How does a change in supply frequency affect a single-phase motor's speed?

How does a change in supply frequency affect a single-phase motor's speed?

• A. It decreases torque output
• B. It directly alters the synchronous speed
• C. It has no impact on speed
• D. It increases motor noise

Answer: (B)

A change in supply frequency directly alters the synchronous speed of a single-phase motor due to the relationship defined by the formula for synchronous speed, which is expressed in revolutions per minute (RPM) as: Synchronous Speed (RPM) = (120 x Frequency (Hz)) / Number of Poles As the supply frequency increases, the synchronous speed also increases, meaning the motor will run faster. Conversely, if the supply frequency decreases, the synchronous speed will decrease, resulting in slower motor operation. This relationship is crucial because it highlights how frequency adjustments provide control over motor speed in applications where varying speed is advantageous. Understanding this interaction is vital for those working with single-phase motors, as it allows for effective motor selection and application in various settings.

A change in supply frequency directly alters the synchronous speed of a single-phase motor due to the relationship defined by the formula for synchronous speed, which is expressed in revolutions per minute (RPM) as:

Synchronous Speed (RPM) = (120 x Frequency (Hz)) / Number of Poles

As the supply frequency increases, the synchronous speed also increases, meaning the motor will run faster. Conversely, if the supply frequency decreases, the synchronous speed will decrease, resulting in slower motor operation.

This relationship is crucial because it highlights how frequency adjustments provide control over motor speed in applications where varying speed is advantageous. Understanding this interaction is vital for those working with single-phase motors, as it allows for effective motor selection and application in various settings.