Design on Electromagnetic Detection Sensor on Wear Debris in Lubricating Oil

The detection technology on wear debris in lubricating oil is critical to ensure the safe operation of the engines. In this paper, a triple-coils reverse double-excitation solenoid sensor is introduced. Assuming the debris is spherical, via time-harmonic electromagnetic field analysis method, we derived the analytical expression on the impedance increment of the induction coil when the debris flows into the coils. The impedance increment depends on the radius and movement speed of the debris, and the dimensions of the coils. Theoretical results are verified by the Ansoft simulations and physical experiments. Based on the impedance expression, several methods are presented to improve the sensitivity of the sensor.