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If the supply frequency of a 6-pole synchronous motor is changed from 50 Hz to 60 Hz, then the speed regulation of a synchronous motor will be
- a)zero
- b)5%
- c)17%
- d)20%
Correct answer is option 'A'. Can you explain this answer?
Most Upvoted Answer
If the supply frequency of a 6-pole synchronous motor is changed from...
Speed regulation is defined as the change in speed of motor from no load to full load. A synchronous motor always runs on synchronous speed. For all frequencies, the speed of a synchronous motor remains same from no load to full load. Hence, for all supply frequencies, the speed regulation of a synchronous motor is always zero.
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If the supply frequency of a 6-pole synchronous motor is changed from...
Understanding Synchronous Motor Speed Regulation
When analyzing the speed regulation of a synchronous motor, it's essential to understand how the supply frequency and the number of poles influence its synchronous speed.
Key Concepts of Synchronous Speed
- Synchronous Speed Formula: The synchronous speed (Ns) of a motor is given by the formula:
Ns = (120 × Frequency) / Number of Poles
- For a 6-Pole Motor:
- At 50 Hz: Ns = (120 × 50) / 6 = 1000 RPM
- At 60 Hz: Ns = (120 × 60) / 6 = 1200 RPM
Impact of Frequency Change
- Constant Load Condition: When the frequency is changed from 50 Hz to 60 Hz, the synchronous speed increases from 1000 RPM to 1200 RPM. However, the synchronous motor operates at its synchronous speed without slipping, meaning it will adjust to the new speed based on the supply frequency.
- Zero Speed Regulation: Since the synchronous motor runs at synchronous speed and will change its speed immediately with an increase in supply frequency, it exhibits zero speed regulation. This means that regardless of the load, the speed remains constant at the synchronous speed determined by the frequency and number of poles.
Conclusion
- Correct Answer: The speed regulation of a synchronous motor when the supply frequency is changed from 50 Hz to 60 Hz is indeed zero (Option A), as the motor’s speed adjusts immediately to the new operating conditions without any fluctuation or slip.
When analyzing the speed regulation of a synchronous motor, it's essential to understand how the supply frequency and the number of poles influence its synchronous speed.
Key Concepts of Synchronous Speed
- Synchronous Speed Formula: The synchronous speed (Ns) of a motor is given by the formula:
Ns = (120 × Frequency) / Number of Poles
- For a 6-Pole Motor:
- At 50 Hz: Ns = (120 × 50) / 6 = 1000 RPM
- At 60 Hz: Ns = (120 × 60) / 6 = 1200 RPM
Impact of Frequency Change
- Constant Load Condition: When the frequency is changed from 50 Hz to 60 Hz, the synchronous speed increases from 1000 RPM to 1200 RPM. However, the synchronous motor operates at its synchronous speed without slipping, meaning it will adjust to the new speed based on the supply frequency.
- Zero Speed Regulation: Since the synchronous motor runs at synchronous speed and will change its speed immediately with an increase in supply frequency, it exhibits zero speed regulation. This means that regardless of the load, the speed remains constant at the synchronous speed determined by the frequency and number of poles.
Conclusion
- Correct Answer: The speed regulation of a synchronous motor when the supply frequency is changed from 50 Hz to 60 Hz is indeed zero (Option A), as the motor’s speed adjusts immediately to the new operating conditions without any fluctuation or slip.
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