Capability Curves and Excitation Requirements of Saturated Cylindrical Rotor Synchronous Machines

Generator capability curves, used by operating personnel in the loading of generators, are usually based upon a generator synchronous reactance equal to 1/SCR. Use of this reactance partially corrects for the effects of saturation and, while resulting in a reactive capability in error by less than 1.3 percent, produces a field excitation requirement as much as 3.8 percent lower than actual requirements. The effect of saturation, expressed by the saturation factor K, and Kingsley´s equation for saturated synchronous reactance, results in capability curves and excitation requirements which agree with test data.