Video: DC Motor Basics

DC motor speed is pretty much universally limited by mechanical considerations: the commutators bounce, the bearings wear out, and when you solve those problems and push it faster, the armature flies apart from centripetal acceleration.

If you're looking at the data sheets for motors to get the maximum speed, and then computing your limit from that, then the relationship between maximum speed and anything that the free electrons in the winding are doing is purely serendipitous.

could be the direction of the solar wind at full moon that determines it

more likely it is the point where friction and torque is equal

Generally I think the short-duration limit is set by shaft whirl. That's the picturesque name for what happens when the rotation rate equals the frequency of the lowest-order bending mode of the shaft + armature. Things tend to get very exciting right around there.

Cheers

Phil Hobbs

Hi Tim, My goal is not to go so fast that the motor almost flies apart. A low current in a motor will make it go slow, not just because of friction, because of the electron velocity being the determining factor in magnetic motor speed. Even with no friction, a low current cannot spin the motor faster than 795,000 times as fast as the average electron velocity. If the motor is forced to go faster, it is called a Generator. Then electrons are pushed backwards in the copper wire. Relative velocity is the foundation of DC motor motion.

what?

Oh, good grief.

You need to go back to Area 51 and brush up on anti-gravitational physics

Are you talking about the thermal velocity of the electrons or the drift velocity? (when they are in an E-Field) (Does your "theory" motor spin faster or slower at low temperatures?)

George H.

I guess FAKE NEWS isn't all we have these days,.

Jamie

The drift velocity is the velocity I called the average velocity. The electric field makes a current flow as if small particles were free to drift in a copper wire. That average velocity is much slower than the orthogonal speed of the motor's rotor. The motor depends on electron motion to provide magnetism. For a frictionless motor, the temperature does not matter. I am theorizing that the motor has a maximum speed, relative to the electron drift velocity. Not the speed at destruction, a slow speed of motor rotation is always less than 795,000 times faster than the electron drift velocity. If the motor is forced to go faster than that by an outside force, the motor becomes a generator.

"Alwys 795,000 times slower than he electron drift velocity". That is a slow speed, indeed.

You should stop theorizing and learn.