| 1. | The torque angle, in a synchronous motor, is the angle between ? | |
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the supply voltage and the back e.m.f.
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magnetising current and back e.m.f.
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the rotating stator flux and rotor poles
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none of the above
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Report Question| 2. | In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be ? | |
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3000 r.p.m.
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1500 r.p.m.
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750 r.p.m.
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none of the above
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| 3. | A synchronous machine with low value of short-circuit ratio has ? | |
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lower stability limit
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high stability limit
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good speed regulation
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good voltage regulation
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| 4. | For power factor correction, synchronous motors operate at ? | |
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load and greatly over-excited fields
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no-load and under-excited fields
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normal load with minimum excitation
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normal load with zero excitation
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| 5. | The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as ? | |
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locked-rotor torque
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synchronous torque
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pull up torque
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reluctance torque
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| 6. | In a synchronous motor, the forced vibrations will be maximum when driving ? | |
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a reciprocating air compressor
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a centrifugal pump
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a centrifugal blower
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any of the above
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| 7. | In a synchronous machine in case the axis of field flux is in line with the armature flux, then ? | |
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the machine is working as synchronous generator
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the machine is working as synchronous motor
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the machine will vibrate violently
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none of the above
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| 8. | The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as ? | |
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pull-up torque
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pull-in torque
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pull-out torque
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none of the above
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| 9. | The maximum value of torque that a synchronous motor can develop without losing its synchronism is known as ? | |
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slip torque
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pull-out torque
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breaking torque
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synchronising torque
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| 10. | A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have ? | |
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no change of power factor
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lagging power factor with over-excitation
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leading power factor with under excitation
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leading power factor with over-excitation
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