Electromagnetic stator insulation flaw detector
AssigneeSiemens Westinghouse Power Corporation
InventorsMark William Fischer, James William Shelton, Michael J. Metala
Life of this patent
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Abstract
An electromagnetic generator inspection system that employs a plurality of excitation frequencies and comprises one or more pickup coils that monitor a portion of the interior of a stator core to provide an output that identifies the location, severity and radial depth of any flaw in the insulation covering the laminations that are monitored.
Claims28
An electrical generator inspection system for detecting insulation breakdown axially between two or more adjacent laminates of a generator stator core comprising:
- an electromagnetic detector having an excitation coil for carrying an alternating current and inducing eddy currents in the laminates, said electromagnetic detector providing output signals representative of fault currents detected due to defects in the insulation between laminates axially along the stator core, said output signals providing information on the axial location along the stator core at which the fault currents are detected;
- and
- means for varying a frequency of the alternating current so that said output signals also provide information on a depth, radially, of the fault currents within the laminations.
A method of inspecting an electrical generator stator core to determine insulation breakdown axially between two or more adjacent laminates of a generator stator core with an electromagnetic detector having an excitation coil for carrying an alternating current and means for varying the frequency of an ac current connected to the excitation coil, comprising the step of:
- positioning the excitation coil so that it will create a magnetic field that will generate eddy currents in the area of the stator to be inspected;
- setting the ac current at a first frequency;
- monitoring a first output of a pickup coil positioned adjacent a first location on the stator core with the ac current set at said first frequency;
- adjusting the ac current to a second frequency which is different from the first frequency;
- and
- monitoring a second output of the pickup coil positioned adjacent the first location on the stator core with the ac current set at the second frequency.
Dependencies are inferred from the claim text.