Electrical Machines Objective Questions
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An ideal DC generated is one that has _____________ voltage regulation.
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Wave winding is employed in DC machine of
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The magnetic field which initially induces emf in the armature in a self excited DC generator is because of
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What is the necessity of copper brushes in a dc motors?
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The sparking at the the brushes, in a DC machines is due to
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Resistance commutation is used generally in case of
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A commutator with a diameter of 50 cm rotating at 1000 rpm. For a brush width of 1.5 cm, find the time of commutation in ms.
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A 4 pole DC shunt generator having a wave winding supplies 50 lamps, each of 60 W at 120 V. The armature and field resistance are 0.2 Î© and 60 Î© respectively. The current in each armature conductor is
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DC generator will not build up voltage
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A 6 pole lap connected DC generator with 480 conductors has armature resistance of 0.06 Î©. If the conductors are reconnected to from a wave winding other things remaining unchanged, the value of armature resistance will be
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A lap wound 4 pole dc motor has 460 conductors. Find the number of parallel paths between the conductors?
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Series booster is a
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The power flow of a dc motor, with respect to a DC generator is
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In shunt dc motor the direction of rotation of the motor will reversed. When
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Armature reaction in dc motor results
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The armature reaction mmf in a DC machines has a form of
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In a 12 pole triplex lap wound DC armature, each conductor can carry current of 100 A. The rated current of this armature is
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The armature core of the rotor bars of dc motors are laminated
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A 4 pole dc motor with armature winding resistance of 0.6 ohm receives a supply of 230 Volt. If the back emf produced during running condition is equal to 210 volt. Calculate the current flowing through the armature at this point.
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In a 6 pole DC machine, 90 mechanical degrees correspond to which of the following electrical degree?
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A frog leg winding is used in a DC machine to eliminate
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Two generators G_{1} and G_{2} are to be operated in parallel to deliver a total current of 60 A. Generator one has a terminal voltage of 280 V on no load and 240 V when supplying 40 A current. Similarly the second generator has a voltage of 300 V when on no load and 240 V when supplying of 50 A of current. The output voltage of each generator will be
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The armature resistance of the dc motor is generally of the range
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The coil spam
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A 4 pole DC generator runs at 750 rpm and generate an emf of 240 V. The armature is wave wound and has 792 conductors. If the total flux from each pole is 0.0145 Wb. What is the leakage coefficient?
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Compensating winding are used to rectify the flux density waveform at
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If residual magnetism of a shunt generator is destroyed accidentally it may be restored by connecting its shunt field
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Two DC generators having equal opencircuit emfs but slight different load characteristics are operating in parallel, then
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In above question, the output power delivered by generator G_{1} and G_{2} will be
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The back emf produced in a dc motor depends on
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