Analysis and determination of mechanical bearing load caused by unbalanced magnetic pull

Abstract

Purpose – The purpose of this paper is to focus on the mechanical bearing load caused by the unbalanced magnetic pull (UMP), which is studied in detail. The applied approach is based on an analysis of static and dynamic eccentricities at different positions and different amplitudes. The influence of the operating points is calculated to show the effective bearing load for machines operating at different speeds. The decreasing lifetime of the applied bearings is examined and evaluated in detail. Design/methodology/approach – To evaluate the proposed methodology a permanent magnet synchronous machine (PMSM) with buried magnets is used. To consider effects of slotting and saturation, a finite element (FE) model is employed. The Monte Carlo method is used to determine the most likely amplitudes of the eccentricities. Calculating the UMP for all possible operating points using a control strategy for the machine and coupling this results with a drive cycle, determines the effective force acting on the bearing. Findings – It has been shown that the position of the eccentricity has a not significant influence on the behavior of the UMP and may therefore be neglected. The amplitude of the eccentricity vector influences the amplitude of the UMP including all harmonic force components. For technical relevant eccentricities, the influence is approximately linear for the average and the dominant harmonics of the UMP. In most cases, it is sufficient to displace the rotor at an arbitrary position and amplitude. It is sufficient to simulate one type of eccentricity (static or dynamic) with an arbitrary value of displacement (rotor or stator) to evaluate all possible airgap unbalances. Using stochastic simulations of the eccentricity amplitudes enables an a priori design and lifetime estimation of bearings. Originality/value – This paper gives a close insight on the effect of mechanical bearing load caused by rotor eccentricities. The effect of the position of the eccentricity vector, the operational range and a drive cycle are considered. A stochastic simulation and an empirical lifetime model of one bearing gives an example of using this methodological approach.

Study on Unbalanced Magnetic Pulling Analysis and Its Control Method for Primary Helium Circulator of High-Temperature Gas-Cooled Reactor

“…In fact, the geometrical eccentricity between the stator and the rotor is derived from two parts, one part is called static eccentricity, which is caused by the misalignment in the installation, and the other part is called dynamic eccentricity, which is caused by unbalanced force, such as the rotor mass imbalance and sensor runout [6]. Due to the complexity of high-frequency vibration analysis, the high-frequency of the UMP has been ignored in the Section 2.2, and the only double-frequency components are retained.…”

“…There are many researches on multi-frequency vibration caused by the geometric center misalignment between the rotor and the stator in traditional mechanical bearings [5][6][7][8][9][10][11]. Ruf [6] focused on the mechanical bearing load caused by unbalanced magnetic pull (UMP) based on an analysis of static and dynamic eccentricities at different positions and different amplitudes. The nonlinear vibration of the rotor with UMP has been extensively investigated by Xu [7].…”

Effect of motor rotor eccentricity on aerostatic spindle vibration in machining processes

“…When the spindle rotates, the RMF F causes the spindle rotation around the mass center. As seen from Figure 8, the Z axial displacement caused by RMF can be determined as equation (10) ÁL…”

“…Therefore, many researchers have focused on motor performance. [7][8][9] Ruf et al 10 and Li et al 11 studied the RMF caused by the motor rotor eccentricity (MRE), which had a significant influence on the PM motor. The MRE causing an uneven air-gap was inevitable during the manufacturing and assembly process, which induced the unbalanced force and vibration.…”

Study on Unbalanced Magnetic Pulling Analysis and Its Control Method for Primary Helium Circulator of High-Temperature Gas-Cooled Reactor

“…There are many researches on multi-frequency vibration caused by the geometric center misalignment between the rotor and the stator in traditional mechanical bearings [5][6][7][8][9][10][11]. Ruf [6] focused on the mechanical bearing load caused by unbalanced magnetic pull (UMP) based on an analysis of static and dynamic eccentricities at different positions and different amplitudes. The nonlinear vibration of the rotor with UMP has been extensively investigated by Xu [7].…”