VOLTAGE REGULATION OF THE ALTERNATOR. I2/ 



point on one of the curves represents a given current output per 

 phase, and the ordinate of the point represents the terminal volt- 

 age observed when the given current output is reduced to zero, 

 the field current having been adjusted to give the rated voltage 

 of 2400 volts with the given current output. Thus when the 

 field excitation is adjusted to give 2400 volts across the terminals 

 of the alternator with full-load current output of 28. 1 amperes 

 per phase, and unity power factor, the terminal voltage rises to 

 2625 volts at zero load. That is, the full-load regulation of the 

 machine with unity power factor is (2625 2400) --2400= 0.094 



or 9.4 per cent. With half-load current of 14.05 amperes per 

 phase and unity power factor, the terminal voltage rises from 

 2400 volts at half-load to 2450 volts at zero load. That is, the 

 half-load regulation of the machine with unity power factor is 

 (2450 2400) -r- 2400 = 0.021 or 2.1 per cent. With a power 

 factor of 0.70 the full-load regulation is 22.5 per cent, and the 

 half-load regulation is 10.0 per cent. 



63. Theory of voltage regulation of the alternator. The decrease 

 of terminal voltage of an alternator with increase of current out- 

 put is due to two effects, namely, (a) the resistance of the arma- 

 ture windings, and (U) the magnetizing action of the armature 

 current or currents. In discussing the effect of magnetizing 



