I know that current brushless motors, have a non rotating core made of copper coils, with permanent magnets on the outside rotating around it, and eventually connected to a shaft. But i was wondering, if it was possible to make the exact opposite ?

I mean having a rotating core made of magnets around a shaft, with non rotating coils around it. Would it work? Hallback arrays of magnets would still work ?

I mean, phases are the same, and Magnetic field are not unidirectional. I don't see why it couldn't.

Thank you in advance.


1 Answer 1


One reason you might not be able to envision why it doesn't work is because it does. There are compromises with respect to torque and motor size, but what you're describing is called an inrunner motor.

From the linked site:

The permanent magnets on the outrunner are placed on the rotor and the rotor spins on the outside case. On the inside of the motor are the stator windings which do not rotate, they are fixed in position.


On the inrunner motor, you essentially have the complete opposite true for how it is built. On the outer side of the motor is the case. The case in this situation does not rotate and is fixed. The stator windings are placed on the inside face of the case. When you spin the motor shaft of an inrunner, you are spinning the rotor which also contains the permanent magnets much like the outrunner. The difference of course being that they are now at the center of the motor.

It's the first time I've attempted to validate what I believe and it's good to see this confirmation.

  • $\begingroup$ Thank you so much for this piece of information. Thats exactly what i was looking for and I'm glad all of this is possible. Much love $\endgroup$
    – ElBigZob
    Oct 2, 2020 at 14:45

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