Electrical Machines Objective Questions
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In a DC machine, which of these parameters remain the same whether it runs as a DC motor or a DC generator?
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Addition of 0.3 % to 4.5 % silicon to iron
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The two windings of a transformer have an inductor of 2 H each. If mutual inductor between them is also 2 H, then
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When an electric train is moving down a hill, the DC motor will operate as
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A shunt generator has a critical field resistance of 300 Î© at a speed of 800 rpm if the speed is raised to 1000 rpm the critical field resistance is
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In DC generator, the electricity produced in armature is
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For high current and low current rating which winding is employed to DC machine?
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Addition of 0.3 % to 4.5 % silicon to iron
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Commutators in DC machines have a role of which converts
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If direct axis reactance X_{d} and quadrature axis reactance X_{q} are equal, then reluctance power is
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The polarity of a DC generator can be reversed by
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Hysteresis loss is proportional to
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An 8 pole DC generator has 500 armature conductors and useful per pole of 0.065 Wb what will be the emf generated if it is lap connected and runs at 1000 rpm. What must be the speed at which it is driven to produce the same emf if it is wave wound?
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A 4 pole dynamo with wave wound armature has 51 slots contains 20 conductors in each slot. If induced emf 357 Volts and speed is 8500 rpm, flux per pole will be
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DC machine is a
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Generators works on the principle of production
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A 2 pole synchronous machine is operating at 3000 rpm. Find the relation between electrical angular momentum (Ï‰_{e}) and mechanical angular momentum (Ï‰_{m}) ?
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A laminated iron core has reduced eddy current losses because
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Which machine is used for battery charging?
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E_{g} ( generated emf ) and E_{b} ( back emf ) both are
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What is the full form of MNP?
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Emf induced in a coil rotating in a uniform magnetic field will be maximum when the
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For low current and high voltage rating which winding is employed to DC machine?
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A lap wound DC machine has 400 conductors and 8 poles. The voltage induced per conductor is 2 volts. The machine generates a voltage of
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The DC generator runs at a speed of 1000 rpm and flux per pole is 0.2 Wb, number of poles are 2 the winding is wave wound and having 480 conductors. The critical speed is 1200 rpm. Then the generated emf ( E_{g} )
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The principle of dynamically induced emf is utilized in
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Magnetic field in a DC generator is produced by
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The torque speed characteristics of a AC servomotor is approximately
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Armature reaction in DC generators will results in
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A synchronous machine has P number of poles, find the relation between electrical angular momentum (Ï‰_{e}) and mechanical angular momentum (Ï‰_{m})?
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