System for the insulation fault detection of AC electric machines cores, based on magnetic field scanning

A new method of detecting insulation faults in cores of AC machines involves the measurement of the magnetic field near the core surface. The measurement head comprises several integrated Hall sensors. Some of the disadvantages of other methods can be thus eliminated. The method does not require a high source current and long operation time, as it is in thermal method and it offers a better resolution than the ELCID method. A dedicated computer program is used for measurement and for visualization of results which could be similar to those obtaining from the thermal camera. The method is well applicable when handling synchronous generators and induction machines. The paper summarizes the field calculation data obtained by the FEM simulations.