[RicoElectrico]

> The second disadvantage is a lower efficiency than with permanent magnets, which cannot be improved so much as to match PM motors, because the electrical currents that circulate through the rotor windings must generate heat. The lower efficiency also makes cooling more difficult.

Wouldn't the back EMF help here? In brushed DC motor it surely does, reducing losses way below what full voltage over winding resistance would incur.

[cbolton]

That just means lower net voltage => lower current => lower torque right? When you do need torque you need current and the losses that come with it.