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Electrical Engineering Objective Questions { Synchronous Motors }

134. An over-excited synchronous motor behaves as
A. a resistor
B. an inductor
C. a capacitor
D. none of the above
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135. At full-load, the rotor poles of a synchronous motor are displaced by a mechanical angle of 1? from their no-load position. If the machine has 40 poles, then torque angle is
A. 40? electrical
B. 20? electrical
C. 100 electrical
D. none of the above
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136. The mechanical power developed by a synchronous motor is independent of
A. applied stator voltage
B. torque angle
C. field excitation
D. speed
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137. When a synchronous motor is pulled out of synchronism, the stator current
A. becomes zero
B. is increased too much
C. is decreased too much
D. remains unchanged
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138. A synchronous capacitor is an over-excited motor running at
A. full-load
B. half full load
C. no-load
D.pone of the above
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139. A synchronous motor delivers reactive power when
A. over-excited
B. under-excited
C. normally excited
D. none of the above
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140. When a unity p.f. synchronous motor is operated at a leading p.f., it results in
A. more than rated horsepower output
B. more than rated stator current
C. less than rated horsepower output
D. none of the above
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