Voltage Regulation of alternators
The voltage regulation of an alternator is defined as the change in terminal voltage from no-load to full-load (the speed and field excitation being constant) divided by full-load voltage.
Note that E0 - V is the arithmetic difference and not the phasor difference. The factors affecting the voltage regulation of an alternator are:
(i) IaRa drop in armature winding
(ii) IaXL drop in armature winding
(iii) Voltage change due to armature reaction
We have seen that change in terminal voltage due to armature reaction depends upon the armature current as well as power-factor of the load. For leading load p.f., the no-load voltage is less than the full-load voltage. Hence voltage regulation is negative in this case. The effects of different load power factors on the change in the terminal voltage with changes of load on the alternator are shown in Fig. Since the regulation of an alternator depends on the load and the load power factor, it is necessary to mention power factor while expressing regulation.