DC Machines

A DC machine has a field (stator poles or permanent magnets) and an armature (rotor) connected through a commutator and brushes, which reverse the coil current every half turn so torque stays in one direction.

$E = \frac{P\Phi N Z}{60 A} \qquad T = \frac{P\Phi Z I_a}{2\pi A}$

($P$ poles, $Z$ conductors, $A$ parallel paths, $N$ in rpm.) In short, $E = k\Phi\omega$ and $T = k\Phi I_a$.

Field connections: separately excited, shunt, series and compound.