The field windings in the rotor of a generator are generally an annular array of conductive coil bars arranged in slots around the outer periphery of the rotor. A connected pair of coil bars and end turns form a coil winding turn. The coil bars extend longitudinally along the length of the rotor and are connected by end turns at each end of the rotor. Several coil winding turns make up a pole. A rotor may have multiple poles.
shorted turns: The insulation separating the conductor bars or end turns of an above described type rotor may break down and cause a short circuit across one or more coils of the winding. They are called shorted turns.It can cause overheating conditions and related vibration problems.

Methodology
A flux probe sensor is introduced in the air-gap which generates a signal proportional to the rate of change of the electromagnetic flux in the air-gap.The signal from flux probe during on-line operation is monitored, the signal is integrated to generate a flux density data trace that repeats during each rotor revolution; one cycle of the flux density signal is segmented and upon detecting a variation in the repeating flux density trace, capturing the flux probe signal data during a rotor revolution period; the steps of monitoring, integrating and capturing flux data as the on-line operation progresses through various machine load, are repeated.

Reduction and analysis of the flux probe data is triggered based on the locations of the flux density zero-crossings. Automating data collection reduces generator offline periods. To reduce the amount of data stored, the processor may be programmed to capture, the flux probe data when the zero-crossing point of the flux density trace shifts from one region to another.Data sufficient to identify a shorted turn is collected by capturing flux data each time the zero-crossing timing changes. the processor is programmed to compare the amplitudes of the coils of the different poles of the flux probe signal in the time regions aligned with the flux density zero crossing. The current captured flux data is flagged by the processor as indicating a possible shorted coil turn in a given pole.

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