169. In a synchronous machine, the electric circuits are armature circuit, field circuit and damper circuit and Xd is d-axis synchronous reactance; X'd is d-axis transient synchronous reactance and X"d is d-axis sub-transient synchronous reactance. If there is no damper winding,then
A. X'd = X"d
B. X"d = Xd
C. X'd = Xd
D. Xd = X'd = X"d
170. An alternator of 400 kW is driven by a prime mover of speed regulation 4% and another alternator of 200 km is driven by a prime mover of speed regulation 3%. The total load they can take, without overloading either of the machines is
A. 600 kW
B. 500 kW
C. 450 kW
D. 400 kW
171. Consider the following statements : Modern alternators are designed for large airgap to have 1. large inherent regulation. 2. very stable parallel operation. 3. higher stability limit. 4. sinusoidal mmf distribution. Which of these statements are correct?
A. 1, 2 and 3
B. 2, 3 and 4
C. 1, 3 and 4
D. 1, 2 and 4
172. To calculate the full-load voltage regulation of a synchronous generator at any power factor using mmf method, it is required to have
A. open-circuit and short-circuit characteristics
B. open-circuit and zero power factor characteristics
C. open-circuit characteristics, field current at rated short-circuit current and armature resistance
D. short-circuit characteristic, zero power factor characteristics and armature resistance
173. An alternator is operating on infinite bus. It will develop maximum synchronizing power when it is operating at
A. no load
B. full load
C. its steady state stability limit
D. any load
174. A 3-phase cylindrical rotor alternator is delivering rated power to a grid at its rated power factor. On account of some fault, steam supply to the turbine of the alternator is cut-off. The alternator would.
B. continue running as an alternator at synchronous speed Ns and deliver active power to the grid
C. continue running as a synchronous motor at Ns and deliver reactive power to the grid.
D. continue running as a synchronous motor at Ns and draw reactive power from the grid.
Page 25 of 25