What permits the max power generation of a dc motor? Is it the max rpm's it can have? The length of copper wire in the motor? The strength of the magnet?

 

~EE

Two things come to my mind:

 

- magnetization saturation of iron (iron saturates at less than 2T, and we know nothing better at the same price magnitude level)

- specific resistance of copper (funny, copper has such a small resistance but still we could much benefit from reducing it further)

 

But many other things can help: insulation strength improvement, cooling improvements, hysteresis and eddy current reduction, commutator design (if it exists), tighter manufacturing tolerances...

 

(And when we know no better, we just increase the motor size.)

For a DC motor of given W or kW size, it's much a matter of acceptable losses.

 

In the MW size, the flux created by the rotor, and the difficulty to compensate it exactly with the special stator winding, is one limit.

 

If present, the commutator is always a limit at any size: look at a car starter, which accepts big losses for a short time to produce much power in a small volume and mass. Its commutator is huge as compared with the magnetic circuit.

 

When designing a DC machine, the commutator gets impractical or a huge drawback over few MW. At higher power, machines use to be three-phase, and if needed (say, to vary the speed), they have power electronics.

Two things come to my mind:

 

- magnetization saturation of iron (iron saturates at less than 2T, and we know nothing better at the same price magnitude level)

- specific resistance of copper (funny, copper has such a small resistance but still we could much benefit from reducing it further)

 

But many other things can help: insulation strength improvement, cooling improvements, hysteresis and eddy current reduction, commutator design (if it exists), tighter manufacturing tolerances...

 

(And when we know no better, we just increase the motor size.)

Resistance of copper is about 0.0175 Ohm's at 15°C. Ofcourse depending on the width and lenght

the bigger the size the bigger the armature reaction so you can't forget to compensate that by also adding compensation conductors where the current flows in the opposite direction and poles on the side which push the pole axis and zero axis back in it's place. This will be one expesive generator/motor.