Quiz

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 single phase transformer when supplied from a 220V, 50Hz supply has eddy current loss of 50 W. If the transformer is connected to a voltage of 330 V, 50 Hz, the Eddy current loss will be

Q3. A three phase, 10 kW, 4-pole, 50 Hz induction motor has full load speed of 1440 rpm. The friction and windage loss of the motor at this speed is 500 W. Calculate the rotor copper loss.

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. A 10-pole induction motor is supplied by a 6-pole alternator, which is driven at 1400 rpm. If the motor runs with a slip of 5%, what is its speed?

Q6. The frequency of the supply to the stator of an 8-pole induction motor is 50Hz and the rotor frequency is 3Hz. The slip is_________.

Q7. A \(\frac{2200}{1100}\)V, 50 Hz single-phase transformer having a negligible winding resistance operates from a variable voltage, variable frequency supply such that \(\frac{V}{f}\)is constant. Which of the following options is correct about the range of frequencies?

Q8. A shunt generator delivers 195 A at a terminal p. d. of 250 V. The armature resistance and shunt field resistance are 0.02 Ω and 50 Ω respectively. The value of generated EMF is                   .

Q9. A DC shunt motor takes 5A at 100V when running light. Shunt field resistance is 50 ohm and armature resistance is 0.2 ohm. What will be driving power?

Q10. If 'Pm' is the gross mechanical power developed, 'Pcu' is the rotor copper loss and 's' is the slip of induction motor, then the ratio of rotor copper loss to the gross mechanical power developed is ________ .