained by AC voltage regulator?

13. Can we have single phase AC voltage regulator?

14. What are the types of three phase AC voltage regulator?

15. Which type of voltage regulator is best?

-------------------------------------


EXPERIMENT #6

OBJECT: Study speed control of DC motor using 3-phase half controlled bridge converter. Plot

armature voltage versus speed curve.

APPARATUS REQUIRED:


1

Half controlled

converter- Motor

control kit

200V, 15Amp, 50Hz 1


requirement

3 Multi meter Digital 1

4 Techo-meter Digital 1

5 DC motor shunt 230V, 1500rpm, 2.3Amp 1

6 Auto-Transformer 3-phase 0-400V 1

THEORY:

Speed Control of D.C. Shunt Motors

The speed of a shunt motor can be changed by

flux control method

armature control method

voltage control method.

The first method (i.e. flux control method) is frequently used because it is simple and

inexpensive

1. Flux control method

It is based on the fact that by varying the flux f, the motor speed (N µ 1/f) can be changed and

hence the name flux control method.

Advantages

(i) This is an easy and convenient method.

(ii) It is an inexpensive method since very little power is wasted in the shunt field rheostat due to

relatively small value of Ish.

(iii) The speed control exercised by this method is independent of load on the machine.


Disadvantages

(i) Only speeds higher than the normal speed can be obtained since the total field circuit

resistance cannot be reduced below Rsh—the shunt field winding resistance.

(ii) There is a limit to the maximum speed obtainable by this method. It is because if the flux is

too much weakened, commutation becomes poorer.

Note. The field of a shunt motor in operation should never be opened because its speed will

increase to an extremely high value.

2. Armature control method

This method is based on the fact that by varying the voltage available across the armature, the

back e.m.f and hence the speed of the motor can be changed. This is done by inserting a variable

resistance RC (known as controller resistance) in series with the armature.

Disadvantages

(i) A large amount of power is wasted in the controller resistance since it carries full armature

current Ia.

(ii) The speed varies widely with load since the speed depends upon the voltage drop in the

controller resistance and hence on the armature current demanded by the load.

(iii) The output and efficiency of the motor are reduced.

(iv) This method results in poor speed regulation.

3. Voltage control method

In this method, the voltage source supplying the field current is different from that which

supplies the armature. This method avoids the disadvantages of poor speed regulation and low

efficiency as in armature control method. However, it is quite expensive. Therefore, this method

of speed control is employed for large size motors where efficiency is of great importance.

Half controlled converter

Three phase fully controlled converters are very popular in many industrial applications

particularly in situations where power regeneration from the dc side is essential. It can handle

reasonably high power and has acceptable input and output harmonic distortion. The

configuration also lends itself to easy series and parallel connection for increasing voltage and

current rating or improvement in harmonic behavior. However, this versatility of a three phase

fully controlled converters are obtained at the cost of increased circuit complexity due to the use

of six thyristors and their associated control circuit. This complexity can be considerably reduced

in applications where power regeneration is not necessary. In that case three thyristors of the top


group or the bottom group of a three phase fully controlled converter can be replaced by three

diodes. The resulting converter is called a three phase half controlled converter. Replacing three

thyristors by three diodes reduces circuit complexity but at the same time prevents negative

voltage appearing at the output at any time. Therefore the converter cannot operate in the

inverting mode.

Speed control of DC motor by half controlled converter

PROCEDURE:

1. Connect the motor control circuit by connecting leads.

2. Connect the DC shunt motor at the load terminals.



5. Measure the motor speed using Techo-meter for different voltages by varying the firing

angle knob.


OBSERVATION TABLE:

RESULT:

Thus we have performed the speed control operation of DC shunt motor by using half controlled

converter.

PRECAUTIONS:





S.No.

S. No.

Voltage

(V)

Motor Speed

rpm

1

2

3


VIVA QUIZ:

1. Is it possible to obtain speeds above rated speed by the armature voltage control method?

2. Is it possible to obtain a reversal in speed by either the armature resistance or field control

method?

