Abstract: A method for detecting a fault in an AC/AC exciter having an exciter rotor and an exciter stator. A signal reflecting the current or voltage, is obtained at an exciter rotor winding or at an exciter stator winding. A frequency analysis is applied and on the basis of a presence of a frequency component, a rotor current or voltage signal, at a first frequency fs*(2?s), where fs is a supply frequency of the exciter stator and s is an exciter slip, it is determined whether the exciter suffers from an inter-turn short circuit in an exciter stator winding or not. On the basis of a presence of a frequency component, in the case of a stator current signal or a stator voltage signal, at a second frequency fs*(1?2*s), it is determined whether the exciter suffers from an inter-turn short circuit in an exciter rotor winding or not. Presence of frequency components at the first and/or second frequencies in windings of an AC/AC exciter indicate the mentioned fault conditions.

Abstract: A method for detecting a fault in an AC/AC exciter having an exciter rotor and an exciter stator. A signal reflecting the current or voltage, is obtained at an exciter rotor winding or at an exciter stator winding. A frequency analysis is applied and on the basis of a presence of a frequency component, a rotor current or voltage signal, at a first frequency fs*(2?s), where fs is a supply frequency of the exciter stator and s is an exciter slip, it is determined whether the exciter suffers from an inter-turn short circuit in an exciter stator winding or not. On the basis of a presence of a frequency component, in the case of a stator current signal or a stator voltage signal, at a second frequency fs*(1?2*s), it is determined whether the exciter suffers from an inter-turn short circuit in an exciter rotor winding or not. Presence of frequency components at the first and/or second frequencies in windings of an AC/AC exciter indicate the mentioned fault conditions.