PART A — (10 ? 2 = 20 marks)
1. State the different parts of a dc generator and explain their functions.
2. Why do we need starters for dc motors?
3. Explain, why the Open Circuit test is generally performed at rated voltage on the LV side of a transformer.
4. Show that the maximum efficiency in a transformer occurs when its variable loss is equal to constant loss.
5. A 4 pole, 3 phase, synchronous motor run from a 50 H supply is mechanically coupled to a 24 pole synchronous generator. At what speed will the set rotate? What will be the frequency of the emf induced in the generator?
6. Why is a synchronous motor not self–starting?
7. If a 3-phase induction motor runs at 960 rpm on a 50 Hz supply, what is the number of poles in the motor?
8. Why can't an induction motor develop torque at synchronous speed?
9. Explain, how the starting winding assist to develop starting torque in single–phase induction motors.
10. How will you tell the direction of rotation of a shaded pole induction motor from its construction (without actually running the motor)?
PART B — (5 ? 16 = 80 marks)
11. Explain the principle of operation of a three–phase induction motor and draw its equivalent circuit. (8 + 8)
12. (a) (i) Draw and explain the load characteristics of a dc shunt generator. (8)
(ii) A 6 pole, wave wound 500 rpm, dc shunt generator has armature and field resistances of 0.5 ohm and 250 ohm respectively. The armature has 250 conductors and the flux per pole is 40 m Wb. If the load resistance is 15 ohm, determine the terminal voltage and load current. (8)
Or
(b) A 250 volts dc shunt motor takes an armature current of 20 amps and runs at 1000 rpm against full load torque. The armature resistance is 0.5 ohm. What resistance must be inserted in series with armature to reduce the speed to 500 rpm at the same load torque? With this resistance in circuit, determine the speed when the load torque reduced to 50%. Assume that the flux remains constant throughout. (16)
13. (a) Explain the constructional details and principle of operation of a single–phase transformer. (16)
Or
(b) A 4 kVA, 400/200 V, 50 Hz single phase transformer gave the following test results :
OC Test (LV side) : 60 Watts, 0.7 A, and 200 V
SC Test (HV side) : 21.6 Watts, 6 A, and 9 V
(i) Determine the equivalent circuit parameters of the transformer referred to LV side. (8)
(ii) Determine its voltage regulation at full load, 0.8 PF leading. (8)
14. (a) Derive the equation for the induced emf of a synchronous generator. (16)
Or
(b) Derive the expression for the torque developed by a synchronous motor and draw its torque angle characteristics. (16)
15. (a) Explain how torque is developed in a single phase induction motor according to the double revolving field theory. (16)
Or
(b) Draw a neat diagram of a universal motor and explain its operation. Also draw its torque–speed characteristics when it is operated with ac and dc sources and explain why they are different. (16)
Saturday, May 31, 2008
Anna univ IL 231 — CONTROL SYSTEMS
PART A — (10 ? 2 = 20 marks)
1. Define control system.
2. Define signal flow graph.
3. Give the uses of gyroscope.
4. What is a PID controller?
5. Give the step response of first order and second order system.
6. What is velocity error constant?
7. What is the type of the following system and why?
8. What are Bode plots?
9. What is CORNER frequency?
10. Using characteristic equation explain what is meant by stable system?
PART B — (5 ? 16 = 80 marks)
11. Determine the transfer function of the series RLC circuit given below.
12. (a) Find the Tr. fn of the mechanical system shown in fig. 1.
Or
(b) Find the transfer fn for the floating disc shown below.
K? stiffness coefficient of shaft.
13. (a) Using Mason’s gain formula determine the overall gain for the system shown below.
Or
(b) Reduce the no. of blocks into an equivalent one.
14. (a) For a second order system ? = 0.6 and W? = 5 rad/sec. Calculate rise time tr, peak time tp, maximum over shoot Mp, and settling time ts when the system is subjected to a unit step input.
