DGM RESOURCES COMPARISON

MICROGRID - UNIT 1 PART A WITH ANSWERS

MUST READ QUESTIONS Reg 2013 – SSD

MUST READ QUESTIONS – SSD

UNIT-1

1.     Equations governing motor load dynamics

2.    Steady state stability

3.    Multi quadrant dynamics

4.    Acceleration, deceleration, starting & stopping  (MODES OF OPERATION)

5.    Typical load torque characteristics (5)

6.     Selection of motor (5)

7.     PROBLEMS

UNIT-5

1.     Transfer function for DC motor / load and converter

2.   Closed loop control with Current and speed feedback–armature voltage control and field weakening mode

3.   Design of current controllers

4.   Converter selection and characteristics (5)

UNIT-4

      1   V/f control and self control of synchronous motor
      2.   Margin angle control
      3.   Power factor control (5)
      4.   Permanent magnet synchronous motor (SINUSOIDAL& TRAPEZOIDAL)
     5.    PROBLEMS

UNIT-2

1. Steady state analysis of the single converter fed separately excited DC motor Drive–continuous and discontinuous conduction
2. Steady state analysis of the three phase converter fed separately excited DC motor Drive–continuous and discontinuous conduction
3. Time ratio and current limit control (5)
4. 4 quadrant operation of converter / chopper fed drive.
5. PROBLEMS

UNIT-3

1. Stator voltage control
2. V/f control
3. Constant air gap flux
4.  Voltage / current fed inverter – closed loop control
5. PROBLEMS

BIOMASS VIDEO

MEMS QUESTION BANK WITH ANSWERS

MEMS ANNA UNIVERSITY SYLLABUS

MEMS UNIT 4 MATERIAL

MEMS UNIT 3 MATERIALS

MEMS UNIT 1& 2 MATERIALS

MEMS PART A QUESTIONS & ANSWERS

INTRODUCTION - MEMS TWO MARKS

SENSORS AND ACTUATORS -1 TWO MARKS

MEMS OVERVIEW & INTRODUCTION

Polyimides Used in the Manufacturing of Micro Systems

Placement Preparation - AMCAT

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MEMS - PIEZO SENSORS AND ACTUATORS QUESTION BANK

PART-A 

ANSWER THE FOLLOWING

1.     What are the advantages of piezoresistive sensor?

2.     What is meant by piezo resistive sensor

3.     List piezoelectric materials?

4.     Define piezoelectric effect.

5.     Write the equation of piezo resistivity.

6.     Discuss about the materials that are used as piezoresistors

7.     List the applications of piezoresistive sensors.

8.     Discover the need of acoustic sensors.

9.     Describe PVDF

10.  Why ZnO is used instead of PZT?

PART-B

ANSWER ALL THE QUESTIONS

1. Define Acoustic sensor. Examine the steps involved in fabrication process of PZT piezoelectric Microphone

     2. Explain about the fabrication steps involved in cantilever piezoelectric                            accelerometer.

     3.   Discuss about the properties of the materials used in the fabrication of   

         piezoelectric  sensors

Comparison of the speed control methods of shunt/separately excited dc motor

S. No.	Basis of comparison	Significance	Armature resistance control	Field control	Ward Leonard Control
1.	Limit, range and hardness of speed control	Signifies the ratio of speed with load	The speed in the range of zero or almost crawling to base speeds is possible. The range of speed control depends on load.	Speeds below base speed require field currents above the rated value. Hence it is not employed for speeds below base speed.	An elegant method for smooth variation of speed over a wide range. Speed reversal is possible by reversing the generator field.
2.	Smoothness of speed control	Signifies the number of steady speeds in the operating range.	In large drives speed control is obtained by varying the armature resistance using contactors.	The field circuit is low power one. The resistance in the field circuit can be smoothly varied	Speed control is achieved by controlling the generator field.  The smoothness with which the generator field can be varied decides the smoothness of speed control.
3.	Economics of speed control	Decided by the efficiency of the motor, maintenance and overall cost.	The power loss in the armature resistance reduces the efficiency. The efficiency is very poor, particularly at low speeds.	The method is economical. The efficiency is not very much affected, because the field losses decrease and rotational losses increases. The method is well suited for constant power loads.	High initial cost both for conventional and static. Efficiency is better than armature resistance control.
4.	Stability of operation	The capacity of the drive to return to its original state or a state of new operating conditions following a disturbance in speed or torque	The stability is decided by the torque driven at given speed.	The weak flux conditions in the machine are prone to increase degree of armature reaction. The armature reaction may cause stability problems.	Stability is very good at speeds below base speed. At higher sped he stability is a matter of concern.
5.	Direction of speed control	Signifies the possibility of speed control below and above base speeds.	Only speeds below base speed up to zero are possible.	Only speeds above base speed are possible due to field rating.	Speed variation below base speed by armature voltage control and above base speed by field control.
6.	Permissible load	Signifies Whether the machine is over loaded or under loaded in its speed range and thus utilisation of the machine.	Suitable for constant torque loads	Suitable for constant power loads	Suitable for both constant power & torque loads

DESIGN OF CONTROLLERS QUESTION BANK

1.     Discuss  the current controller design  using i) P controller ii) PI controller  for a separately excited  dc motor drive system.                                                            

