# The Influence of Load and Speed on the Initial Breakdown of Rolling Bearings Exposed to Electrical Currents

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Experimental Design

#### 2.2. Mechanical Test Setup

#### 2.3. Electrical Test Setup and Evaluation

^{®}4444 oscilloscope by Pico Technology Ltd., Cambridgeshire, UK. The bearing current is calculated as

#### 2.4. Design of Experiments

## 3. Results and Discussion

#### 3.1. Exemplary Measurement Results at a Single Test Point

#### 3.2. Influence of the Operating Point

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

AC | alternating current |

bd | breakdown |

ccd | central composite design |

DC | direct current |

DoE | design of experiments |

ir | inner ring |

or | outer ring |

rms | root mean square |

## Appendix A

**Table A1.**Tabular overview of the experiments carried out. The V-number is analog to the order in which the experiments were conducted.

Number | ${\mathit{F}}_{\mathbf{r}}$ in N | ${\mathit{F}}_{\mathbf{a}}$ in N | $\mathit{C}/\mathit{P}$ | ${\mathit{A}}_{\mathbf{Hz}}$ in mm^{2} | n in min${}^{-1}$ | ${\widehat{\mathit{V}}}_{\mathbf{longtime}}$ in V | DoE | ${\widehat{\mathit{V}}}_{\mathbf{crit},1}$ in V | ${\widehat{\mathit{V}}}_{\mathbf{crit},2}$ in V |
---|---|---|---|---|---|---|---|---|---|

