SRI RAMANUJAR ENGINEERING COLLEGE
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
UNIT 1 / DRIVE CHARACTREISTICS
SUB CODE / SUB NAME: EE3012 ELECTRICAL DRIVES
YEAR / SEM : III / VI PART A
1. List the types of load torques.
2. Compose the fundamental torque equation of motor load.
3. Explain the active load torques and passive load torques? Give example.
4. Explain the typical Elements of an Electric Drive.
5. Define electrical drive
6. Define regenerative braking
7. Compose the condition for steady state stability of motor
8. Draw the torque speed characteristics of a hoist load Mechanism.
9. Define Dynamic Braking
10. Explain the Different mode of operation of an electric drive.
11. Discuss the necessary condition to obtain the three Modes of operation of an electric drive.
12. Explain the types of electric braking. Give example is braking applicable for any type of motor.
13. Name the different types of load.
14. Illustrate a drive? How are they classified?
15. Explain the speed – torque conventions used in multi Quadrant operation.
PART B
1. Explain the Different mode of operation of an electric drive.
2. Give and Label the block diagram of electrical drive Systems.
3. Explain the speed – torque conventions used in multi Quadrant operation.(13)
4. Define how the following speed transitions are carried Out: (i) Increase in speed in same
direction, (ii) Decrease in speed in same direction and (iii) Speed reversal.(13)
5. Discuss in detail the multi quadrant dynamics in the speed –torque plane. (6)
6. Explain the four quadrant operation of low speed hoist in detail. (6)
7. Compose the mathematical condition to obtain steady State stability of equilibrium point.
8. Solve a motor drives two l o a d s . One has rotational Motion. It is coupled to the motor through a
reduction gear with a = 0.1 and efficiency of 90%. The load has a moment of inertia of 10 kg-m2 and
a torque of 10 N-m. Other load has translational motion and consists of 1000kg weight to be lifted
up at a uniform speed of 1.5 m/s. coupling between this load and the motor has an efficiency of 85%.
Motor has inertia of 0.2 kg-m2 and runs at a constant speed of 1420 rpm.Determine equivalent
inertia referred to the motor shaft and power developed by the motor.
UNIT 2 CONVERTER /CHOPPER FED DC MOTOR DRIVE
PART-A
1. What is the speed control method of DC motor?
2. What are the advantages in operating chopper at high frequency?
3. Define TRC.
4. Write the expression for average output voltage of full converter fed dc drive.
5. Write the speed torque equation of asingle phase fully controlled converter fed separately excited dc
motor drive.
6. What is armature voltage control?
7. Mention the method of armature voltage control dc motor
8. List the disadvantages of frequency modulation on generating PWM waveform?
9. List out the drawbacks of DC-AC converter and FED DC converter.
10. Mention the application of chopper fed dc drive.
11. What are the disadvantages of chopper FED DC drive?
12. State the function of freewheeling diode in phase control rectifier.
13. List out the drawbacks of rectifier FED DC drive.
14. Why does armature voltage control not preferred for speed above the rated value in DC motor?
15. What are the types of control strategies used in a chopper FED DC drive?
PART-B
1. Explain the steady state analysis of Single Phase Fully Controlled Converter Fed Separately Excited
D.C Motor Drive with continuous and discontinuous conduction mode. (13)
2. Explain the Four Quadrant chopper fed DC Separately Excited D.C Motor Drive with necessary
Diagram.(13)
3. Explain the Three Phase Fully Controlled Converter Fed Separately Excited D.C Motor Drive with
Necessary diagram.(13)
4. Explain the different control strategies of chopper.
5. Discuss the four quadrant operation of DC-DC converter.
6. (i) A 400V, 875 rpm, 150A separately excited dc motor has An armature resistance of 0.06 Ω. It is
Fed from a single phase fully controlled rectifier with an ac source voltage of 440V, 50Hz. Assuming
Continuous conduction, Calculate (i)Firing angle for rated motor torque and (-750) Rpm (ii) Motor
Speed for α=160◦ and rated torque. (7)
7.i) A chopper used to control the speed of a separately excited dc motor, has supply voltage of 430 V,
Ton=15ms, Toff=5ms. Assuming continuous conduction of motor current, Estimate the average
load current when the motor speed is 3000rpm. Assume voltage constant Kv=0.5V/rad/sec and
Ra=4ohms. (6)
UNIT 3 INDUCTION MOTOR DRIVES
PART A
1. Justify Why stator voltage control is suitable for speed
Control of induction motors in fan and pump drives.