3. In D.C. shunt motors for speed control the resistance is inserted in armature circuit. Why?

4. What is harmonics? How it introduces in the DC output of converter?

5. How the harmonics are minimized during the conversion process of AC to DC?

6. What do you understand by the term filter? Filters are of how many types?

7. What is the difference between speed control and speed regulation of a motor?

8. How many SCRs are used in 3-phase half controlled bridge converter?

9. Which method of speed control provides constant horse power derive?

10. Which method of speed control provides constant torque derive?

11. What are the methods of speed control of DC motor?

12. Which parameter is varied in bridge converter method?

13. What is the shape of speed torque curve for DC shunt motor?

14. Which type of motor can be controlled by bridge converter method?

15. Can we control self-excited dc motor by using this method?


EXPERIMENT # 7

OBJECT: Study speed control of DC motor using 3-phase full controlled bridge converter. Plot

armature voltage versus speed curve.

APPARATUS REQUIRED:


1

Full controlled

converter- Motor

control kit

200V, 15Amp, 50Hz 1


requirement



5 DC motor shunt 230V, 1500rpm, 2.3Amp 1


THEORY:



flux control method




inexpensive





Advantages





Disadvantages





Note. The field of a shunt motor in operation should never be opened because its

speed will increase to an extremely high value.





Disadvantages

(i) A large amount of power is wasted in the controller resistance since it Carries full armature

current Ia.










Full controlled converter

The three phase fully controlled bridge converter has been probably the most widely used power

electronic converter in the medium to high power applications. Three phase circuits are

preferable when large power is involved. The controlled rectifier can provide controllable output


dc voltage in a single unit instead of a three phase autotransformer and a diode bridge rectifier.

The controlled rectifier is obtained by replacing the diodes of the uncontrolled rectifier with

thyristors. Control over the output dc voltage is obtained by controlling the conduction interval

of each thyristor. This method is known as phase control and converters are also called “phase

controlled converters”. Since thyristors can block voltage in both directions it is possible to

reverse the polarity of the output dc voltage and hence feed power back to the ac supply from the

dc side. Under such condition the converter is said to be operating in the “inverting mode”.

PROCEDURE:


7. Connect the DC shunt motor at the load terminals.




angle knob.

OBSERVATION TABLE:

S.No.

S. No.

Voltage

(V)

Motor Speed

rpm

1

2


RESULT:

Thus we have performed the speed control operation of DC shunt motor by using full controlled

converter.

PRECAUTIONS:





VIVA QUIZ:

1. How many SCRs are used in 3-phase full controlled bridge converter?


3. What are filter?

4. Why is it necessary to give excitation to field before giving supply to armature in a separately

excited motor?

5. Which method of speed control provides constant torque derive?

6. Can a D.C. starter be used for speed control?

7. What is the difference between speed control and speed regulation of a motor?

8. Explain why the speed changes with load?

9. Which method of speed control provides constant horse power derive?

10. In the armature voltage control method, Is the graph for armature voltage Vs. speed linear?

11. Which type of bridge converter is more efficient?

12. Why should we use full controlled converter while we have half controlled converter?

13. Which type motor has good controlling of speed?

14. Where this method is is applicable?

15. Which method should be used for controlling of compound motor?

3

4


------------------------

EXPERIMENT # 8

OBJECT: Speed control of a 3-phase induction motor in variable stator voltage mode using 3-

phase AC voltage regulator.

APPARATUS REQUIRED:


1 Induction Motor

control kit 415V, 3Amp, 50Hz 1


requirement



5 Induction Motor Slip Ring 415V, 1440rpm, 3HP 1


THEORY:

We can see that the torque depends on the square of the applied voltage. The variation of speed

torque curves with respect to the applied voltage is shown in fig. 27. These curves show that the

slip at maximum torque ˆs remains same, while the value of stall torque comes down with

decrease in applied voltage. The speed range for stable operation remains the same.

Further, we also note that the starting torque is also lower at lower voltages. Thus, even if

a given voltage level is sufficient for achieving the running torque, the machine may not start.

