A permanent magnet DC (PMDC) motor consists of a permanent magnet stator and armature windings in the rotor. The armature winding is supplied with a DC voltage that causes a DC current to flow in the windings. Interaction between the magnetic field produced by the armature current and that of the permanent magnet stator causes the rotor to rotate. The following schematic shows a Permanent Magnet DC Motor Equivalent Circuit Diagram.
The above circuit includes the resistance Ra and inductance La of the motor’s armature windings. When a DC supply voltage Va is applied to the armature, current ia flows in the armature and the motor torque to balance the load torque. Due to the movement of the armature in the magnetic field a back-emf voltage eg is generated. The back-emf voltage opposes the voltage applied to the motor terminal and is proportional to the speed of the motor.
Get detail information of Permanent Magnet DC Motor Equivalent Circuit Diagram here:
DC Motor Drive – Link (source: www.ece.osu.edu)
Elementary Theory of DC Permanent Magnet Motors – Link (source: www.rci.rutgers.edu)