When discussing how many poles a brushless electric motor has, we are referring to the number of magnetic poles built into the motor’s rotor. Motor pole count is an important—yet often misunderstood—design variable that directly affects motor behavior, including Kv, torque characteristics, efficiency, and cogging behavior.
This article focuses primarily on brushless inrunner motors, where the rotor spins inside the stator. While outrunner motors are mentioned briefly for comparison, the core discussion applies to inrunners, which are common in higher-RPM and higher-speed RC applications.
Common Pole Counts in Brushless Motors
Most inrunner brushless motors fall into one of the following categories:
- 2-pole motors (common)
- 4-pole motors (more common)
- 6-pole motors (less common, but available)
In contrast, outrunner motors frequently use much higher pole counts, often exceeding 6 poles. This difference in construction is one of the reasons outrunners naturally produce higher torque at lower RPM.
(If you haven’t already, it’s worth reading a dedicated comparison on inrunner vs outrunner motors, as the differences go well beyond pole count alone.)
Motor Pole Count vs Motor Characteristics
When all other variables are held constant—physical motor size, winding style, and materials—the most noticeable effect of increasing pole count is a reduction in Kv.
Why does this happen?
- Kv is defined as RPM per volt
- Increasing the number of magnetic poles increases the number of magnetic interactions per electrical cycle
- More interactions per cycle means lower RPM for the same applied voltage
👉 Key takeaway:
If two motors are identical in size and construction, the motor with more poles will have a lower Kv.
This single change cascades into nearly every other performance difference associated with pole count.
How Pole Count Affects Cogging Torque
Cogging torque is another area where pole count plays a role—particularly in slotted stator motors, which are common in RC brushless designs.
As a general rule for inrunner motors:
- Increasing pole count increases cogging torque
This happens because:
- More poles interact with stator slots more frequently
- The magnetic “detent” effect becomes stronger
In many RC airplane applications, cogging is not a major concern because motors operate at speed once airborne. However, in applications requiring smooth low-RPM operation, increased cogging can become noticeable.
What Does a Drop in Kv Actually Do?
When Kv drops while physical motor size and winding count remain constant, torque increases.
Why?
- Lower Kv motors produce more torque per amp
- Torque is inversely related to Kv when other variables are fixed
Practical implications:
- More torque can improve acceleration
- Lower Kv limits maximum achievable RPM
- Power delivery becomes more “torque-biased” rather than speed-biased
Whether this is an advantage or disadvantage depends entirely on the application:
- High-speed setups often favor higher Kv
- Heavier or more aggressively loaded setups benefit from torque
How Manufacturers Maintain a Usable Kv
If higher pole count naturally lowers Kv, how do manufacturers prevent the motor from becoming unusably slow?
The most common solution is to reduce the number of windings in the motor.
Example: 2-Pole vs 4-Pole Motors
- A 2-pole motor typically uses more windings
- A 4-pole motor uses fewer windings to raise Kv back to a practical range
However, removing windings creates unused physical space inside the motor.
The solution: more copper
Manufacturers compensate by:
- Using thicker wire (lower gauge number)
- Increasing copper fill within the stator slots
From basic electrical theory:
- Increasing conductor cross-section reduces resistance
- Lower resistance allows higher current flow
- Higher current capability increases power handling
Advantages and Disadvantages of Higher Pole Count Motors
Advantages (when Kv and size are equal)
When comparing a 4-pole motor and a 2-pole motor of the same:
- physical size
- Kv rating
…the 4-pole motor will typically:
- Handle higher current
- Produce more power
- Operate with better efficiency under load
This is why higher-pole motors are often favored in high-power applications.
Disadvantages and Limitations
Despite the benefits, higher pole count motors also have tradeoffs:
1. Fewer available Kv options
- 2-pole motors are produced in a wider range of Kv values
- 4-pole motors may limit fine-tuning for specific setups
2. Winding configuration complexity
Brushless motors can use different termination styles:
- Delta (Δ) wind
- Wye (Y) wind
Each winding style alters:
- effective Kv
- torque curve
- current draw
While this provides flexibility, it also adds complexity and can make it harder to find an exact match for a specific application.
Which Pole Count Is Best for You?
There is no universal “best” pole count.
In many real-world RC setups:
- The performance differences may be subtle, and is more dependent on design
- Pilot/Driver style, gearing, prop selection, and ESC tuning can overshadow pole count differences
Best recommendation:
My best recommendation is to select a motor based on power potential and Kv. Don’t look at and select a motor based off of pole counts. It’s really that simple and it also makes it easier for you to select a motor as we take one of the many variables right out of the equation!
Final Thoughts
Motor pole count influences Kv, torque, current handling, efficiency, and cogging behavior, but it is only one variable in a much larger system.
Understanding these relationships allows you to make better motor choices—not by guessing, but by knowing why a motor behaves the way it does. Select a motor based on power, performance and Kv, not by pole count.