Explanation: The rotor core loss is almost negligible because of reduced frequency of the flux reversals (equal to slip frequency, sf) in the rotor, and Pe∝f2 and Ph∝f. ( Pe = eddy current losses, Ph = hysteresis losses) 7. The pole shoes in DC and synchronous machines are laminated to reduce _____________
A. Resistance losses
B. Pulsation or pole-face losses
C. Mechanical losses
D. None of the mentioned
Answer:A
Explanation: The rotor core loss is almost negligible because of reduced frequency of the flux reversals (equal to slip frequency, sf) in the rotor, and Pe∝f2 and Ph∝f. ( Pe = eddy current losses, Ph = hysteresis losses) 7. The pole shoes in DC and synchronous machines are laminated to reduce _____________
A. Resistance losses B. Pulsation or pole-face losses C. Mechanical losses D. None of the mentioned
Explanation: The pulsations in flux density wave arising from slot openings cause losses in the field iron, particularly in the pole faces. This loss occurring due to relative motion, between field poles and slotted armature, is referred to as pulsation loss. 8. What percentage of the rated output for DC machine and synchronous machine is taken as stray load losses respectively?