This method of trying to control the speed is best suited for loads that require very little starting

torque, but their torque requirement may increase with speed. Curve also shows a load torque


characteristic — one that is typical of a fan type of load. In a fan (blower) type of load, the

variation of torque with speed is such that T / !2.

Here one can see that it may be possible to run the motor to lower speeds within the range ns to

(1 − ˆs)ns. Further, since the load torque at zero speed is zero, the machine can start even at

reduced voltages. This will not be possible with constant torque type of loads. One may note that

if the applied voltage is reduced, the voltage across the magnetizing branch also comes down.

This in turn means that the magnetizing current and hence flux level are reduced. Reduction in

the flux level in the machine impairs torque production


Circuit Diagram

PROCEDURE:


2. Connect the 3-phase Induction motor at the load terminals.





angle knob.

OBSERVATION TABLE:

RESULT:

Thus we have performed the speed control operation of Induction motor by using AC voltage

regulator.

PRECAUTIONS:





VIVA QUIZ

1. How does the speed of induction motor depend on stator voltage?



4. How does the voltage regulator connected with induction motor?

S.No.

S. No.

Voltage

(V)

Motor Speed

rpm

1

2

3

4


5. Give the formula for speed of induction motor?

6. Which parameter other than voltage is responsible for speed variation of IM?

7. What is working principle of Induction motor?

8. How many circuit configurations available for AC voltage regulator?

9. What are the methods of speed control of induction machine?

10. Which factor affects the speed of induction motor most?

11. How many types of induction machine are available?


13. What type of output is obtained by AC voltage regulator?

14. Is there harmonics problem present in output of AC voltage regulator?


16. Which type of induction motor is controlled by AC voltage regulator?


EXPERIMENT # 9

OBJECT: Control the speed of Universal motor using AC voltage regulator. APPARATUS REQUIRED:


1 Universal Motor

control kit 415V, 3Amp, 50Hz 1


requirement



5 Motor Universal 1


THEORY:

An electric motor is an electromechanical device that converts electrical

energy into mechanical energy. Most electric motors operate through the interaction of magnetic

fields and current-carrying conductors to generate force. The reverse process, producing

electrical energy from mechanical energy, is done by generators such as an alternator or

a dynamo; some electric motors can also be used as generators, for example, a traction motor on

a vehicle may perform both tasks. Electric motors and generators are commonly referred to

as electric machines.

Universal AC Motors:

Universal ac motors operate with nearly equivalent performance on direct current or alternating

current up to 60 Hz. AC motors differ from a dc motors due to the winding ratios and thinner

iron laminations. DC motors runs on ac, but with poor efficiency. Universal ac motors can

operate on dc with essentially equivalent ac motor performance, but with poorer commutation

and brush life than for an equivalent dc motor.

An important characteristic of universal ac motors is that it has the highest horsepower-per-

pound ratio of any ac motor because it can operate at speeds many times higher than that of any

other 60-Hz electric motor. When operated without load, universal ac motors tend to run away,

speed being limited only by windage, friction, and commutation. Therefore, large universal ac

motors are nearly always connected directly to a load to limit speed. On portable tools such as

http://en.wikipedia.org/wiki/Electromechanics

http://en.wikipedia.org/wiki/Electrical_energy

http://en.wikipedia.org/wiki/Electrical_energy

http://en.wikipedia.org/wiki/Mechanical_energy

http://en.wikipedia.org/wiki/Motor

http://en.wikipedia.org/wiki/Magnetic_fields

http://en.wikipedia.org/wiki/Magnetic_fields

http://en.wikipedia.org/wiki/Electrical_conductor

http://en.wikipedia.org/wiki/Electrical_generator

http://en.wikipedia.org/wiki/Alternator

http://en.wikipedia.org/wiki/Dynamo

http://en.wikipedia.org/wiki/Traction_motor

http://en.wikipedia.org/wiki/Electric_machine


electric saws, the load imposed by the gears, bearings, and cooling fan is sufficient to hold the

no-load speed down to a safe value.

