Increasing the pole count can increase the torque capacity, under certain conditions. This happens thanks to the reduced flux per pole, allowing a thinner stator (or rotor) yoke. This can in turn translate to a larger airgap radius or/and deeper slots, both of which lead to increased torque.
The number of poles in a motor is the number of poles each motor contains per phase. And the poles of the motor appear in pairs, so the motor will have 2, 4, 6, 6 poles, etc.
The benefits of having a high number of poles
Usually, depending on the application, an increase in the number of poles in the motor provides some benefits.
- Higher Torque: Motors with more poles can produce higher torque than motors with fewer poles.
- Runs smoother: A motor with more poles also provides smoother operation.
- More efficient: The extra poles reduce the amount of power wasted in the form of heat, thus allowing the motor to convert more of the input power into mechanical energy, increasing motor efficiency.
However, there are some potential drawbacks to using multi-pole motors.
- Motors with more poles may also have higher inertia, which may make them harder to control and may shorten their response time.
- The electrical frequency of motors is proportional to the number of poles, so increasing the number of poles will increase the electrical frequency. The rapidly changing magnetic field induces large eddy currents in the stator core, which manifest themselves as power losses.
Therefore, whether a multi-pole motor is better depends on the specific application and its requirements. In general, motors with more poles are better suited for applications that require high torque, high efficiency, and smooth operation at low speeds, while motors with fewer poles may be better suited for applications that require high-speed operation or compact designs.