The D.c. Decay Test for Determining Synchronous Machine Parameters: Measurement and Simulation

The d.c. flux decay test has been proposed as an alternative and attractive method of extracting synchronous machine parameters. With the machine stationary, direct current is passed through two phases and the decay of current is observed following the short-circuiting of the supply. Tests on two large turbinegenerators have been performed and simulated by finite element electromagnetic calculations. The combination of tests, calculations and analysis has enabled the cause of various difficulties associated with the test to be isolated. Recommendations are made to improve the accuracy of measurements.