Or
(b) For an unity feed back system haring an open loop transfer function.
Determine
(i) The type of the system
(ii) Kp, Kv, Ka
(iii) Steady state error for unit parabolic input.
15. (a) Find the range of K for the following system to be stable.
Or
(b) The open loop transfer function of a feedback control system is
Obtain the Nyquist plot and comment on the system stability.
1. Define control system.
2. Define signal flow graph.
3. Give the uses of gyroscope.
4. What is a PID controller?
5. Give the step response of first order and second order system.
6. What is velocity error constant?
7. What is the type of the following system and why?
8. What are Bode plots?
9. What is CORNER frequency?
10. Using characteristic equation explain what is meant by stable system?
PART B — (5 ? 16 = 80 marks)
11. Determine the transfer function of the series RLC circuit given below.
12. (a) Find the Tr. fn of the mechanical system shown in fig. 1.
Or
(b) Find the transfer fn for the floating disc shown below.
K? stiffness coefficient of shaft.
13. (a) Using Mason’s gain formula determine the overall gain for the system shown below.
Or
(b) Reduce the no. of blocks into an equivalent one.
14. (a) For a second order system ? = 0.6 and W? = 5 rad/sec. Calculate rise time tr, peak time tp, maximum over shoot Mp, and settling time ts when the system is subjected to a unit step input.
Or
(b) For an unity feed back system haring an open loop transfer function.
Determine
(i) The type of the system
(ii) Kp, Kv, Ka
(iii) Steady state error for unit parabolic input.
15. (a) Find the range of K for the following system to be stable.
Or
(b) The open loop transfer function of a feedback control system is
Obtain the Nyquist plot and comment on the system stability.
Anna univ EC 153 — ELECTRONIC DEVICES AND CIRCUITS
PART A — (10 ? 2 = 20 marks)
1. Define a hole. What is its importance?
2. The current flowing in a PN junction diode at room temperature is A, when a large reverse bias voltage is applied. Calculate the current flowing, when 0.1 V forward bias is applied at room temperature.
3. List the three sources of instability of collector current.
4. Define in words and also as a partial derivative
(a) (b) (c) (d)
5. What are the four possible topologies of a negative feedback amplifier?
6. Give the two Barkhausen conditions required for the sinusoidal oscillations to be sustained.
7. Draw the schematic block diagram of the basic op–amp with inverting and non inverting inputs and also draw the equivalent circuit.
8. Define :
(a) Power supply rejection ratio (b) Slew rate for an op–amp.
9. Sketch the idealized characteristics for the filter types
(a) Low pass (b) High pass (c) Band pass (d) Band reject filters.
10. List any four uses of Multivibrators.
PART B — (5 ? 16 = 80 marks)
11. (i) Draw the circuit diagram and output characteristics of a NPN transistor in CB configuration. Indicate the active, cutoff and saturation regions and explain the significance of the curve qualitatively. (10)
(ii) In the circuit shown below,
VCC = 24 V, RC = 10 k , RE = 270 . If a silicon transistor is used with = 45 and if VCE = 5 V, find R. Neglect the reverse saturation current.
