TS ECET EEE 2020-10

1. DIAC is _______ directional device

A. Uni
B. Tri
C. Bi
D. Non

Answer : C. Bi
Explanation:-

2. Match the following devices with their maximum frequency of operation

i) phase controlled SCR	a) 100KHZ
ii) IGBT	b) 25KHZ
iii) BJT	c) 60HZ
iv) GTO	d) 10KHz

Choose the correct option from the following

A. i-c, ii-a, iii-d, iv-b
B. i-c, ii-a, iii-b, iv-d
C. i-a, ii-c, iii-d, iv-b
D. i-a, ii-c, iii-b, iv-d

Answer : B. i-c, ii-a, iii-b, iv-d
Explanation:-

3. Which of the following is/are transistors?

A. BJT
B. MOSFET
C. BJT & MOSFET
D. SCR

Answer : C. BJT & MOSFET
Explanation:-

4. The input frequency of a cyclo converter is 50HZ what can be its expected output frequency?

A. 40HZ
B. 30HZ
C. 10.5 HZ
D. 6.25 HZ

Answer : D. 6.25 HZ
Explanation:-

5. A single phase full converter is feeding a load which draws a constant load current of 20A what is the average thyristor current?

A. 20A
B. 10A
C. 20√2 A
D. 20/√2 A

Answer : B. 10A
Explanation:-

6. Consider a single phase full bridge voltage source inverter with thyristor switches. What type of load commutation circuit is not needed for thyristors?

A. R-load
B. R-L Load
C. RLC over damped
D. RLC under damped

Answer : D. RLC under damped
Explanation:-

7. Match the following converters with corresponding best suitable applications

i) cyclo converter	a) Uninterruptable power supplies
ii) inverter	b) DC traction motors
iii) Phase controlled rectifier	c) solar energy conversion
iv) chopper	d) Megawatt power AC drives

Choose the correct option from the following

A. i-d, ii-a, iii-c, iv-b
B. i-a, ii-d, iii-c, iv-b
C. i-d, ii-a, iii-b, iv-c
D. i-a, ii-b, iii-c, iv-b

Answer : C. i-d, ii-a, iii-b, iv-c
Explanation:-

8.

Statement I: Inverters are used to control the speed of AC drives

Statement II: Total harmonic distortion produced by square wave inverter is zero.

Choose the correct option from the following

A. Both statements I and II are individually true and statement II is the correct explanation of statement I
B. Both statements I and II are individually true and statement II is NOT the correct explanation of statement I
C. Statement I is true but statement II is false
D. Statement II is true but statement I is false

Answer : C. Statement I is true but statement II is false
Explanation:-

9. A star connected squirrel cage induction motor has the following ratings: 400V,50HZ,4-Pole,1370 rpm.Motor is controlled by a voltage source inverter at constant V/f ratio. What is the value of frequency for a speed of 1070 rpm at full load torque?

A. 50HZ
B. 30HZ
C. 40HZ
D. 60HZ

Answer : C. 40HZ
Explanation:-

10. A three phase induction motor is driving a load whose torque Vs speed characteristics is a parabola. The best suitable speed control technique for this arrangement is

A. voltage control
B. frequency control
C. V/f control
D. Rotor resistance control

Answer : A. voltage control
Explanation:-