TS ECET EEE 2020-4

1. Match the following

Group-1	Group-2
P. Short pitch winding	l) cylindrical rotor type alternators
Q. Coil span factor	m) salient pole rotor type alternator
R. Concentrated winding	n) cosα/2 where α=short pitch angle
S. Turbo-alternators	o) improved waveform of the generated emf per phase

A. P-m, Q-n, R-l, S-o
B. P-o, Q-n, R-m, S-l
C. P-o, Q-n, R-m, S-l
D. P-m, Q-n, R-l, S-m

Answer : B. P-o, Q-n, R-m, S-l
Explanation:-

2. With constant excitation(Ef), terminal voltage(Vt) and synchronous impedance(Zs), the condition for maximum input to generator is

A. Load angle(δ) = Impedance angle(θ)
B. Load angle(δ) =180°-Impedance angle(θ)
C. Load angle(δ) =90°-Impedance angle(θ)
D. Load angle(δ) =90°+Impedance angle(θ)

Answer : B. Load angle(δ) =180°-Impedance angle(θ)
Explanation:-

3. Which of the following statements is/are correct?

A) When a 3phase synchronous motor is running at synchronous speed, the samper windings produces damping torque
B) Damper winding is provided in a poly phase synchronous motor in order to prevent hunting
C) A synchronous condensor is an over excited synchronous motor without mechanical load
D) While starting a 3phase synchronous motor, its field winding should be open circuited.

Choose the correct option from the following

A. A,B,C and D
B. C and D only
C. A,B and C only
D. B and C only

Answer : D. B and C only
Explanation:-

4. The ability of the synchronous motor to remain in synchronism under rated load conditions is called

A. starting torque
B. pull-in torque
C. Accelerating torque
D. Pull-out torque

Answer : D. Pull-out torque
Explanation:-

5. The stator current and power factor of a 3phase induction motor under No-load cndition are respectively in the range of

A. 10 to 14% of rated current and 0.1 to 0.3 lagging
B. 30 to 50% of rated current and 0.85 to 0.88 lagging
C. 10 to 14% of rated current and 0.85 to 0.88 lagging
D. 30 to 50% of rated current and 0.1 to 0.3 lagging

Answer : D. 30 to 50% of rated current and 0.1 to 0.3 lagging
Explanation:-

6. A 4 pole,3 phase, 50Hz induction motor has rotor resistance of 1.5ohm runs at 1400 rpm. The rotor resistance equivalent of mechanical power output is ____ ohms

A. 21
B. 22.5
C. 1.5
D. 42

Answer : A. 21
Explanation:-

7. In a 3-phase SCIM, applied voltage is reduced to y times its rated value. Then its starting line current from mains and starting torque by auto transformer starting would reduce respectively from their corresponding direct switch values by a factor of

A. y*y^2
B. y^2*y
C. y^2*y^2
D. y*y

Answer : C. y^2*y^2
Explanation:-

8. The following tests are conducted on a 3-phase induction motor

P: No load test
Q: Blocked rotor test
R: stator resistance test

Which of the above tests are required to draw the complete circle diagram of 3-phase induction motor?

A. P & Q only
B. Q & R Only
C. P,Q and R
D. P and R only

Answer : C. P,Q and R
Explanation:-

9. A six pole, 50 Hz single phase induction motor is running at 900 rpm. its slip with respect to forward field and backwards field is respectively

A. 1.9 and 0.1
B. 0.1 and 1.9
C. 1 and 1
D. 0 and 2

Answer : B. 0.1 and 1.9
Explanation:-

10. Which of the following statements is/are correct in case of universal motors?

A) The speed torque characteristics is a typical shunt type
B) The no-load speed is very low
C) the speed torque characteristic od DC operation would lie some what higher for AC operation
D) used in vacuum cleaners and portable tools

Choose the correct option from the following

A. C and D only
B. A and B only
C. A,B and C only
D. A,C and D only

Answer : A. C and D only
Explanation:-