What is the relation between maximum power and the number of poles?

The relationship between maximum power and the number of poles in an electric machine (such as an electric motor or generator) is directly related to the speed at which the machine operates and indirectly linked to its physical size and thermal management aspects. Here’s a breakdown of how they are related:

1. Speed and Frequency Relation: In electric machines, the speed at which the machine operates is inversely proportional to the number of poles. This is described by the formula: Speed (N) = 120f / P, where ‘N’ is the speed in revolutions per minute (RPM), ‘f’ is the frequency of the electrical supply in hertz, and ‘P’ is the number of poles. As the number of poles increases, the speed of the machine decreases.

2. Maximum Power and Speed: The maximum power that an electric machine can generate or handle is partly determined by its operating speed. For a given power output, a machine with more poles (and thus operating at a lower speed) will need to be physically larger than a machine with fewer poles, to accommodate the lower speed at the same power level. This is because the torque required to produce the same power increases as the speed decreases (since power is the product of torque and speed).

3. Thermal Considerations: Larger machines (those with more poles and hence lower speeds for the same power output) have a larger surface area, which potentially improves their ability to dissipate heat, a critical aspect in determining