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Electrical Engineering Objective Questions { DC Motors }

127. In a de machine, maximum losses occur due to
A. iron losses
B. mechanical losses
C. copper losses
D. none of these

128. The nominal power printed on the name plate of any motor signifies the
A. power drawn in kVA
B. output power at the shaft
C. power drawn in kW
D. the gross power

129. The following control method provides a constant torque drive
A. shunt armature control
B. motor field control
C. armature voltage control
D. none of these

130. In a dc shunt motor if the supply voltage is reduced by 15%, the following quantity will increase
A. starting torque
B. full load current
C. full load speed
D. all of these

131. During the normal operation of a series motor, if the field circuit suddenly opens,the motor
A. speed will increase
B. speed will drop
C. will stop
D. speed will remain unchanged

132. In an overload dc motor, main danger arise due to
A. overheating of bearings
B. overheating of windings
C. overheating of bus bars
D. starter getting damaged

133. The maximum permitted temperature in dc motor windings is usually
A. 10?C to 20?C
B. 20?C to 30?C
C. 40?C to 50?C
D. 80?C to 100?C

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