(6)
12. (a) (i) In an open circuit PN junction, plot the space charge, electric field, electrostatic potential variation as a function of distance across the junction. (8)
(ii) Write the Volt–Ampere diode equation for a PN diode. With the help of this equation, explain the Volt–Ampere characteristics of a diode. (8)
Or
(b) (i) What are the requirements of a biasing circuit. (4)
(ii) Define stabilization technique and compensation technique. (4)
(iii) A CE amplifier with self bias arrangement as shown in figure employ an NPN transistor having = 99, and stability factor
S of 5. Calculate the values of R1, R2 and RE if the values of resistance RC and various voltages are as shown in figure. (8)
13. (a) (i) Draw the small signal equivalent circuit for CE transistor amplifier and deduce the expressions for current gain, input impedance, output impedance and voltage gain. (10)
(ii) A transistor used in a common base amplifier has the values of
h–Parameters Calculate the values of current gain, input resistance and voltage gain. Assume source resistance is zero. (6)
Or
(b) (i) Draw the block diagram of an amplifier with a feedback network and derive the expression for the voltage gain. (10)
(ii) Calculate the voltage gain, input and output resistances of a voltage series feedback amplifier having AV = 300, Ri = 1.5 k , Ro = 50 k and = 1/15. (6)
14. (a) (i) Differentiate oscillator with amplifier. (4)
(ii) Briefly explain how oscillators are classified. (4)
(iii) Draw the circuit diagram and explain the principle of operation Hartley oscillator. (8)
Or
(b) (i) List out the characteristics of ideal op–amp. (4)
(ii) Draw the circuit diagram of op–amp used in inverting amplifier and obtain the formula for voltage gain and VO. (4)
(iii) In fig. R1 = 10 k , Rf = 100 k , Vi = 1 V. A load of 25 k is connected to the output terminal. Calculate (1) I1 (2) V0 (3) IL and total current I0 in to the output pin. (8)
15. (a) (i) Draw the circuit of a Differentiator using op–amp and obtain the formula for output voltage and magnitude gain. (8)
(ii) Draw the circuit diagram with equation for V0 of an instrumentation amplifier and write down its important features and application. (8)
Or
(b) (i) Sketch the collector coupled astable multivibrator circuit. (4)
(ii) Determine period and frequency of oscillations for an astable multivibrator with components values R1 = 2 k , R2 = 20 k ,
C1 = 0.01 f, C2 = 0.05 f. (4)
(iii) Draw and explain the functional diagram of a 555 Timer. (8)
1. Define a hole. What is its importance?
2. The current flowing in a PN junction diode at room temperature is A, when a large reverse bias voltage is applied. Calculate the current flowing, when 0.1 V forward bias is applied at room temperature.
3. List the three sources of instability of collector current.
4. Define in words and also as a partial derivative
(a) (b) (c) (d)
5. What are the four possible topologies of a negative feedback amplifier?
6. Give the two Barkhausen conditions required for the sinusoidal oscillations to be sustained.
7. Draw the schematic block diagram of the basic op–amp with inverting and non inverting inputs and also draw the equivalent circuit.
8. Define :
(a) Power supply rejection ratio (b) Slew rate for an op–amp.
9. Sketch the idealized characteristics for the filter types
(a) Low pass (b) High pass (c) Band pass (d) Band reject filters.
10. List any four uses of Multivibrators.
PART B — (5 ? 16 = 80 marks)
11. (i) Draw the circuit diagram and output characteristics of a NPN transistor in CB configuration. Indicate the active, cutoff and saturation regions and explain the significance of the curve qualitatively. (10)
(ii) In the circuit shown below,
VCC = 24 V, RC = 10 k , RE = 270 . If a silicon transistor is used with = 45 and if VCE = 5 V, find R. Neglect the reverse saturation current.
