Permanent Magnet DC Motor

There are four main types of DC motor, namely permanent magnet, series, shunt and separately excited. The latter three all use field coils in the stator (the part which doesn't move) to generate a magnetic field for the rotor to spin in, and their name simply refers to the way the field coils are wired with respect to the rotor coils. All four types use a commutator to control which rotor coils are energised at any given time in order to maintain rotation, and it is enough just to apply a DC voltage across their terminals to get the motor to spin, so they are relatively easy to control.