Material Properties Effects of Hollow Shafts on the Performance of Rotational Eddy Current Speed Sensor

The evaluation of the material properties of hollow shafts and their effect on the performance of rotational eddy current speed sensors is presented in this paper. The eddy current sensor has two saddle excitation and pickup coils located perpendicularly. The conductivity and relative magnetic permeability of rotating shafts affect the sensor sensitivity. A 3D analytical method is used to analyze the sensor performance and for parametric calculations. The skin effect and 3D distribution of induced eddy current in the rotating hollow shaft are considered in the 3D analytical method. A measurement for the eddy current sensor is conducted at various speeds. A hollow iron shaft and a hollow aluminum shaft are considered in the modeling and the measurement to evaluate the material effects on the sensor performance. Finally, the effects of the sensor coils dimensions and the gap between coils and the rotating shaft are analyzed to further evaluate the vulnerability of the sensor against shaft material properties.