Abstract： Magnetic powder detection is an important method to detect the welding seam and its raw materials of ferromagnetic pressure equipment as well as the surface and near surface defects of machined parts. To investigate the difference of magnetic powder detection depth when three types of alternating currents (including sine wave, square wave, and triangular wave) were used at different frequencies, the experimental detection system of artificial slot and variable frequency alternating current magnetic yoke with different buried depths was designed and manufactured. The difference of detection depth of three kinds of variable frequency alternating current electromagnetic powder was explored under the same fluorescent magnetic powder detection conditions. The results showed that compared to the sine wave and triangular wave, the square wave had a deeper detection depth and higher detection sensitivity during the detection of nonopen defects near surface with certain burial depth. Therefore, the square wave alternating current could be used as a useful complement to exciting current for magnetic powder detection.