(6)
12. (a) (i) In an open circuit PN junction, plot the space charge, electric field, electrostatic potential variation as a function of distance across the junction. (8)
(ii) Write the Volt–Ampere diode equation for a PN diode. With the help of this equation, explain the Volt–Ampere characteristics of a diode. (8)
Or
(b) (i) What are the requirements of a biasing circuit. (4)
(ii) Define stabilization technique and compensation technique. (4)
(iii) A CE amplifier with self bias arrangement as shown in figure employ an NPN transistor having = 99, and stability factor
S of 5. Calculate the values of R1, R2 and RE if the values of resistance RC and various voltages are as shown in figure. (8)
13. (a) (i) Draw the small signal equivalent circuit for CE transistor amplifier and deduce the expressions for current gain, input impedance, output impedance and voltage gain. (10)
(ii) A transistor used in a common base amplifier has the values of
h–Parameters Calculate the values of current gain, input resistance and voltage gain. Assume source resistance is zero. (6)
Or
(b) (i) Draw the block diagram of an amplifier with a feedback network and derive the expression for the voltage gain. (10)
(ii) Calculate the voltage gain, input and output resistances of a voltage series feedback amplifier having AV = 300, Ri = 1.5 k , Ro = 50 k and = 1/15. (6)
14. (a) (i) Differentiate oscillator with amplifier. (4)
(ii) Briefly explain how oscillators are classified. (4)
(iii) Draw the circuit diagram and explain the principle of operation Hartley oscillator. (8)
Or
(b) (i) List out the characteristics of ideal op–amp. (4)
(ii) Draw the circuit diagram of op–amp used in inverting amplifier and obtain the formula for voltage gain and VO. (4)
(iii) In fig. R1 = 10 k , Rf = 100 k , Vi = 1 V. A load of 25 k is connected to the output terminal. Calculate (1) I1 (2) V0 (3) IL and total current I0 in to the output pin. (8)
15. (a) (i) Draw the circuit of a Differentiator using op–amp and obtain the formula for output voltage and magnitude gain. (8)
(ii) Draw the circuit diagram with equation for V0 of an instrumentation amplifier and write down its important features and application. (8)
Or
(b) (i) Sketch the collector coupled astable multivibrator circuit. (4)
(ii) Determine period and frequency of oscillations for an astable multivibrator with components values R1 = 2 k , R2 = 20 k ,
C1 = 0.01 f, C2 = 0.05 f. (4)
(iii) Draw and explain the functional diagram of a 555 Timer. (8)
Anna univ CE 251 — STRENGTH OF MATERIALS
PART A — (10 ? 2 = 20 marks)
1. What is a rigid body and a deformable body?
2. The Youngs modulus of steel is 200 kN/mm2 and concrete is 20 kN/mm2. What is the modular ratio?
3. A cantilever beam is subjected to a moment M at free end. The length of the beam is L. What is the bending moment at fixed end?
4. What is point of contraflexure? Whether point of contraflexure will occur in a cantilever beam?
5. Sketch the shear stress variation across the I–beam cross section due to bending.
6. What is flitched beam?
7. A simply supported circular beam of span 4 m carries a 10 kN load at midspan. The cross section is 100 mm diameter. What is the maximum bending stress?
8. What is close coiled helical spring?
9. What is the diameter of Mohr’s circle if the principal stresses are 40 N/mm2 and 80 N/mm2.
10. Give two examples of conjugate beam with the corresponding real beam.
PART B — (5 ? 16 = 80 marks)
11. A simply supported beam of length 4 m carries two point loads 3 kN each at a distance of 1 m from each end. E = 2 ? 105 N/mm2. I = 108 mm4. Using conjugate beam method determine slope at each end and deflection under each load.
12. (a) Two vertical rods are loaded as shown in Fig. Q 12 (a). N/mm2 N/mm2. Find the stresses in steel and copper rods.
Fig. Q 12 (a)
Or
(b) A steel tube of 30 mm external diameter and 20 mm internal diameter encloses a copper rod of 15 mm diameter. The ends are rigidly joined. The temperature of whole assembly is raised by 190?C. N/mm2 = N/mm2 per ?C, per ?C. Calculate stress in the rod and the tube.
13. (a) Draw the shear force and bending moment diagrams for the beam shown in Fig. Q 13 (a)
Fig. Q 13 (a)
Or
(b) A beam of size 150 mm wide, 250 mm deep carries a uniformly distributed load of w kN/m over entire span of 4 m. A concentrated load
1 kN is acting at a distance of 1.2 m from the left support. If the bending stress at a section 1.8 m from the left support is not to exceed 3.25 N/mm2 find the load w.
