Device for surface testing profiled steel sections using the stray flux method

摘要

In the device, which employs the stray flux method, at least three electromagnets are distributed in the measurement plane around the profiled steel section to be tested. Each electromagnet is connected to its own alternating voltage source which exhibits a phase difference with respect to the alternating voltages of the other alternating voltage sources. The distribution of the electromagnets around the profiled steel section to be tested and the phase difference of the individual alternating voltage sources are chosen in such a way that the induced magnetic field at any point on the surface has at least intermittently a sufficiently large tangential component and in particular an almost constant rms value.