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.