Design of Electrical Machines Practice Test 4

1. Which among the following are the applications of synchronous motors?

compressors

blowers

fans

compressors, fans, blowers

2. What is the formula for stator turns per phase?

stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux * stator winding factor

stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux * stator winding factor

stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux / stator winding factor

stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux / stator winding factor

3. For the lower values of current, round conductors would be convenient to use.

true

false

4. What is the relation between the number of poles and pole pitch with power factor?

number of poles increases, pole pitch increases, bad power factor

number of poles increases, pole pitch decreases, good power factor

number of poles increases, pole pitch increases, bad power factor

number of poles increases, pole pitch decreases, good power factor

5. How are the bearing cooled in the construction?

natural cooling

forced cooling

oil cooling

air cooling

6. What is the rating of the engine driven generators?

750 MW

1000 MW

700 MW

20 MW

7. What is the formula for dispersion coefficient?

dispersion coefficient = magnetizing current + ideal short circuit current

dispersion coefficient = magnetizing current - ideal short circuit current

dispersion coefficient = magnetizing current * ideal short circuit current

dispersion coefficient = magnetizing current / ideal short circuit current

8. In what type of generator is the thick rolled steel discs made use of?

generators running at 600 rpm and above

generators running at 400 rpm

generators running at 600 rpm

generators running at 500 rpm

9. Why are damper windings used in the construction of hydro-generators?

to reduce the oscillations

to reduces voltage surges

to control losses

to increases efficiency

10. What is the formula for dispersion coefficient?

dispersion coefficient = 0.838 * 10⁶ * 3.14 / air gap length * effective specific permeance / pole pitch * (window space factor)² * number of slots per pole per phase

dispersion coefficient = 0.838 * 10⁶ * 3.14 * air gap length * effective specific permeance / pole pitch * (window space factor)² * number of slots per pole per phase

dispersion coefficient = 0.838 * 10⁶ * 3.14 * air gap length * effective specific permeance * pole pitch * (window space factor)² * number of slots per pole per phase

dispersion coefficient = 0.838 * 10⁶ * 3.14 * air gap length / effective specific permeance / pole pitch * (window space factor)² * number of slots per pole per phase