Breakdown voltages in thrust bearings: Behavior and Measurement

Graf, Simon; Werner, Michel; Koch, Oliver; Götz, Stefan; Sauer, Bernd

doi:10.1080/10402004.2023.2185560

Cited by 13 publications

(8 citation statements)

References 10 publications

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“…Gerät zur erweiterten Schmierstoffanalyse-device for advanced lubricant analysis) can be operated in a four-ball apparatus. The reliability and quality of this test system have been demonstrated in a large number of publications [6,[21][22][23][24]. A schematic sketch of the test fixture is shown in Figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…In order to create comparable conditions for all tests, the actual test was preceded by a mechanical running-in phase that is identical for all test specimens. During this phase, the roughness peaks of the raceway surfaces were smoothed and a constant mechanical-electrical behavior was established [6,[21][22][23]. As operating conditions, an operating time of 16 h, an axial load of 2400 N, and a speed of 1000 rpm were used.…”

Section: Experiments Description and Boundary Conditionsmentioning

confidence: 99%

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Influence of Parasitic Electric Currents on an Exemplary Mineral-Oil-Based Lubricant and the Raceway Surfaces of Thrust Bearings

2023

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Within this paper, electro-mechanical long-term tests on a thrust bearing were presented. The effects of an additional electrical load on the bearing raceways and the used lubricant were investigated. Chemical investigations and viscosity measurements were presented, which show the changes in the lubricant. These investigations were compared with the electrical loads and the occurring raceway damage. In addition, a comparison was made with mechanical reference tests. This procedure makes it possible to classify the changes that occur due to the electrical load and to distinguish the effects from each other. The background to these investigations is the increased occurrence of parasitic currents in electric motors, which can lead to damage to machine elements. The phenomena that occur here are new challenges in the development of drive trains.

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Section: Methodsmentioning

confidence: 99%

Section: Experiments Description and Boundary Conditionsmentioning

confidence: 99%

Influence of Parasitic Electric Currents on an Exemplary Mineral-Oil-Based Lubricant and the Raceway Surfaces of Thrust Bearings

2023

Self Cite

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“…Muetze [15] investigated the influence of factors such as motor design, operational parameters, and the interconnection between the motor and inverter on bearing current, proposing potential mitigating strategies. Graf [16], focusing on thrust bearings, determined that the breakdown voltage is contingent upon variables such as oil film thickness, load, and current frequency. Gonda et al [17] conducted experimental investigations on a bench scale to elucidate the impact of grease conductivity on bearing currents.…”

Section: Introductionmentioning

confidence: 99%

Study on Grease Lubrication and Electric Erosion Characteristics in AC Electric Fields

Li,

Guo,

Jing

et al. 2024

Lubricants

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Protecting motor bearings from electric erosion is crucial as electric vehicles evolve. To better understand how lubrication interacts with electric discharge within motor bearings during varying speeds of vehicle operation, an optical ball-on-disk tribometer was modified to investigate the influence of alternating current (AC) electric fields on film thickness, friction force under various lubrication regions, and discharge characteristics. The study revealed that in AC electric fields, as the lubrication state shifts from mixed lubrication to fluid lubrication region, the electrical characteristic of the lubricating oil film changes from resistive to capacitive, accompanied by an increase in discharge frequency. Under the elastohydrodynamic lubrication (EHL) region, an electrical potential difference between the surfaces separated by the lubrication film leads to a reduction in film thickness, which can be attributed to the generation of Joule heating. If the potential difference across the oil film increases to the threshold voltage, destructive discharge occurs with the emission of a significant amount of purple light. Joule heating generated by the AC electric fields also results in a reduction in the friction coefficient under the fluid lubrication region. However, due to the reduction in film thickness, the lubrication state eventually moves to mixed lubrication, leading to a substantial increase in the friction coefficient. In addition, the study also investigated the use of grease with a nanographite conductive additive. It was found that inappropriate additive amounts can lead to discharge phenomena occurring outside the contact region.

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“…Ideally, bearings operate in an Elasto-Hydrodynamic Lubrication (EHL) regime [1][2][3], with contact surfaces fully separated by a thin layer (about 50 nm to 1 µm thick) of pressurized lubricant film, enabling efficient load transmission. Under mixed lubrication conditions, e.g., lower speed-to-load ratio or lower lubricant viscosity, direct metallic asperity contact occurs, leading to higher friction and higher risk of damage and wear [4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Experimental Analysis of Rolling Torque and Thermal Inlet Shear Heating in Tapered Roller Bearings

et al. 2023

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The investigation in this article focuses on the rolling resistance torque and thermal inlet shear factor in tapered roller bearings (TRBs) through systematic experiments using a modular test setup. TRBs typically operate under Elastohydrodynamic Lubrication (EHL) conditions. At sufficiently high speeds, the majority of rolling friction is due to a significant shift of the pressure centre in the EHL contact. While at lower speeds, sliding friction in the roller-rib contact becomes dominant, which operates under mixed lubrication conditions. Limited literature exists on the impact of inlet shear heating on effective lubricant temperature (Tin_c) and rolling friction in TRBs. To fill this gap, experimental measurements of the total frictional torque under axial loading at different speeds and oil temperatures are performed. With existing models for different friction contributions described in the literature, the rolling resistance due to EHL has been determined for various operating conditions. The effects of dimension-less speed (U), material (G), and load (W) parameters have also been investigated. Under fully flooded conditions, it was observed that the influence of material (G) and load (W) parameters on rolling friction is minor, while the impact of velocity (U) is significant. In the context of rolling resistance, the heating due to shear of the lubricant in the inlet zone plays a significant role. For higher rotational velocities, the estimated rotational torque reduction resulting from inlet shear heating was found to be approximately 6–8%.

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Breakdown voltages in thrust bearings: Behavior and Measurement

Cited by 13 publications

References 10 publications

Influence of Parasitic Electric Currents on an Exemplary Mineral-Oil-Based Lubricant and the Raceway Surfaces of Thrust Bearings

Influence of Parasitic Electric Currents on an Exemplary Mineral-Oil-Based Lubricant and the Raceway Surfaces of Thrust Bearings

Study on Grease Lubrication and Electric Erosion Characteristics in AC Electric Fields

Experimental Analysis of Rolling Torque and Thermal Inlet Shear Heating in Tapered Roller Bearings

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