Magnetic flux and loss measurements using thin film sensors

Traditionally the magnetic field distribution throughout an electrical machine core is obtained by positioning miniature enamelled copper wire search coils on test laminations stacked in an experimental core. However their physical presence, when inserted in a core, changes the flux and field distribution, creates localised stress and also an air gap between two adjacent laminations. To overcome this drawback, sensors comprising a thin film structure have been deposited on the surface of several laminations by vacuum evaporation of metals. Differences between the results obtained using conventional and thin film search coils are within the limits of experimental errors.