System for core fault detection of AC electric machines, based on magnetic field scanning

A new method of detecting insulation faults in cores of AC machines is outlined. The method involves the measurements of the magnetic field near the surface of the core, using a number of parallel electronic field meters. It is demonstrated that the new method does not share the disadvantages of other methods as it does not require a high current source and long operation time compared with the thermal method. Besides, it offers a better resolution than the ELCID method. A dedicated computer program is used to measure and visualize results, which can be displayed in the form similar to those obtained from a thermal camera. The method is applicable both to synchronous generators and induction machines.