Do motors that are supplied with a DC Voltage need either brushed or electronic commutation?  Does a motor exist whereby a constant DC supply voltage will rotate a motor, without commutation?

Research "Homopolar" motors. They do not require commutation. They do however require brushes. YouTube has many novelty homopolar motors. The Navy is supposed to be researching the use of a superconducting homopolar motor.

Hi Clyde, there are some kind of Homopolars that don't need burshes. They have DC winding and also three phase winding on the stator. The DC winding provides the excitation for the motor. There are only salient poles on the rotor with no winding or PM. The "homopolar" motors on the YouTube are certain kind of outer rotor brushed DC motor with the same working principle and similar structures.

Hi Xikai,
Good Point! I'm glad you brought this up. I didn't mean to be misleading by not including this fact, I was just addressing Peter's reference to commutation.