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A synchronous motor is operating on no-load at unity power factor. If the field current is increased, the pf will become
- a)leading and the current will increase.
- b)lagging and the current will decrease.
- c)leading and the current will decrease.
- d)lagging and the current will increase.
Correct answer is option 'A'. Can you explain this answer?
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Verified Answer
A synchronous motor is operating on no-load at unity power factor. If ...
Motor becomes over-excited and starts operating at leading pf with the increase in field current.
Here, Ia will increase.
Here, Ia will increase.
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A synchronous motor is operating on no-load at unity power factor. If ...
No-Load Operation of Synchronous Motor at Unity Power Factor
When a synchronous motor is operating on no-load, it means that there is no mechanical load connected to the motor shaft. In this condition, the motor is only required to overcome the core losses and frictional losses, resulting in a very small power requirement.
At unity power factor, the current drawn by the synchronous motor is in phase with the voltage. This means that the current waveform is in synchronization with the voltage waveform, resulting in a power factor of 1.
Effect of Increasing Field Current
When the field current of a synchronous motor is increased, it affects the power factor and current drawn by the motor. Let's analyze the effect of increasing the field current:
1. Power Factor:
- When the field current is increased, the magnetic field produced by the field winding becomes stronger.
- As a result, the synchronous motor tends to operate with a leading power factor.
- This is because the stronger magnetic field helps to magnetize the rotor winding, allowing it to generate a magnetic field that leads the stator magnetic field.
- Therefore, the power factor of the synchronous motor increases and becomes leading.
2. Current:
- As the field current is increased, the magnetic field strength increases, which in turn increases the torque developed by the motor.
- However, since the motor is operating at no-load, the increase in torque does not result in an increase in current drawn by the motor.
- In fact, the current drawn by the motor may decrease slightly due to the improved power factor.
Conclusion
Based on the above analysis, when the field current of a synchronous motor operating on no-load at unity power factor is increased, the power factor becomes leading and the current may slightly decrease. Therefore, the correct answer is option 'A' - leading and the current will increase.
When a synchronous motor is operating on no-load, it means that there is no mechanical load connected to the motor shaft. In this condition, the motor is only required to overcome the core losses and frictional losses, resulting in a very small power requirement.
At unity power factor, the current drawn by the synchronous motor is in phase with the voltage. This means that the current waveform is in synchronization with the voltage waveform, resulting in a power factor of 1.
Effect of Increasing Field Current
When the field current of a synchronous motor is increased, it affects the power factor and current drawn by the motor. Let's analyze the effect of increasing the field current:
1. Power Factor:
- When the field current is increased, the magnetic field produced by the field winding becomes stronger.
- As a result, the synchronous motor tends to operate with a leading power factor.
- This is because the stronger magnetic field helps to magnetize the rotor winding, allowing it to generate a magnetic field that leads the stator magnetic field.
- Therefore, the power factor of the synchronous motor increases and becomes leading.
2. Current:
- As the field current is increased, the magnetic field strength increases, which in turn increases the torque developed by the motor.
- However, since the motor is operating at no-load, the increase in torque does not result in an increase in current drawn by the motor.
- In fact, the current drawn by the motor may decrease slightly due to the improved power factor.
Conclusion
Based on the above analysis, when the field current of a synchronous motor operating on no-load at unity power factor is increased, the power factor becomes leading and the current may slightly decrease. Therefore, the correct answer is option 'A' - leading and the current will increase.
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A synchronous motor is operating on no-load at unity power factor. If the field current is increased, the pf will becomea)leading and the current will increase.b)lagging and the current will decrease.c)leading and the current will decrease.d)lagging and the current will increase.Correct answer is option 'A'. Can you explain this answer?
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A synchronous motor is operating on no-load at unity power factor. If the field current is increased, the pf will becomea)leading and the current will increase.b)lagging and the current will decrease.c)leading and the current will decrease.d)lagging and the current will increase.Correct answer is option 'A'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A synchronous motor is operating on no-load at unity power factor. If the field current is increased, the pf will becomea)leading and the current will increase.b)lagging and the current will decrease.c)leading and the current will decrease.d)lagging and the current will increase.Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A synchronous motor is operating on no-load at unity power factor. If the field current is increased, the pf will becomea)leading and the current will increase.b)lagging and the current will decrease.c)leading and the current will decrease.d)lagging and the current will increase.Correct answer is option 'A'. Can you explain this answer?.
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