What is the synchronous speed of a four pole motor compared to a two pole motor?

To understand the relationship between the synchronous speeds of a four-pole motor and a two-pole motor, it's key to consider how synchronous speed is calculated. Synchronous speed (in RPM) is determined by the formula:

[ \text{Synchronous Speed} = \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}} ]

For a two-pole motor, plugging in the number of poles gives you a synchronous speed that is directly related to the frequency of the electrical supply. Since it has fewer poles, it can achieve a higher speed.

On the other hand, a four-pole motor, having more poles, will have a lower synchronous speed because it takes more time to complete one cycle due to the additional poles. Specifically, when you apply the formula, a four-pole motor will have a synchronous speed that is half of what a two-pole motor would have if they are operating at the same frequency.

This means if you were to compare the synchronous speeds of both motors, you would find that the four-pole motor indeed runs at half the speed of the two-pole motor. Thus, this understanding fully corroborates the choice of it being half the speed of a two-p