With a universal ac motor, speed control is simple, since electric motor speed is sensitive to both

voltage and flux changes. With a rheostat or adjustable autotransformer, ac motor speed can be

readily varied from top speed to zero

Ac voltage Regulator:-

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage

regulator may be a simple "feed-forward" design or may include negative feedback control

loops. It may use an electromechanical mechanism, or electronic components. Depending on the

design, it may be used to regulate one or more AC or DC voltages.

Electronic voltage regulators are found in devices such as computer power supplies where they

stabilize the DC voltages used by the processor and other elements. In automobile alternators and

central power station generator plants, voltage regulators control the output of the plant. In

an electric power distribution system, voltage regulators may be installed at a substation or along

distribution lines so that all customers receive steady voltage independent of how much power is

drawn from the line.

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Negative_feedback

http://en.wikipedia.org/wiki/Control_theory

http://en.wikipedia.org/wiki/Control_theory

http://en.wikipedia.org/wiki/Mechanism_(technology)

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Alternator

http://en.wikipedia.org/wiki/Power_station

http://en.wikipedia.org/wiki/Electric_power_distribution


PROCEDURE:


2. Connect the Universal motor at the load terminals.




angle knob.

OBSERVATION TABLE:

RESULT:

Thus we have performed the speed control operation of universal motor by using AC voltage

regulator.

PRECAUTIONS:





S.No.

S. No.

Voltage

(V)

Motor Speed

Rpm

1

2

3

4

5


VIVA QUIZ:

1. What is working principle of universal motor?


3. Give the formula for speed of universal motor?

4. How does the voltage regulator connected with universal motor?

5. How does the speed of universal motor depend on voltage?

6. Which parameter other than voltage is responsible for speed variation of universal?



9. What are the methods of speed control of universal machine?

10. Which factor affects the speed of universal motor most?

11. Here we use single phase regulator or three phase regulator?

12. Universal motor works on AC supply or DC supply system?

13. Can we use frequency control method to control speed of universal motor?

14. What should we do to change the direction of rotation of universal motor?


------------------------------------


EXPERIMENT # 10

OBJECT: Study of 3-phase dual converter.

THEORY:

Dual Converter is an Electronic Device or Circuit made by the combination of two bridges. One

of them works as Rectifier (Converts A.C. to D.C.) and other bridge works as Inverter (converts

D.C. into A.C.). Thus an electronic circuit or device, in which two processes take place at same

time, is known as Dual Converter. A dual converter may be single phase or 3 phase device. The simple diagram given above

is of single phase dual converter.

The difference between single phase and three phase dual converter is just that in Three

phase we uses three phase rectifier at first stage, while in single phase dual converter we make

use of single phase rectifier circuit at first bridge.

Single Phase Dual Converter:

As explained above that in single phase dual converter we uses single phase rectifier circuit for

converting single phase A.C. into steady D.C. Bridge No. 1 consists of Rectifier. Then the

rectified D.C. fed to a filter which removes pulses from rectified D.C. and converts it to a pure

D.C. by filtering. After that, this pure D.C. is fed to load and from load it is given to inverter

circuit which converts this D.C. to A.C. and finally this A.C. of inverter taken as output.

Three Phase Dual Converter: In three phase dual converter, we make use of three phase rectifier which converts 3 phase A.C.

supply to D.C. The rest of the process is same and same elements are used. The output of three

phase rectifier is fed to filter and after filtering the pure D.C. is fed to load. At last the supply

from load is given to last bridge that is inverter. It does the Invert process of rectifier and

converts D.C. into 3 phases A.C. which appears at output.

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Output wave form of three phase dual converter

Applications of Dual Converter: Dual converters are mostly used at industries where we require reversible D.C. Generally

Dual Converters are used for Speed Control of D.C. Motors etc.

