What is the synchronous speed formula for single-phase motors?

The synchronous speed formula for single-phase motors is determined by taking into account the electrical frequency and the number of poles within the motor. The correct formula is based on the principle that synchronous speed is the speed at which the magnetic field rotates and is necessary for the efficient operation of the motor.

In this context, the formula that accurately captures this relationship is derived from the fundamental concepts of alternating current (AC) motor operation. The synchronous speed in revolutions per minute (RPM) is calculated using the formula:

Synchronous speed (RPM) = (120 × frequency) / number of poles.

The factor of 120 arises from the fact that there are 120 seconds in two minutes (since we want RPM, which is a measure of speed over time) and because the alternating current cycles through phases that relate to the poles in the motor.

Choosing this formula reflects an understanding of how many electrical cycles occur per minute and how they relate to the mechanical design of the motor, specifically its pole count. This is why the synchronous speed calculation is crucial for determining the operational capabilities of single-phase motors, as it helps in assessing their efficiency and compatibility with specific applications.