14. (a) The stiffness of close coiled helical spring is 1.5 N/mm of compression under a maximum load of 60 N. The maximum shear stress in the wire of the spring is 125 N/mm2. The solid length of the spring (when the coils are touching) is 50 mm. Find the diameter of coil, diameter of wire and number of coils. C = 4.5 ? 104 N/mm2.
Or
(b) The stresses at a point in a strained member are shown in Fig. Q 14 (b). The greatest principle stress is 150 N/mm2. Find the value of q. Also find maximum shear stress at that point.
Fig. Q 14 (b)
15. (a) A cantilever beam 4m span carries a point load of 10 kN at free end. Find the deflection and rotation at mid–span using principle of virtual work. EI = 25,000 kNm2.
Or
(b) A simply supported beam of 10 m span carries a uniformly distributed load of 1 kN/m over the entire span. Using Castigliano’s theorem, find the slope at the ends. EI = 30,000 kNm2.
1. What is a rigid body and a deformable body?
2. The Youngs modulus of steel is 200 kN/mm2 and concrete is 20 kN/mm2. What is the modular ratio?
3. A cantilever beam is subjected to a moment M at free end. The length of the beam is L. What is the bending moment at fixed end?
4. What is point of contraflexure? Whether point of contraflexure will occur in a cantilever beam?
5. Sketch the shear stress variation across the I–beam cross section due to bending.
6. What is flitched beam?
7. A simply supported circular beam of span 4 m carries a 10 kN load at midspan. The cross section is 100 mm diameter. What is the maximum bending stress?
8. What is close coiled helical spring?
9. What is the diameter of Mohr’s circle if the principal stresses are 40 N/mm2 and 80 N/mm2.
10. Give two examples of conjugate beam with the corresponding real beam.
PART B — (5 ? 16 = 80 marks)
11. A simply supported beam of length 4 m carries two point loads 3 kN each at a distance of 1 m from each end. E = 2 ? 105 N/mm2. I = 108 mm4. Using conjugate beam method determine slope at each end and deflection under each load.
12. (a) Two vertical rods are loaded as shown in Fig. Q 12 (a). N/mm2 N/mm2. Find the stresses in steel and copper rods.
Fig. Q 12 (a)
Or
(b) A steel tube of 30 mm external diameter and 20 mm internal diameter encloses a copper rod of 15 mm diameter. The ends are rigidly joined. The temperature of whole assembly is raised by 190?C. N/mm2 = N/mm2 per ?C, per ?C. Calculate stress in the rod and the tube.
13. (a) Draw the shear force and bending moment diagrams for the beam shown in Fig. Q 13 (a)
Fig. Q 13 (a)
Or
(b) A beam of size 150 mm wide, 250 mm deep carries a uniformly distributed load of w kN/m over entire span of 4 m. A concentrated load
1 kN is acting at a distance of 1.2 m from the left support. If the bending stress at a section 1.8 m from the left support is not to exceed 3.25 N/mm2 find the load w.
14. (a) The stiffness of close coiled helical spring is 1.5 N/mm of compression under a maximum load of 60 N. The maximum shear stress in the wire of the spring is 125 N/mm2. The solid length of the spring (when the coils are touching) is 50 mm. Find the diameter of coil, diameter of wire and number of coils. C = 4.5 ? 104 N/mm2.
Or
(b) The stresses at a point in a strained member are shown in Fig. Q 14 (b). The greatest principle stress is 150 N/mm2. Find the value of q. Also find maximum shear stress at that point.
Fig. Q 14 (b)
15. (a) A cantilever beam 4m span carries a point load of 10 kN at free end. Find the deflection and rotation at mid–span using principle of virtual work. EI = 25,000 kNm2.
Or
(b) A simply supported beam of 10 m span carries a uniformly distributed load of 1 kN/m over the entire span. Using Castigliano’s theorem, find the slope at the ends. EI = 30,000 kNm2.
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