2009 Anna University Chennai B.E Electrical and Electronics Engineering EE 2253 control system Question paper

ANNA UNIVERSITY COIMBATORE
B.E/B.TECH. DEGREE EXAMINATIONS: MAY/JUNE 2010
REGULATIONS: 2008
FOURTH SEMESTER
080280033-CONTROL SYSTEMS
(COMMON TO EEE/EIE/ICE)

TIME: 3 Hours Max.Marks:100
PART-A
(20*2=40 MARKS)
ANSWER ALL QUESTIONS

1. Distinguish between open loop and closed loop system.
2. What is the effect of positive feedback on stability?
3. What is synchro pair?
4. Write the transfer function of PI, PD and PID controllers.
5. Define damping ratio.
6. The closed loop transfer function of a second order system is given by 200/s2+20s+200.
Determine the damping ratio and natural frequency of oscillation.
7. Define settling time.
8. The damping ratio of a system is 0.75 and the natural frequency of oscillation is
12 rad/sec. determine the peak overshoot and the peak time.
9. Define gain margin.
10. Define corner frequency.
11. Give the significance of polar plot in finding frequency response.
12. Define minimum and non minimum phase system.
13. What will be the nature of impulse response if the roots of characteristic equation are
lying on right half s-plane?
14. What is breakaway and break in point? How to determine them?
15. How will you find root locus on real axis?
16. What are asymptotes? How will you find the angle of asymptotes?
17. The damping ratio of system is 0.6 and natural frequency of oscillation is 8 rad/sec.
Determine the rise time.
18. Write transfer function of lag-lead compensator.
19. Compare series compensator and feedback compensator

20. Draw electrical lag-lead compensator network.
PART-B
(5*12=60 marks)
ANSWER ANY FIVE QUESTIONS
21. Using block diagram reduction technique find the closed loop transfer function of the
system whose block diagram is shown below. (12)
22. Derive the expressions for rise time, peak time and peak overshoot.
23. Sketch the bode plot and hence find gain cross over frequency, phase cross over frequency,
gain margin and phase margin(s) =0.75(1+0.2s)/s(1+0.5s)(1+0.1s) (12)
24. The characteristic polynomial system is S7 + 9S6 + 24S5 + 24S4 + 24S3 + 24S2 + 23S +
15=0. Determine the location of roots on s-plane and hence the stability of the system. (12)
25. Explain the procedure for finding the transfer function of lead compensation and lag
Compensation. (12)
26. Find the overall gain of the system whose signal flow graph is shown in figure below. (12)
27. The open loop transfer function of a servo system with unity feedback system is
G(s) = 10/s (0.1s+1). Evaluate the static error constants of the system. Obtain the steady
State error of the system when subjected to an input given by the polynomial
r (t)=a0 + a1t + a2/2t2. (12)
28 (a). Derive the expressions and draw the response of first order system for unit step input. (6)
(b). Draw and explain the response of second order system for critically damped case and
When the input is unit step. (6)

2009 Anna University Chennai B.E Electrical and Electronics Engineering Ee2254 — linear integrated circuits and applications Question paper

B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010
Fourth Semester
Electrical and Electronics Engineering
EE2254 — LINEAR INTEGRATED CIRCUITS AND APPLICATIONS
(Regulation 2008)
(Common to Instrumentation and Control Engineering and Electronics and
Instrumentation Engineering)

Time: Three hours Maximum: 100 Marks


Answer ALL Questions
PART A — (10 ??2 = 20 Marks)
1. What is the purpose of oxidation process in IC fabrication?
2. What is parasitic capacitance?
3. List any four characteristics of an ideal OP-Amp.
4. Design an amplifier with a gain of –10 and input resistance of 10 k?.
5. Define slew rate and state its significance.
6. An 8 bit DAC has a resolution of 20mV/bit. What is the analog output voltage
for the digital input code 00010110 (the MSB is the left most bit)?
7. Draw the pin diagram of IC 555 timer.
8. Mention any two application of multiplier IC.
9. List the important parts of regulated power supply.
10. What are the advantages of switch mode power supplies?

