Q-43: What is the significance of the “number of turns” with respect to electric motors?
A-43: I asked my flying partner and probably one of the best electric motor experts in the country, Tom Hunt, to give me his thoughts on this question. In Tom’s words: "Different motor manufacturers unfortunately use different designations to identify their products. For instance, a Mega 22/30/3 is brushless motor that has a 22 mm-diameter case x 30-mm-long rotor, and a three-turn stator.
"An AXI 2208/26 is similar and has a 22-mm-diameter case x 8 mm-long rotor
and a 26-turn stator. An Aveox 27/13/3 seems to use the following: 27-mm
diameter of the outside of the motor (not the rotor!) and 13 mm is the length of
the rotor while three is the number of turns of the stator. Other manufacturers
of brushless motors such as Cermark, Nippy, and PJS do not describe their motor
dimensions in the nomenclature. A Hacker B20-26S is 20 mm in diameter, with the
“S” indicating short length (L is for long) and is a 26-turn stator.
"Turns are much like gearing! The higher the number of turns, the larger the
propeller you can swing, however, the lower the maximum current it can
withstand. Brushless motors that come in 1-, 2-, 3-, 4-, and 5-turn varieties
are usually the internal-rotor type (but not always like the Hacker!). Brushless
motors with high numbers of turns (say 10-30) are usually the external rotor (outrunner
as we call it) type like AXI, Nippy, PJS, and the new little Hacker Baby."