Magnetic Properties of Ferromagnetic Particles under Alternating Magnetic Fields: Focus on Particle Detection Sensor Applications

Abstract

The electromagnetic wear particles detection sensor has been widely studied due to its ability to monitor the wear status of equipment in real time. To precisely estimate the change of the magnetic energy of the sensor coil caused by the wear particles, the magnetic property models of wear particles under the alternating magnetic field was established. The models consider the hysteresis effect and the eddy current effect of the wear particles. The analysis and experimental results show that with the increase of the effective field frequency, the change of the magnetic energy caused by the wear particles gradually decrease, which makes the induced electromotive force output by the sensor reduce with the decrease of the particle speed, so a signal compensation method is presented to obtain a unified signal when the same wear particle passing through the sensor in different speeds. The magnetic coupling effect between the two adjacent wear particles is analyzed. The result illustrates that the change of the magnetic energy caused by the dual wear particles system is larger than the sum of the energy variation caused by two independent wear particles, and with the increase of the interparticle distance, the magnetic coupling effect gradually weakens and disappears.

Comprehensive Improvement of the Sensitivity and Detectability of a Large-Aperture Electromagnetic Wear Particle Detector

“…Therefore, the resonant capacitors C 1 and C 3 are connected to the left and right exciting coils of the sensor in parallel, and the resonant capacitor C 2 is connected to the inductive coil in series. The general working principle of the sensor has been expounded in Reference [22]. In order to achieve the flow requirements of wear monitoring for large-scale machines, the inner diameter of the sensor is set to 7 mm.…”

“…The metal wear particles passing through the sensor lead to magnetic perturbation of the sensor. More specifically, ferromagnetic particles enhance the local magnetic flux density, while non-ferromagnetic particles decrease the local magnetic flux density [22]. In these cases, the change of the magnetic flux through the exciting coil and the inductive coil can be expressed as (1) and (2), respectively:Δϕe=true∑true∫ΔBnormalpfalse(x,yfalse)ds=Δfalse(L×Ifalse) Δϕi=Kfalse(1−sans-serifλfalse)false(ϕe1−ϕe2false) where, ϕe is the magnetic flux through the exciting coil, ΔBp is the change of magnetic flux density in the sensor caused by particles, L is the inductance of the exciting coil, I is the current through the exciting coil, K is the gain factor of magnetic flux through the inductive coil, λ is the magnetic flux leakage coefficient, which is closely related to the sensor structural parameters, and ϕei is the magnetic flux through the i th exciting coil.…”

A Novel Method for Detecting Ferromagnetic Wear Debris with High Flow Velocity

“…Voltage-type output sensors generally consist of multiple coils including excitation coils and induction coils. When ferromagnetic particles pass through, the induced electromotive force of the induction coil will change, and the sensor will output a voltage pulse [34]. This type of sensor often has high sensitivity and throughput [35].…”

A Wear Particle Sensor Using Multiple Inductive Coils Under a Toroidal Magnetic Field

“…Through inductive or eddy current methods, particle movement changes the magnetic field distribution [14][15][16][17].…”

“…Jia's also modeled wear particles, magnetic fields, and the coupling between adjacent particles. That group found that the magnetic potential generated by two passing particles was larger than that of the two separately superimposed particles, and the distance between the two particles was inversely proportional to the magnetic coupling effect, providing a reference model for electromagnetic coupling [17].…”