PART B — (5 ??16 = 80 Marks)
11. (a) Explain the basic processes used in silicon planar technology with neat diagram.
Or
(b) Discuss the various methods used for fabricating IC resistors and compare their performance.

12. (a) (i) Explain the functions of all the basic building blocks of an Op-Amp.(8)
(ii) Explain the application of OPAMP as
(1) integrator
(2) differentiator. (8)
Or
13. (a) Design and explain triangular wave generator using Schmitt trigger and integrator circuit.
Or
(b) (i) Explain the operation of dual slope ADC. (8)
(ii) Explain the following characteristics of ADC resolution, accuracy,
settling time, linearity. (8)
14. (a) With neat block diagram, explain IC566 VCO operation and discuss any
two applications.
Or
(b) What are the modes of operation of IC555? Derive the expression of time delay of a monostable multivibrator.

15. (a) With a neat diagram, explain working principle of switch mode lower supply.
Or
(b) Write brief notes on:
(i) IC MA 78 40
(ii) Optocoupler.

2008 Anna University Chennai B.E -ELECTRICAL ENGINEERING - EE 1X11- Question paper

T 3914
B.E/B.Tech DEGREE EXAMINATIONS,APRIL/MAY 2008.
Annual Pattern –First Year
(REGULATIONS 2004)

EE 1X11-ELECTRICAL ENGINEERING
(Common to Information Technology)
Time:Three hours Maximum:100marks

Answer ALL questions.

PARTA-(10×2=20marks)
1. What is meant by electric energy?

2. What are the advantages of polyphase system?

3. State Faraday’s law of electromagnetic induction.

4. What is mutual inductance?

5. List out the different types of DC motor.

6. What are the advantages of three phase Transformer?

7. Define pitch factor.

8. Single phase induction motor is not self standing.Why?

9. Compare open loop and closed loop systems.

10. Define Rise time(tr).

PARTB-(5×16=80marks)

11. (a) Use super position theorem to find a current through 20O resistance.

Or

(b) In a series RLC circuit R=24 O, L=191 mH, C=100 µF given that the supply voltage is 240 V, 60 Hz, Find (i) Equivalent impedance
(ii) Power factor
(iii) Current (iv) Power
(v) Reactive power.

12. (a) Write short notes on:
(i) Parallel Magnetic Circuits.
(ii)AC operation of Magnetic Circuits.

Or

(b) (i) Explain the terms self and mutual inductances.
(ii) A coil has a self-inductance of 30 mH. Calculate the EMF induced in the coil(1) increases at a rate of 300 A/sec. (2) Raises from 0 to 10 A in 0.06 seconds.

13. (a) Derive the equivalent circuit of a Single-phase transformer and show how it is useful in the analysis of the performance of a transformer.

Or

(b) Discuss the function and constructional details of the following parts of DC machine (i) Commutator (ii) Brus assembly and (iii) Interpoles.

14. (a) Explain various methods of starting of three phase induction motor.

Or

(b) Describe various methods of starting of single-phase induction motor with industrial applicaion.

15. (a) Explain the working principle of a 2-Phase AC servomotor. Derive its transfier function.

OR
(b) Derive the transfer function of a separately excited DC generator at no load condition.

History of electrical engineering

Ancient developments

Thales of Miletus, an ancient Greek philosopher, writing at around 600 BCE, described a form of static electricity, noting that rubbing fur on various substances, such as amber, would cause a particular attraction between the two. He noted that the amber buttons could attract light objects such as hair and that if they rubbed the amber for long enough they could even get a spark to jump.At around 450 B.C. Democritus, a later Greek philosopher, developed an atomic theory that was remarkably similar to our modern atomic theory. His mentor, Leucippus, is credited with this same theory. The hypothesis of Leucippus and Democritus held everything to be composed of atoms. But these atoms, called "atomos", were indivisible, and indestructible. He presciently stated that between atoms lies empty space, and that atoms are constantly in motion. He was incorrect only in stating that atoms come different sizes and shapes. Each object had its own shaped and sized atom.

