Determine number of motor poles

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The number of motor poles is an important characteristic of a gimbal motor, and frequently needs to be known to setup the STorM32 gimbal controller correctly.

Often there is confusion about it, because manufacturer/vendor information is unclear or not even available.

Fortunately, it is quite simple to determine this number. Two methods are:

  • The simplest method is visual inspection: Count the number of the magnets which are glued to the inner side of the rotor bell, and this is the number of motor poles.
  • Sometimes visual inspection is not possible, e.g., for motors with ferrite rings. In this case you have this simple option: Apply a small voltage to two phases of the motor (it does not matter which two out of the three phases you choose). Importantly: USE A SMALL VOLTAGE! It is sufficient to have a low current flowing, so try 1 V or 1.5 V, but not more (for a typical motor phase resistance of 10 Ohms a voltage of 1 V already implies a current of 100 mA). Now grab the rotor bell and turn it around by hand. You will feel that it snaps into certain positions. Count the number of positions it snaps into for a rotation by 360°. That is the number of motor pole pairs. Multiply by two and you get the number of motor poles.