2. Summarize different methods of braking applied to induction motor.
3. What are the advantages of induction motor over DC Motor
4. Discuss different methods of speed control of induction motor.
5. Tell the drawbacks of stator voltage controlled Induction Motor drive.
6. Define three regions in speed vs torque characteristics of induction motor.
7. Compare CSI fed drives and VSI fed drives
8. Compose the merits and demerits of voltage fed inverters Controlled drives.
9. Write any two advantages of closed loop control system.
10. List the application of stator voltage control method of 3 phase induction motor drive
11. What is slip power?
12. What are the advantages of V/F control?
13. How is the braking action produced in plugging?
14. What is meant by regenerative braking?
15. What is meant by plugging?
PART-B
1.Discuss in detail with suitable diagrams and waveforms The v/f control
Technique of speed control method of Induction motor.(13)
2.Describe the variable frequency operation of induction Motor in closed loop with
Constant - gap flux. (13)
3. Explain the speed control scheme of induction motor drive With stator voltage
Control and stated is advantage of this Method.(13)
4..Describe the close loop speed control of VSI fed and CSI fed induction motor drives.(13)
5. Explain the working of CSI fed induction motor drive. (13)
6. Explain the working of VSI fed induction motor drive. (13)
7. Show and explain with a neat diagram the field weakening mode control of
Induction Motor drives. (13)
UNIT 4 SYNCHRONOUS MOTOR DRIVES
PART A
1. Justify why a self-controlled synchronous motor is free from hunting oscillations?
2. Discuss why v/f ratio is kept constant up to base speed and V constant above base speed in
variable frequency control.
3. What is self-control of synchronous motor.
4. Compose the merits and demerits of PMSM
5. Illustrate when a synchronous motor said to be self-controlled?
6. Show the necessity of delay unit in a open loop v/f control of synchronous motor.
7. Why is damper winding absent in self- controlled Synchronous motors?
8. Explain the modes of adjustable frequency control in synchronous motor drives.
9. How the power factor of a synchronous motor can be controlled?
10. What is slip power recovery scheme?
11. Name the two controllers employed in the closed loop control of synchronous motor drives.
12. What are the types and advantages of permanent magnet AC synchronous motor drives?
13. Write notes on brushless excitation?
14. What is the difference between true synchronous and self-control modes of synchronous motor
drives?
15. Define torque torque angle of synchronous motor.
PART-B
1.(i) Discuss briefly separate controlled mode of synchronous motor in detail. (7)
(ii) Explain self- control of synchronous motor drive in detail.(6)
2. Explain margin angle control of synchronous motor drive. (13)
3. Describe the open loop v/f control of synchronous motor drives in detail. (13)
4. Discuss in detail the construction, Principle of operation and application of permanent magnet
synchronous motor. (13)
5. Describe b r i e f l y the power factor angle control of synchronous motors. (13)
6. Explain the control of synchronous motors on adjustable frequency supply. (13)
7. Compose the closed loop control of synchronous motor with neat block diagram.(13)
8. A 500kW, 5 phase, 5.5 kV, 50 Hz, 0.8 lagging power factor, 4 pole, star connected
Synchronous motor has the following parameters Xs=15Ω, Rs=0.Rated field current is 10A.
Calculate armature current and power factor at half the rated torque and field current.(1
UNIT 5 DESIGN OF CONTROLLERS FOR DRIVES
PART A
1. Discuss the roles of inner current control and outer speed control loops?
2. List the methods of speed sensing
3. Write down the transfer function expression of converter.
4. Give the advantages of PI controller
5. Describe field weakening mode control.
6. Name any four simulation software packages that can be used for electrical drives.
7. List the advantages of closed loop speed control.
8. Discuss the role of current limiter in the closed loop control of DC drives.
9. When can a synchronous motor be load commutated?
10. Show the transfer function of DC motor load system
11. Explain how speed feedback achieved in speed controller design?
12. What are the modes of adjustable frequency control in synchronous motor drives?
13. Write the transfer function expression for speed controller
14. What is meant by mechanical and electrical time constant?
15. What are the function of feedback loops in an electrical drive?
PART B
1. Derive and explain from basic principles the transfer function for separately excited DC
motor load system with converter fed armature voltage control.(13)
2. Explain the closed loop operation of armature voltage control method and field weakening
mode control for Dc drive.(13)
3. (i) Discuss the design procedure for current controller of an electric drive (7)
(ii) Mention the factors involved in converter selection and equations involved in
Controller characteristics.(6)
4. Give the design procedure for speed controller of an electrical drive system with necessary
diagrams.(13)
5. Describe the current controller design using
(i) P controller(6)
(ii)PI controller for a separately excited dc motor drive systems.(7)
6. Design the speed controller of converter fed separately excited dc motor with inner current
control and outer speed control loops.(13)
