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DC motor rotor arrangements

I know of two ways to arrange a three-phase DC motor armature with respect to the magnets: one is the normal one seen in toy motors, where there are three armature poles for every two magnets; the other is fairly common in RC brushless "outrunner" motors (and possibly in DC brushless motors in general), here there are three armature poles for every four magnets.

Does anyone know if these arrangements have NAMES in academic or commercial circles? Meaning, if I asked a motor designer what they were, what names would I get back?

TIA

Reply to
Tim Wescott
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A book on main US electrical standards called the NEC (2014) edition has a section called article 430. It provides the requirements for electric motors, motor circuits, and controllers.

Reply to
mogulah

Well, first, there is no such thing as a 3-phase DC permanent magnet motor. The toy motors you mention would be a 2-pole permanent magnet motor with 3 armature poles. These are simple PM DC commutator motors.

Now, when you get to brushless, the only motors that can be called "DC brushless" have electronic commutation circuits built inside the motor. Motors that use external commutation are AC synchronous PM motors, and are now used a LOT in all sorts of machinery. Hopefully, all this AC brushless vs. DC brushless nomenclature has finally settled out, as there used to be a lot of confusion over this.

So, brushless motors with external commutation should be called PM synchronous motors. Further classification is to whether the windings are optimized for trapezoidal or sinusoidal commutation.

I think most motor manufacturers have now come around to these designations, after about 20 years of conflicting naming.

Jon

Reply to
Jon Elson

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