19th century developments

In the 19th century, the subject of electrical engineering, with the tools of modern research techniques, started to intensify. Notable developments in this century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, Michael Faraday, the discoverer of electromagnetic induction in 1831, and James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise on Electricity and Magnetism. In the 1830s, Georg Ohm also constructed an early electrostatic machine. The homopolar generator was developed first by Michael Faraday during his memorable experiments in 1831. It was the beginning of modern dynamos — that is, electrical generators which operate using a magnetic field. The invention of the industrial generator, which didn't need external magnetic power in 1866 by Werner von Siemens made a large series of other inventions in the wake possible. In 1878, the British inventor James Wimshurst developed an apparatus that had two glass disks mounted on two shafts (ed. it was not till 1883 that the Wimshurst machine was more fully reported to the scientific community).

During the latter part of the 1800s, the study of electricity was largely considered to be a subfield of physics. It was not until the late 19th century that universities started to offer degrees in electrical engineering. In 1882, Darmstadt University of Technology founded the first chair and the first faculty of electrical engineering worldwide. In the same year, under Professor Charles Cross, at the Massachusetts Institute of Technology began offering the first option of Electrical Engineering within a physics department.In 1883, Darmstadt University of Technology and Cornell University introduced the world's first courses of study in electrical engineering and in 1885 the University College London founded the first chair of electrical engineering in the United Kingdom. The University of Missouri subsequently established the first department of electrical engineering in the United States in 1886.

During this period work in the area increased dramatically. In 1882 Edison switched on the world's first large-scale electrical supply network that provided 110 volts direct current to fifty-nine customers in lower Manhattan. In 1887 Nikola Tesla filed a number of patents related to a competing form of power distribution known as alternating current. In the following years a bitter rivalry between Tesla and Edison, known as the "War of Currents", took place over the preferred method of distribution. AC eventually replaced DC for generation and power distribution, enormously extending the range and improving the safety and efficiency of power distribution.

The efforts of the two did much to further electrical engineering—Tesla's work on induction motors and polyphase systems influenced the field for years to come, while Edison's work on telegraphy and his development of the stock ticker proved lucrative for his company, which ultimately became General Electric.

However, by the end of the 19th century, other key figures in the progress of electrical engineering were beginning to emerge. Charles Proteus Steinmetz helped foster the development of alternating current that made possible the expansion of the electric power industry in the United States, formulating mathematical theories for engineers.

Modern developments

Emergence of radio and electronics

Beginning of the 20th century

During the development of radio, many scientists and inventors contributed to radio technology and electronics. In his classic UHF experiments of 1888, Heinrich Hertz transmitted (via a spark-gap transmitter) and detected radio waves using electrical equipment. In 1895 Guglielmo Marconi was the first scientist to achieve radio transmission (2.4 km), around the same time Nikola Tesla was able to detect signals from the transmissions of his New York lab at West Point (a distance of 80.4 km). In 1896, Alexander Popov made wireless transmissions across 60 m. John Fleming invented the first radio tube, the diode, in 1904.

Reginald Fessenden recognized that a continuous wave needed to be generated to make speech transmission possible, and he continued the work of Nikola Tesla, John Stone Stone, and Elihu Thomson on this subject. By the end of 1906, Fessenden sent the first radio broadcast of voice. Also in 1906, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode. Edwin Howard Armstrong enabling technology for electronic television, in 1931.

Second World War years

The second world war saw tremendous advances in the field of electronics; especially in RADAR and with the invention of the magnetron by Randall and Boot at the University of Birmingham in 1940. Radio location, radio communication and radio guidance of aircraft were all developed in Britain at this time. An early electronic computing device, Colossus was built by Tommy Flowers of the GPO to decipher the coded messages of the German Lorenz cipher machine. Also developed at this time were advanced clandestine radio transmitters and receivers for use by secret agents. An American invention at the time was a device to scramble the telephone calls between Churchill and Roosevelt. This was called the Green Hornet system and worked by inserting noise into the signal. The noise was then extracted at the receiving end. This system was never broken by the Germans. A great amount of work was undertaken in the United States as part of the War Training Program in the areas of radio direction finding, pulsed linear networks, frequency modulation, vacuum tube circuits, transmission line theory and fundamentals of electromagnetic engineering. These studies were published shortly after the war in what became known as the 'Radio Communication Series' published by McGraw hill 1946. In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer.