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RESULTS: Thus we have studied the working operation, output and applications of three phase

dual converter

VIVA QUIZ:

1. What do you mean by dual converter?

2. Why we use dual converter?

3. How does a dual converter works?

4. Can we use the dual converter as an inverter?

5. What are the fields of its application?

6. What is the working principle of dual convertor?

7. Does we have single phase dual converter?

8. How many circuit configurations available for dual converter?

9. How does it work as rectifier and inverter both?

10. Can we use dual convertor in DC system?

11. What is the difference between circuit configuration of single phase and three phase dual

converter?

12. What type of output is obtained by three phase dual converter?

13. Can we have single phase dual converter?

14. Which type of dual converter is best?

15. What is the use of firing circuit in dual converter?

16. What is effect of firing in operation of dual converter?

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EXPERIMENT # 11

OBJECT: Study speed control of DC motor using 3-phase dual converter.

THEORY:



flux control method




inexpensive




Advantages





Disadvantages





Note. The field of a shunt motor in operation should never be opened because its

speed will increase to an extremely high value.






Disadvantages

(i) A large amount of power is wasted in the controller resistance since it Carries full armature

current Ia.










Dual Converter is an Electronic Device or Circuit made by the combination of two bridges. One

of them works as Rectifier (Converts A.C. to D.C.) and other bridge works as Inverter (converts

D.C. into A.C.). Thus an electronic circuit or device, in which two processes take place at same

time, is known as Dual Converter. A dual converter may be single phase or 3 phase device. The simple diagram given above

is of single phase dual converter.

The difference between single phase and three phase dual converter is just that in Three

phase we uses three phase rectifier at first stage, while in single phase dual converter we make

use of single phase rectifier circuit at first bridge.

Three Phase Dual Converter: In three phase dual converter, we make use of three phase rectifier which converts 3 phase A.C.

supply to D.C. The rest of the process is same and same elements are used. The output of three

phase rectifier is fed to filter and after filtering the pure D.C. is fed to load. At last the supply

from load is given to last bridge that is inverter. It does the Invert process of rectifier and

converts D.C. into 3 phases A.C. which appears at output.

Speed control of DC motor using 3 phase Dual converter

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RESULT:

Thus we have performed the speed control operation of DC shunt motor by using three phase

Dual converter.

VIVA QUIZ:

1. How does a dual converter applicable in speed control of dc motor?

2. Why should we use dual converter in speed control of a motor?

3. What are the methods of speed control of DC motor?

4. Can we use the dual converter as an inverter?

5. How a dual converter does is applicable in speed control of motor in inverting mode?

6. What is the working principle of dual convertor?

7. Can we use single phase dual converter in speed control of motor?

8. What do you mean by dual converter?

9. How does it work as rectifier and inverter both?

10. Can we use dual convertor in DC system?

11. What are the important conditions in speed control of dc motor?

12. Which parameter is varied in speed control of dc motor?

13. Why should we three phase dual converter instead of single phase converter?

14. Does a dual can control the speed of motor in both directions?

15. What parameters are used to control the speed of a dc motor?


EXPERIMENT # 12

OBJECT: To study cycloconverter and speed control of synchronous motor using

cycloconverter.

THEORY:

In industrial applications, two forms of electrical energy are used: direct current (dc)

and alternating current (ac). Usually constant voltage constant frequency single-phase or three-

phase ac is readily available. However, for different applications, different forms, magnitudes

and/or frequencies are required. There are four different conversions between dc and ac power

sources. These conversions are done by circuits called power converters. The converters are

classified as:

1-rectifiers: from single-phase or three-phase ac to variable voltage

dc 2-choppers: from dc to variable voltage dc

3-inverters: from dc to variable magnitude and variable frequency, single-phase or three-

phase ac

4-cycloconverters: from single-phase or three-phase ac to variable magnitude and

variable frequency, single-phase or three-phase ac The first three classes are explained in other articles. This article explains what cycloconverters

are, their types, how they operate and their applications.

Traditionally, ac-ac conversion using semiconductor switches is done in two different ways: 1- in

two stages (ac-dc and then dc-ac) as in dc link converters or 2- in one stage (ac-ac)

cycloconverters (Fig. 1). Cycloconverters are used in high power applications driving induction

and synchronous motors. They are usually phase-controlled and they traditionally use thyristors

due to their ease of phase commutation.

