Open-circuit voltage decay of a turbogenerator

The decay of terminal voltage of an unexcited turbogenerator, following its disconnection from the a.c. busbars, is determined analytically. It is shown that, because of eddy current in the solid rotor, an infinite number of exponential-decay terms are required to describe the voltage decay. Results obtained theoretically are compared with those of tests carried out by the Central Electricity Generating Board at Northfleet, and good agreement is obtained. Of particular interest are the large quadrature-axis time constants evident in both theoretical and experimental studies.