System and method for inspection of a generator stator core step iron region with the rotor in-situ

An inspection crawler apparatus for inspecting a step iron region of a generator stator core bore, while the rotor remains in situ therein, the step iron region oriented proximate an axial end of the generator stator core, and the generator defining a rotor gap between the stator core bore and its opposed rotor along an axial dimension of the stator core bore, comprising:

• a translatable inspection carriage, having a bottom surface;
• an extension arm having a proximal end pivotally coupled to the inspection carriage by an extension arm pivot mount along a first pivot axis;
• a Chattock coil assembly, having:
• a coil housing retaining a Chattock coil,
• an elongated sensing surface defined by the coil housing, and
• a coil housing pivot mount that is pivotally coupled to a distal end of the extension arm along a second pivot axis that is parallel to the elongated sensing surface;
• so that when the inspection carriage is inserted within a generator rotor gap between a generator core bore, including a step iron region thereof, and an opposed rotor, the carriage bottom surface is in opposed orientation with the generator core, the second pivot axis is oriented tangentially to radii defined by the stator core circumferential surface, including radii defined by the core's step iron region, and the Chattock coil sensing surface remains parallel with and in abutting contact with the stator core circumferential surface defined by the core's step iron region, as the Chattock coil assembly is translated along the stator core's axial dimension by the inspection carriage.

An eddy current inspection system for inspecting lamina insulation within a step iron region of a generator stator core bore, while the rotor remains in situ therein, the step iron region oriented proximate an axial end of the generator stator core, and the generator defining a rotor gap between the stator core bore and its opposed rotor along an axial dimension of the stator core bore, comprising:

• an inspection crawler, for insertion within a generator rotor gap between a generator core bore, including a step iron region thereof, and an opposed rotor, including:
• a translatable inspection carriage, having a bottom surface;
• an extension arm having a proximal end pivotally coupled to the inspection carriage by an extension arm pivot mount along a first pivot axis;
• a Chattock coil assembly, having:
• a coil housing retaining a Chattock coil,
• an elongated sensing surface defined by the coil housing, and
• a coil housing pivot mount that is pivotally coupled to a distal end of the extension arm along a second pivot axis that is parallel to the elongated sensing surface;
• an eddy current excitation generator, for coupling to a generator stator core bore and generating an excitation current therein;
• and
• an eddy current inspection analyzer system, coupled to the Chattock coil, for correlating changes in coil output signal with variations in lamina insulation properties;
• so that when the eddy current excitation generator is coupled to and generating excitation current within a generator core bore and the inspection carriage is inserted within a generator rotor gap between that generator core bore, including a step iron region thereof, and its opposed rotor:
• the carriage bottom surface is in opposed orientation with the generator core;
• the second pivot axis is oriented tangentially to radii defined by the stator core circumferential surface, including radii defined by the core's step iron region, so that the Chattock coil sensing surface remains parallel with and in abutting contact with the stator core circumferential surface defined by the core's step iron region, as the Chattock coil assembly is translated along the step iron region's axial dimension by the inspection carriage;
• and
• the eddy current inspection analyzer system monitors changes in the Chattock coil output that are in turn correlated with variations in lamina insulation properties within the step region.

A method for inspecting lamina insulation within a step iron region of a generator stator core bore, while the rotor remains in situ therein, the step iron region oriented proximate an axial end of the generator core, and the generator defining a rotor gap between the stator core bore and its opposed rotor along an axial dimension of the stator core bore, comprising:

• providing a generator having an in situ rotor circumscribed by a stator core bore, and a step iron region oriented proximate an axial end of the generator stator core, the generator defining a rotor gap between the stator core bore and its opposed rotor along an axial dimension of the stator core bore;
• providing an eddy current inspection system, including:
• inspection crawler, having:
• a translatable inspection carriage, having a bottom surface;
• an extension arm having a proximal end pivotally coupled to the inspection carriage by an extension arm pivot mount along a first pivot axis;
• a Chattock coil assembly, having:
• a coil housing retaining a Chattock coil,
• an elongated sensing surface defined by the coil housing, and
• a coil housing pivot mount that is pivotally coupled to a distal end of the extension arm along a second pivot axis that is parallel to the elongated sensing surface;
• an eddy current excitation generator, for coupling to a generator stator core bore and generating an excitation current therein;
• and
• an eddy current inspection analyzer system, coupled to the Chattock coil, for correlating changes in coil output signal with variations in lamina insulation properties;
• inserting the inspection carriage within the generator rotor gap so that the carriage bottom surface is in opposed orientation with the generator core circumferential surface;
• translating the carriage along the stator core axial dimension, so that the Chattock coil sensing surface is parallel with and in opposed abutting contact with the stator core circumferential surface defined by the core's step iron region;
• coupling the eddy current excitation generator to a generator stator core bore, and generating an excitation current therein, before or after the inspection carriage insertion;
• coupling the eddy current inspection analyzer system to the Chattock coil, before or after inspection carriage insertion;
• for receiving an output signal therefrom and correlating the output signal with lamina insulation properties;
• and
• translating the Chattock coil sensing surface along the step iron region by translating the carriage along the stator core and monitoring changes in the Chattock coil output signal with the eddy current inspection analyzer system.