Page 619 - Basic Electrical Engineering

Z is the total number of armature conductors and they are connected in A
number of parallel paths. The total number of conductors per parallel path

would be equal to .

The induced EMF available across the output terminals will be equal to the
induced EMF per parallel path.
Thus the total induced EMF, E is

or,

When the dc machine is also working as a motor, the current-carrying
conductors placed in the magnetic field will develop torque and rotate in a
particular direction. When they would rotate, EMF will also be induced in

them.
The equation for induced EMF will be the same both in generating and

motoring mode of operation of the machine. The induced EMF in the
armature of a dc motor is often called back EMF as it opposes the applied
voltage.

7.4 TYPES OF DC MACHINES
In the dc generator shown in Fig. 7.11, the armature has to be rotated by

some prime mover and the field windings have to be excited by giving a dc
supply to them. We, therefore, would need a separate dc source of supply for