Year 2024

Week # 2 Quiz 1

Q1. The four no-load speeds of three-phase induction motors operating on 400 V, 50 Hz supply are 576 rpm, 720 rpm, 1440 rpm, and 2880 rpm. The number of poles of the motor, respectively, are

Q2. A 6-pole, 50 Hz, 3-phase induction motor has a full load speed of 950 rpm. What will be the speed at half-load?

Q3. For induction motor, operating at slip of 3% the ratio of gross power output to air gap power is equal to

Q4. A 200/400 V, 20 kVA, 2-winding transformer is connected as an auto-transformer to transform 600 V to 200 V. Calculate the KVA rating of the auto-transformer.

Q5. The condition for maximum efficiency of a D.C. generator is

Q6. A 500 KVA, 3 Phase transformer has iron losses 300 W and full load copper loss 600 W. The percentage load at which the transformer is expected to have maximum efficiency?

Q7. A 3000/300 V single phase transformer takes 0.8 A at power factor of 0.4 on open circuit. Find the magnetizing reactance

Q8. The peak value of phase MMF is Fmax, the peak value of rotating field caused by three phase is

Q9. A transformer has copper loss of 1.5 % and reactance of 3.5 % when tested on load. If its full load regulation is -0.9 % find its power factor.

Q10. The desirable properties of transformer core material are