Magnitude and Phase Measurements of Flux Density Profiles in AC Machine Airgaps

The development and testing of a technique capable of measuring and displaying the instantaneous flux density profile in the airgaps of ac electromagnetic machines is described. An over-layed system of flexible printed-circuit coils is used, which permits measurements to be made under rotating conditions in airgaps as small as 0.3 mm, giving good profile definition over the whole of the airgap. The signals are processed on line by a digital computer. The ability to cover large areas and small airgaps with on-line signal processing gives the technique considerable advantage over existing methods.