AIETM/ Department of Electrical

Engineering/EDTC Lab pg.-66


There are other newer forms of cycloconversion such as ac-ac matrix converters and high

frequency ac-ac (hfac-ac) converters and these use self-controlled switches. These converters,

however, are not popular yet.

Some applications of cycloconverters are:

Cement mill drives

Ship propulsion drives

Rolling mill drives

Scherbius drives

Ore grinding mills

Mine winders

1. Operation Principles: The following sections will describe the operation principles of the cycloconverter starting from

the simplest one, single-phase to single-phase (1-1) cycloconverter.

1.1. Single-phase to Single-phase (1-1) Cycloconverter: To understand the operation principles of cycloconverters, the single-phase to single-phase

cycloconverter (Fig. 2) should be studied first. This converter consists of back-to-back

connection of two full-wave rectifier circuits. Fig 3 shows the operating waveforms for this

converter with a resistive load.

The input voltage, vs is an ac voltage at a frequency, fi as shown in Fig. 3a. For easy

understanding assume that all the thyristors are fired at =0 firing angle, i.e. thyristors act like

diodes. Note that the firing angles are named as P for the positive converter and N for the

negative converter.


Consider the operation of the cycloconverter to get one-fourth of the input frequency at

the output. For the first two cycles of vs, the positive converter operates supplying current to the

load. It rectifies the input voltage; therefore, the load sees 4 positive half cycles as seen. In the

next two cycles, the negative converter operates supplying current to the load in the reverse

direction. The current waveforms are not shown in the figures because the resistive load

Current will have the same waveform as the voltage but only scaled by the resistance. Note that

when one of the converters operates the other one is disabled, so that there is no current

circulating between the two rectifiers.

Single-phase to single-phase cycloconverter


Single-phase to single-phase cycloconverter waveforms

a) input voltage b) output voltage for zero firing angle

c) output voltage with firing angle /3 rad. d) output voltage with varying firing angle

Three-Phase to Three-Phase (3-3) Cycloconverter: If the outputs of 3 3-1 converters of the same kind are connected in wye or delta and if the output

voltages are 2/3 radians phase shifted from each other, the resulting converter is a three-phase to

three-phase (3-3) cycloconverter. The resulting cycloconverters are shown in Figs. 7 and 8 with wye

connections. If the three converters connected are half-wave converters, then the new converter is

called a 3-3 half-wave cycloconverter. If instead, bridge converters are used, then the result is a 3-

3 bridge cycloconverter. 3-3 half-wave cycloconverter is also called a 3-pulse cycloconverter or an

18-thyristor cycloconverter. On the other hand, the 3-3 bridge cycloconverter is also called a 6-

pulse cycloconverter or a 36-thyristor cycloconverter. The operation of each phase is explained in the

previous section.

3-3 half-wave cycloconverter


3-3 bridge cycloconverter

The three-phase cycloconverters are mainly used in ac machine drive systems running three-

phase synchronous and induction machines. They are more advantageous when used with a

synchronous machine due to their output power factor characteristics. A cycloconverter can supply

lagging, leading, or unity power factor loads while its input is always lagging. A synchronous

machine can draw any power factor current from the converter. This characteristic operation

matches the cycloconverter to the synchronous machine. On the other hand, induction machines can

only draw lagging current, so the cycloconverter does not have an edge compared to the other

converters in this aspect for running an induction machine. However, cycloconverter are used in

Scherbius drives for speed control purposes driving wound rotor induction motors.

RESULTS: Thus we have studied about the cycloconverter and its use in speed control operation

of cycloconverter.


