D.C. machines are the electro mechanical energy converters which work from a d.c.
source and generate mechanical power or convert mechanical power into a d.c. power. These
machines can be broadly classified into two types, on the basis of their magnetic structure.
They are,
1. Homopolar machines
2. Heteropolar machines.

This application serves to both engineering students and professionals.

Any machine which involves DC current is called a DC machines. There are DC generators and DC motors.

DC generators produce DC current with a mechanical input.
DC motors generate a mechanical output with DC current as input.
The constructional feature of motors and generators are the same, it just depends on what is the input given.

The action of the commutator is to produce a fixed spatial distribution of current directions in the armature conductors independent of shaft rotation. The field created by these currents (armature reaction) is horizontally directed and is represented by the space vector Ia. The field established by the excitation of the stator poles is directed along the vertical axis and is represented by the space vector λf. The electromagnetic torque may be expressed as Te = k( Ia xλf ) .