2.     Derive the closed loop transfer function  of converter fed separately excited dc motor

3.   A 50KW, 240 V, 1700 rpm separately excited dc motor is controlled by converter. The field current is maintained at field current 1.4 A and the machine back emf constant Kv=0.91V/A/rad/s. The armature resistance is Rm =0.1 Ω and the viscous friction constant is B= 0.3 NM/rad/sec. The amplification of speed sensor is K1 = 95mV/rad/s and the gain of power controller is K2 = 100. i) Determine the reference voltage Vr to drive the motor at the rated speed. ii) If the reference voltage is kept unchanged, determine the speed at which the motor torque develops rated torque.                16

4. From basic principles derive the transfer function for separately excited DC motor load system.                                                                                                                     

5.     Explain the step by step procedure  for the design of  current controller                        

6.   Explain the closed loop speed control   for armature  voltage control  and field weakening mode for a dc drive                                                                                      

7. Explain the factors involved in converter selection and equations involved in controller characteristics.                                                                                                            

The following basic features govern the design of speed control of an electric motor.

i) Range of speed control

ii) Smoothness of speed control

iii) Economic justifiability

iv) Stability of operation

v) Direction of speed control

            vi) Permissible load at different speed

SYNCHRONOUS MOTOR DRIVE QUESTION BANK

1.    Explain the self controlled  mode of operation of a synchronous motor                            

2.    Explain constant margin angle control technique of self controlled synchronous motor drive employing load commutated thyristor inverter.                                                    

3.     Discuss the advantages  and disadvantages of margin angle control                              

Advantages:

i) The commutation failure is prevented.

 ii) The maximum power output can be increased by simultaneous control of the field current to compensate for armature relation

iii) There is improvement in the power factor

iv) the torque pulsations under light load conditions are reduced. Also the ripple content of the dc link current decreases.

Disadvantages:

The main disadvantage is limited speed range. To avoid this the margin time is specified and it is kept constant.

4.    Briefly explain the types of PMSM                                                                                  

5.    Explain the vector control  of sinusoidal  SPM in constant torque region                      

6.    A 3 phase 400 V , 50 hz, 6 pole , a star connected  round  - rotor synchronous motor has Zs = 0+j2 Ω . Load torque, proportional to speed squared, is 340 Nm at rated synchronous speed.  The speed of the motor is lowered by keeping V/F constant and maintaining unit PF by field control of the motor. For the  motor operation  at 600 rpm, calculate i)  supply voltage ii)  armature current iii) excitation angle  iv) load angle  v) pull out torque .  Neglect rotational losses.                                                                    

7.    Brief about  trapezoidal PMAC motor drive                                                                    

8.    Explain the open loop V/F control  of synchronous motor drive                                    

9.     Explain the construction and working of permanent magnet synchronous Motor.     

10.  What is meant by commutatorless DC motor?                                                              

11.  Write in detail about power factor angle control of synchronous motors.                       

             With neat block diagram, explain the variable frequency control of multiple synchronous                          motors.                                         

INDUCTION MOTOR DRIVE QUESTION BANK

1.     Explain the voltage /frequency  control of an induction motor drives             

2.     Explain the closed loop speed control of CSI fed induction motor drive.        

3.  With necessary diagram explain the vector control of induction motor drive.                 

4.  Explain constant air gap flux based closed loop v/f control technique of induction motor drive in detail with neat sketch and necessary equations.                                      

5.   Make a  detailed comparison  between  VSI and CSI fed  induction motor drives           

6.  Explain in detail the static rotor resistance control in the induction motor drive.

7.  Explain about VSI induction motor drive and also closed loop control for VSI induction motor drives.                                                                       

8.  Highlight the features of an induction motor fed from a square wave inverter.                

9.     Write a short notes on  energy efficient drives                                                   

Energy saving is achieved by operating the induction motor at optimum voltage values. The energy saving depends on the following factors.

i) Duty cycle of motor: Energy saving is larger in drives which operates at low duty cycle.

ii) Operation with overvoltage’s:

iii) Quality of motor design

iv) Over sizing of motor

10. A three phase 60 KW, 4000 rpm, 460 V, 60 Hz, 2 pole star connected induction motor has the following parameters. Rs = 0.2 Ω Rr=0.28Ω, Xs=0.3Ωand Xm=11Ω. The motor is controlled by by varying the supply frequency. If the breakdown torque requirement is 70 Nm. calculate supply frequency and speed ω_m at the maximum torque.

11. A 2.8 KW, 400 V,50 Hz,4pole 1379 rpm, delta connected squirrel cage induction motor has following parameters referred to the stator Rs = 2 Ω, Rr =5 Ω, Xr=5 ΩXm =80 Ω. Motor speed is controlled by stator voltage control. When driving a fan load it runs at rated speed and rated voltage.  Calculate motor terminal voltage, current and torque at 1200 rpm.           

12.              A 3 phase, 50 Hz induction motor has the following parameters for its equivalent circuit R1=R2=0.02 Ω and X1=X2=0.1 Ω is to be operated at one half of its rated voltage and 25 Hz frequency. Calculate i) the maximum  torque at this rated  voltage and  frequency operation  in terms  of its  normal value  and ii)  the starting torque at this reduced frequency  and voltage in terms  of its normal value.

13.   Explain the  four modes of operation  of a static  scherbius drive 16

14. Why  a cycloconverter fed induction motor  drive  is preferred over  inverter  controlled  synchronous motor drive  for low speed applications

     15. Explain the  stator voltage control  of induction motor drive