Finite element analysis of electrical machines used in two-frequency indirect temperature rise tests

Abstract

Heat runs of large asynchronous machines (AM) are hardly ever conducted under load but with synthetic approaches, such as the two-frequency method. In its classical variant, the AM’s stator is fed by two series-connected synchronous machines (SM) with different frequencies, for instance 50 and 40 Hz. While the 50 Hz voltage determines the AM’s flux, the 40 Hz source causes an AM stator current close to its rated value. Together, voltage and current yield approximately full load losses in the AM without mechanical loading. For designing the amortisseurs of the synchronous generators, damper losses were calculated using the Finite Element method. Additionally, calculated full load AM losses were compared against their respective values for the two-frequency method.