Electrical Machines Questions and Answers – Methods of Excitation

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Methods of Excitation in DC Machines”.

1. Consider a DC generator running at the rated speed of 2000 rpm, suddenly there is an insulator falls on the field circuit and breaks it. Then __________
a) the motor stops in a few rounds
b) it continues to run but as dc motor
c) it continues to run as a motor
d) none of the mentioned
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2. If a self excited DC generator is failed to run, this refers to ________________
a) zero residual voltage
b) field MMF, that it is not cumulative
c) resistance is greater than critical resistance
d) any of the mentioned
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3. The self-excited dc generator with gradual build up of residual voltage and EMF corresponds to __________
a) positive feedback
b) negative feedback
c) saturation
d) any of the mentioned
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4. The critical resistance refers to __________
a) the resistance above which machine does not excite
b) the resistance below which machine does not excite
c) the resistance at which machine does not excite
d) any of the mentioned
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5. If a DC shunt generator fails to start, the most primitive action would be __________
a) reversing field connection to armature
b) reversing direction of rotation
c) any of the mentioned applicable ways
d) none of the mentioned
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6. Flashing is used to __________
a) temporarily excited field from a battery source for large DC generator
b) temporarily excited field from a battery source for small DC generator
c) temporarily excited field from a battery source for large DC motor
d) temporarily excited field from a battery source for large DC motor
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7. A series generator, having external characteristics which is a straight line through 0 to 50 V at 200 A is connected as a booster, between a station bus-bar and feeders of 0.5 ohm resistors. The voltage at the far end of feeder at current of 50 A is?
a) 25 V
b) 17 V
c) 8 V
d) 50 V
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8. The number of parallel paths in the armature is increased by __________
a) increasing number of magnetic poles
b) decreasing number of magnetic poles
c) lap number of magnetic poles
d) using more brushes
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9. A dc series generator as armature and field connections are reversed, the generator __________
a) stops
b) opposite direction
c) same direction
d) none of the mentioned
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10. _____________ is responsible for mechanical power output of a DC motor.
a) Electrical input power
b) Any of the mentioned
c) Air-gap flux
d) Armature emf
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Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.