Post war developments

Prior to the second world war the subject was commonly known as 'radio engineering' and basically was restricted to aspects of communications and RADAR, commercial radio and early television. At this time, study of radio engineering at universities could only be undertaken as part of a physics degree.

Later, in post war years, as consumer devices began to be developed, the field broadened to include modern TV, audio systems, Hi-Fi and latterly computers and microprocessors. In 1946 the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo missions and the NASA moon landing.

The invention of the transistor in 1947 by William B. Shockley, John Bardeen and Walter Brattain opened the door for more compact devices and led to the development of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronics engineering, which then became a stand alone university degree subject, usually taught alongside electrical engineering with which it had become associated due to some similarities. In 1968 Marcian Hoff invented the first microprocessor at Intel and thus ignited the development of the personal computer. The first realization of the microprocessor was the Intel 4004, a 4-bit processor developed in 1971, but only in 1973 did the Intel 8080, an 8-bit processor, make the building of the first personal computer, the Altair 8800, possible.

An object found in Iraq in 1938, dated to about 250 BCE and called the Baghdad Battery, resembles a galvanic cell and is believed by some to have been used for electroplating in Mesopotamia, although this has not yet been proven.

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TESTING OF ELECTRICAL MACHINES USING A DATA ACQUISITION AND PROCESSING SYSTEM

Abstract –

The paper deals with electrical machines testing , including high power ones, using an Data Acquisition and Processing System (DAPS), based on a PC compatible microsystem. There are presented the architecture and the main measurement possibilities of DAPS in electrical

machines testing, in various functional conditions: constant frequency steady state (used in classical standard tests), variable frequency conditions (used in asynchronous motors testing by mixed frequency method) and finally, transient conditions. For every testing condition, there are considered measured quantities, their processing methods, and are illustrated with some practical examples, developed by authors.

INTRODUCTION

In the electrical machine design, the accuracy of the calculated values of the parameters and characteristics is limited by the saturation effect of magnetic coils, the skin current effect and various technological causes. In some circumstances, not all of the initial data are known at the designing time. There are specific situations when the parameters and characteristics of electrical machines can be determined fast and accurate only by These results are necessary to determining the performance of those electric machines, to modelling them and toexperimental me ans [1]. improving the design method. Modern testing methods (variable frequency testing, variable active power in transient regime, frequency response) are efficient but they cannot be accomplished with classic measuring apparatuses. Specialized measuring equipment is required to perform such tests on an industrial testing platform . To answer the above requirements,

an electric mac hine testing unit (DAPS) was devised by designing a data acquisition board and a specialized software package, both mounted on a PC compatible machine.

THE HARDWARE ARCHITECTURE

The Data Acquisition and Processing System (DAPS) was conceived for testing electric machines in a wide range of operating conditions. The block diagram of the Data Acquisition and Processing System (DAPS) is presented in Figure

1. The DAPS consists of three major parts: the Transducer and Analog Signal Adapter (TASA), the Data Acquisition Module (DAM) and a PC-microcomputer. The hardware structure and tasks of the TASA and DAM are given in [2, 3, 4], while a general description of the TAS

A is shown in Figure 1. This module translates the analog signals acquired from the Electrical Machine (EM) to standard values [-10V ¸ +10V] compatible with the DAM inputs. The TASA module has been devised such as the DAPS can be used to perform tests on electrical machines operating in a various functional regimes.

The latest version of TASA is provided with voltage and current galvanic insulated transducers, which assure a sufficient precision for all the input channels.

The TASA has the following inputs:

· four voltage inputs with various measurement domains between 110 V and 660 V (regularly being used for measuring the ME supply voltages);

· four current inputs for measuring currents between 5 A and 10 A

(regularly being used to measure the ME supply currents);

· four small voltage inputs, to acquire signals in a 10 V range from magnetic field transducers or rotation transducers;

· two large current inputs (500 A –1500 A) used to studying the field currents in transient conditions of synchronous machine. Since the DAM has 8 differential inputs,not all the TASA channels can be used at a time.

A circuit for the testing of the synchronous machine is given in Fig. 1.

The following entities are measured: 3 stator voltages, 3 stator currents, the rotation transducer signal and the rotor field current. Current and voltage measure transformers are interposed between the tested machine and TASA if the voltages on the three phase stator windings are higher then the upper limit of TASA inputs.

