Losses in an AC Generator:

The load current flows by the armature in all AC generators.  Such as any coil, the armature has a few amount of resistance and inductive reactance. A combination of these make up what is understand as the internal resistance, that causes a loss in an AC generator. Whenever the load current flows, a voltage drop is established across the internal resistance. That voltage drop subtracts from the outcome voltage and, therefore, represents produced voltage and power which is lost and not available to the load.   A voltage drop in an AC generator could be found using Equation (10-2).

Voltage drop =  I_aR_a +  I_aX_La                                                       (10-2)

where

I_a = armature current armature resistance

R_a = armature inductive reactance

X_La = Hysteresis Losses

Hysteresis  losses  occur  whenever  iron  cores  within  an  AC  generator  are  subject  to  effects  from  a magnetic field. A magnetic domains of the cores are held in alignment within the field in varying numbers which is dependent upon field strength. The magnetic domains rotate, along with respect to the domains not held in alignment, one full turn during every rotation of the rotor. That rotation of magnetic domains in the iron causes friction and heat.   The heat generates through this friction is known as magnetic hysteresis loss.

To decrease hysteresis losses, most AC armatures are constructed of heat-treated silicon steel, that has an inherently low hysteresis loss.A laminations are heated to a dull red and then allowed to cool after the heat-treated silicon steel is formed to the desired shape.  This procedure, known as annealing, reduces hysteresis losses to a extremely low value.