Voltage-excitation characteristics of synchronous machines

The voltage-excitation characteristics of synchronous machines may be calculated by either cylindrical-rotor or two-axis theory and in each case saturation effects may or may not be included. In order to evaluate the extent to which these methods are applicable to specific cases, six machines are considered¿three turbo-alternators and three salient-pole alternators¿covering a range of synchronous reactances from 0.7 p.u. to 1.75 p.u. and a range of saturation factors from 1.6 to 2.2. The errors involved in the use of the various methods are evaluated, and recommendations are made concerning the most suitable methods for calculating these voltage-excitation characteristics.