DAPS OPERATING MODES

The DAPS is provided with three data acquisition and primary processing software programs to be used specifically for the following operating modes: steady state periodical conditions, slowly dumped periodical conditions and transient aperiodical condition. Based on these programs for data acquisition and primal processing, further software was developed in a modular structure.

A. Steady-state periodic conditions at rated frequency.

This is the most common regime used in electric machine testing. The DAPS acquires blocks of momentary values of current and voltage on each phase of the tested machine. Consecutive series of measurements are started manually by the human operator, each time the supply voltage is set up to a prescribed value (conform to the test program) and it reaches steady -state periodic conditions.Based on the momentary acquired values of voltage and current, i.e., v(t) and i(t), the DAPS calculates the following: the maximum values Vm, Im, the rms values Vrms, I rms, the phase angle j, the active power P, and the frequency f. In the case of harmonic conditions, the micro-system computes cosj and the reactive power, as well. If the waveform is not pure sinusoidal, then cosj and the reactive power are expressed relatively to the fundamental harmonic. All the above mentioned computations are conducted for each block of momentary values acquired from each phase and the results are accordingly synthesized in the measurement table. In this table, the Media raw contains, respectively, the averages of the currents, voltages, frequencies and cosj, but the sum of powers (active and reactive).The human operator may start a computer procedure to do the harmonic a nalysis of the acquired signals, as well.

B. Steady-state conditions at variable frequency .

The induction motor parameters are obtained as frequency functions by testing it in a short circuit mode at variable frequency. The data acquisition and processing are conducted similarly to the above regime, but the starting of each series of acquisition is accomplished in an automatic manner . Previously the test, the operator prescribes the frequencies at which the DAPS has to acquire each block of momentary values. While the frequency of the power supply is continuously decreased, the DAPS calculates in real time the current frequency to starting an acquisition process as a prescribed value is reached.Table 1 contains the results obtained by processing a block of acquired values in testing an induction machine at steady-state conditions at variable frequency. The acquired block is displayed in a graphical form by the DAPS for the required phase, as shown in Fig. 2.

Fig. 2. Display of a data acquisition block in steadystate short-circuit conditions of an induction machine.

C. Slowly dumped periodical conditions

In this regime, the data acquisition is continuously carried out in an automatic manner, as long as the acquired entities still present significant changes. The same values like in the above case are calculated, but rather continuously, for each half-period of the acquired signals. A no-load starting of an induction machine (0,63 kW, star connection, 380 V, 2900 rpm) is next presented. To increase the starting time, the supply voltage was reduced to 88 V, while the inertial constant J was increased by an additional inertial rotating part. Since the number of the lines in the measurement table is quite high, a few samples have been picked-up to illustrate the experiment as given in Table 2. There was added some more information in this measurement table: the second column represents the acquisition time and the third column in each block of values contains the value of the voltage signal from the rotation transducer.

Table 2. Samples of data acquired from an induction motor in a slow dumped no-load starting conditions

An other example of graphical versatility of DAPS, the active power used up by a 1,1 kW, 380 V, 920 rpm motor to start, and the speed as voltage signal are displayed in a graphical forms as a function of time in Fig. 3.

Based on the active power components, the torque curve M(n) of induction motors can be determined. This method plays an extremely important role in determining the torque curve for the very high power machines, for which the load test can not be carried out.

Fig. 4 represents the torque M as a function of slip (M expressed in per units,) completed in testing a 2800 kW/6000 V asynchronous motor at slow dumped conditions. The overall errors for currents and voltages are less than 0.2%, while they are smaller than 0.5% for the active power.

D. Mixed Frequency Conditions

These conditions are established every time an asynchronous machine is artificially loaded by

connecting to mixed frequency power supplies [5]. To carry out this test, the power supply of

the tested machine is built of a couple of synchronous generators connected in series and

having different frequencies (e.g., 44 Hz and 50Hz). DAPS is used to find out the effective

values of the supply currents and voltages in these specific conditions. Current and voltage as time function in a test of an induction machine with the mixed frequency method are presented in Fig. 5.