VIVA QUIZ:

1. What is the function of a cycloconverter?

2. What is the basic working principle of cycloconverter?

3. A cycloconverter works on AC or DC supply?

4. Is the frequency change in output of cycloconverter?

5. How does the frequency change in output of cycloconverter?

6. What is difference between a single phase and a three phase cycloconverter?

7. How does it used for speed control of synchronous motor?

8. What other methods are available for speed control of synchronous motor?

9. What are the other applications of three phase cycloconverter?

10. What is the speed formula of synchronous motor?

11. How does the speed of a synchronous motor depend on frequency?

12. How many types of synchronous motor are there?

13. Which type of synchronous motor is controlled by cycloconverter?

14. How does a synchronous motor connected with a cycloconverter?

15. Cycloconverter feeds the synchronous motor at stator or rotor?

16. Which type of supply is given to the rotor of a synchronous motor?

---------------------------

AIET/ Department of Electrical Engineering/EDTC Lab/72

EXPERIMENT # 13

OBJECT: To study the speed control of 3-phase Induction motor in variable frequency V/f

constant mode using 3-phase inverter.

THEORY:

Induction Machines, the most widely used motor in industry, have been traditionally

used in open-loop control applications, for reasons of cost, size, reliability, ruggedness,

simplicity, efficiency, less maintenance, ease of manufacture and its ability to operate in dirty or

explosive conditions. However, because the induction machine requires more complex control

methods, the dc machine has predominated in high performance applications. With

developments in Micro-processors/DSPs, power electronics and control theory, the induction

machine can now be used in high performance variable-speed applications.

The induction motor speed variation can be easily achieved for a short range by either

stator voltage control or rotor resistance control. But both of these schemes result in very low

efficiencies at lower speeds. The most efficient scheme for speed control of induction motor is

by varying supply frequency. This not only results in scheme with wide speed range but also

improves the starting performance.

If the machine is operating at speed below base speed, then v/f ratio is to be kept constant

so that flux remains constant. This retains the torque capability of the machine at the same value.

But at lower frequencies, the torque capability decrease and this drop in torque has to be

compensated for increasing the applied voltage.


Speed Torque Characteristics of Induction Motor with frequency variation

The above curve suggests that the speed control and braking operation are available from

nearly zero speed to above synchronous speed. It is noted that V is kept constant above base

speed and freq. is increasing. The variable frequency control provides good running and transient

performance because of the following features:

voltage and frequency variation in VSI fed Induction motor

(a) Speed control and braking operation are possible from zero to above base speed.

(b) During transients (starting, braking and speed reversal), the operation can be carried out at

the maximum torque with reduced current giving good dynamic response.

(c) Copper losses are reduced, efficiency and power factor are high as the operation is in between

synch. speed and max. torque point at all frequencies.

(d) Drop in speed from no load to full load is small.

Above fig shows the block diagram of a V/f control of VSI fed three phase induction

motor drive. In this according to the reference speed input command (N r*) the reference

frequency (f*) and reference voltage (V*) commands are calculated such that V/f ratio maintained

to be constant. The reference commands V* and f* are given to the SPWM generator to generate

6-PWM pulses to the three-phase voltage source inverter which drives the three-phase induction

motor.


Block Diagram Schematic of V/f control of VSI fed 3-phase Induction Motor drive

Modes of operation and variation of is, ωsl,, T and Pm with per unit frequency K .

RESULT:


Thus we have studied the speed control operation of Induction motor in variable frequency mode

using 3-phase inverter.

VIVA QUIZ:

1. How does the speed of induction motor depend on stator voltage?

2. Which factor affects the speed of induction motor most?

3. Which parameter other than voltage is responsible for speed variation of IM?

4. Why should we keep v/f ratio constant?

5. Give the formula for speed of induction motor?

6. How does the speed of induction motor depend on frequency?

7. What is working principle of Induction motor?

8. What do you mean flux density?

9. What are the methods of speed control of induction machine?

10. How an inverter does is used in speed control?

11. How many types of induction machine are available?

12. Which type of induction motor is controlled by varying the frequency?

13. Can we use separate supply system for rotor?

14. Is there harmonics problem present in output of inverters?

15. In which mode the IM works for higher frequency reduction?

16. What do you mean by slip speed of an induction motor?

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LAB-MANUAL · AIETM/ Department of Electrical Engineering/EDTC Lab pg.-2 14. Exp-9 Control speed of...

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