DC Electric Machines

The DC motor, whose basic principle is shown in Fig. 5.2, represents the simplest typology of electric machine, widely used for many domestic and industrial applications. 

Classic brushed DC motors present limitations due to the need for brushes to press against the collector, with the consequence of friction resistance. At higher 

In separately excited DC machines (Fig. 5.3d) the excitation is obtained by means of field windings which have a supply separated from the rotor windings, and this gives a separated control of speed and torque, according to what is required in an electric vehicle. Separately excited brushed DC motors were widely 

The DC motor is still used for some specific traction applications, but has been almost completely substituted by other types of motors, which are becoming more common for the electric vehicles. 

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The DC rotor winding is supplied with an external DC voltage by means of a brush-ring system, similar to the brush-collector system for the DC electric machine. The excitation of the rotor winding can also be obtained with a DC generator, known as exciter, located on the rotating shaft, or other excitation systems using AC exciter and solid state rectifiers. 

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