The subject of the identification of the equivalent circuit parameters of large synchronous generators is revisited. The equivalent circuit of Park is used. On-line measurements are used in a Kalman filter to estimate the machine parameters. The formulation is linear and the extended Kalman filter is not needed. The approach is similar to that of Harley (1992), but flux linkages are not used in the present formulation in the machine model vector. An example is shown for an actual machine in operation in the Southwest United States. A transition to real time data using synthetic synchronized measurements (e.g., from a phasor measurement unit) is proposed and demonstrated.