Electrical Machines Objective Questions
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The effect of  on main field flux is armature reaction?
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At slip s = 1 torque developed in machine is
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Two singlephase alternators operating in parallel have induced EMFs on open circuit of 230∠0° and 230∠10° volts and respective reactance of j2 Ω j3 Ω calculate the terminal voltage
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Why are capacitors used with large AC induction motor?
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Which of the following motor is used in grinders?
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Two singlephase alternators operating in parallel have induced EMFs on open circuit of 230∠0° and 230∠10° volts and respective reactance of j2 Ω j3 Ω calculate the terminal voltage, find the power delivered by each of the alternators to a load of impedance 6Ω(resistive)
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If the field current is reduced to zero the maximum power developed by alternator is
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What type of dielectric material is used in capacitors used for fans and for power factor correction?
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Type of single phase motor having highest power factor at full load is
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For a single phase capacitor start induction motor which of the following is valid?
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For the above problem, find the induced voltage of an alternator of it is to deliver a load of 100 A at power factor of 0.8 lagging with terminal voltage of 200 V.
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If dimension of all the parts of a synchorous generator and the number of field and armature turns are double, then generated voltage will change by a factor of
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Armature flux is.............with respect to main field flux or main field poles?
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A 3phase, alternator has generated emf per phase of 230 V with 10% 3rd harmonic and 6% 5th harmonic content, find rms line voltage for delta connection?
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A 3phase, alternator has generated emf per phase of 230 V with 10% 3rd harmonic and 6% 5th harmonic content. Calculate rms line voltage for star connection.
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Find the synchronous reactance of alternators in which a given field current of 200 A on short circuit and a generated emf of 50 V on open circuit. Armature resistance is 0.1 ohm
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What is/are the necessary conditions for voltage build up in self excited generator?
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A three phase induction motor has a synchronous speed of 1500 rpm the machine runs at 1460 rpm at a particular load. The slip at this load is ___________.
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Which of the following motor used in hair dryers?
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Slip speed is the
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Induction motors have the advantage of
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Which single phase motor is used for a refrigerator?
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Voltage across the open circuited field termninals of a synchorous machine under slip test is
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No load saturation characteristics are plotted between
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Two 3phase AC generators are such that one has twice the linear dimensions of the other. The field windings of each are excited to give identical sinusoidal airgap flux density waveform. Both have the same number of stator slots and identical winding patterns. The conductor/slot in a big generator is K times that of the smaller one. The value of K to get equal no load voltage at same frequency is
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Cross magnetization effects which of the following?
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Which motors are preferred for refrigeration and air conditioning in smaller units?
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Capacitor start capacitor run provides
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Torque angle of a synchorous machine operating from a constant voltage bus is usually defined as the space angle between
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Capacitor fitted with ceiling / table fans is of the value of
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