The Analysis of Generator Excitation Current Harmonics on Stator and Rotor Winding Fault

The generator excitation current harmonics characteristic is analyzed when stator winding or rotor winding inter-turn short circuit fault has happened respectively. Armature reaction magnetic field synchronously rotates with rotor when generator operates normally, and rotor winding won´t induce additional harmonic current. But it non-synchronously rotates with rotor when the fault has happened, so additional harmonic current is induced in rotor winding. Next, through analyzing electromagnetism characteristic on stator and rotor winding fault respectively, excitation current harmonics characteristics can be obtained, it is known that the additional excitation current harmonic on stator winding fault mainly is twice electrical frequency, and that on rotor winding fault is the function of air-gap excitation magnetic field harmonic frequency, poles´ pairs of generator and rotor mechanical revolution. Finally, the excitation current of a type MJF-30-6 generator is measured in the laboratory to verify the theoretical analysis presented above