V015 | 1800 | 900 | 20.0 | 5.68 | 7000 | 4 | cubic | 5 | 3 |

V014 | 1800 | 900 | 20.0 | 5.68 | 7000 | 16 | cubic | 6 | 3.5 |

V032 | 1800 | 900 | 20.0 | 5.68 | 2000 | 4 | cubic | 3 | 2.5 |

V035 | 1800 | 900 | 20.0 | 5.68 | 2000 | 16 | cubic | 4.5 | 3 |

V046 | 1800 | 300 | 9.4 | 5.03 | 7000 | 4 | cubic | 2.5 | 2 |

V047 | 1800 | 300 | 9.4 | 5.03 | 7000 | 16 | cubic | 3 | 2 |

V025 | 1800 | 300 | 9.4 | 5.03 | 2000 | 4 | cubic | 3 | 2.5 |

V016 | 1800 | 300 | 9.4 | 5.03 | 2000 | 16 | cubic | 3.5 | 2 |

V053 | 600 | 900 | 9.1 | 5.70 | 7000 | 4 | cubic | 2 | 2 |

V051 | 600 | 900 | 9.1 | 5.70 | 7000 | 16 | cubic | 2.5 | 2 |

V056 | 600 | 900 | 9.1 | 5.70 | 2000 | 4 | cubic | 1.5 | 1.5 |

V020 | 600 | 900 | 9.1 | 5.70 | 2000 | 16 | cubic | 2 | 2 |

V052 | 600 | 300 | 6.7 | 5.03 | 7000 | 4 | cubic | 4.5 | 2 |

V030 | 600 | 300 | 6.7 | 5.03 | 7000 | 16 | cubic | 2.5 | 2 |

V054 | 600 | 300 | 6.7 | 5.03 | 2000 | 4 | cubic | 4.5 | 2 |

V055 | 600 | 300 | 6.7 | 5.03 | 2000 | 16 | cubic | 1.5 | 1.5 |

V024 | 2040 | 600 | 7.8 | 5.32 | 4500 | 4 | star | 7 | 3 |

V045 | 2040 | 600 | 7.8 | 5.32 | 4500 | 16 | star | 4.5 | 2 |

V049 | 360 | 600 | 13.8 | 5.34 | 4500 | 4 | star | 3 | 2 |

V050 | 360 | 600 | 13.8 | 5.34 | 4500 | 16 | star | 2.5 | 2 |

V013 | 1200 | 1020 | 7.0 | 5.84 | 4500 | 4 | star | 2.5 | 2.5 |

V012 | 1200 | 1020 | 7.0 | 5.84 | 4500 | 16 | star | 6 | 2.5 |

V017 | 1200 | 180 | 14.1 | 4.95 | 4500 | 4 | star | 5.5 | 2.5 |

V037 | 1200 | 180 | 14.1 | 4.95 | 4500 | 16 | star | 4 | 2.5 |

V022 | 1200 | 600 | 10.0 | 5.33 | 8000 | 4 | star | 6.5 | 6.5 |

V042 | 1200 | 600 | 10.0 | 5.33 | 8000 | 16 | star | 4.5 | 2.5 |

V041 | 1200 | 600 | 10.0 | 5.33 | 1000 | 4 | star | 5 | 2 |

V036 | 1200 | 600 | 10.0 | 5.33 | 1000 | 16 | star | 2.5 | 2 |

V044 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 7.5 | 2.5 |

V034 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 3.5 | 2 |

V039 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 7.5 | 2 |

V031 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 5.5 | 5.5 |

V018 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 4 | 4 |

V029 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 4 | 2.5 |

V033 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 6 | 6 |

V038 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 5.5 | 4 |

V043 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 7 | 3.5 |

V011 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 3 | 2.5 |

V023 | 1200 | 600 | 10.0 | 5.33 | 4500 | 4 | central | 0.5 | 0.5 |

V048 | 1200 | 600 | 10.0 | 5.33 | 4500 | 16 | central | 7 | 2 |

V027 | 4000 | 600 | 4.2 | 5.28 | 4500 | 4 | extra | 3.5 | 3 |

V040 | 4000 | 600 | 4.2 | 5.28 | 4500 | 16 | extra | 3 | 2 |

V028 | 1200 | 2000 | 4.2 | 6.99 | 4500 | 4 | extra | 6 | 6 |

V026 | 1200 | 2000 | 4.2 | 6.99 | 4500 | 16 | extra | 3 | 2.5 |

## Appendix B

**Figure A1.**RMS values of bearing voltage and current for the first stair (

**left**) and for the second stair test (

**right**) for six different, newly run-in bearings (V029 (

**a**,

**b**), V038 (

**c**,

**d**), V039 (

**e**,

**f**), V044 (

**g**,

**h**),V0484 (

**i**,

**j**) at ${F}_{\mathrm{r}}=1200\mathrm{N}$, ${F}_{\mathrm{a}}=600\mathrm{N}$ and $n=4500{\mathrm{min}}^{-1}$.

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**Figure 1.**Schematic representation of the experimental procedure to investigate the initial electrical breakdown.

**Figure 3.**Electrical setup: (

**a**) Signal normalized to ${\widehat{V}}_{\mathrm{G}}=1\phantom{\rule{3.33333pt}{0ex}}\mathrm{V}$ for realistic voltage application. (

**b**) circuit diagram with signal generator, voltage amplifier, current limiting resistor and test bearing, inner (ir) and outer ring (or).

**Figure 5.**rms values of bearing voltage and bearing current (

**a**) for the first stair and (

**b**) for the second stair test at ${F}_{\mathrm{r}}=1200\mathrm{N}$, ${F}_{\mathrm{a}}=600\mathrm{N}$ and $n=4500{\mathrm{min}}^{-1}$. The gaps in the measurement data are due to the saving time.

**Figure 6.**Scatter plots of the last three steps ${\widehat{V}}_{\mathrm{G}}=2\mathrm{V}$ (

**a**), $2.5\mathrm{V}$ (

**b**) and $3\mathrm{V}$ (

**c**) of the second stair test of V011. Each red dot represents a positive breakdown, each blue one a negative. Histograms display the distribution over each axis. The total number of breakdowns ${n}_{\mathrm{bd}}$ is given in each caption.

**Figure 7.**Electrical rolling bearing damage after test run: fluting on the inner ring (

**a**), discoloration of the lubricant on the rolling element (

**b**) and gray frosting on the outer ring (

**c**) [26].

**Figure 8.**Correlation matrices for input parameters radial load ${F}_{\mathrm{r}}$, axial load ${F}_{\mathrm{a}}$ and rotational speed n. Output as well as output parameters critical voltage amplitude for the initial ${\widehat{V}}_{\mathrm{crit},1}$ and the secondary damage ${\widehat{V}}_{\mathrm{crit},2}$ (

**a**) and the number of breakdowns per second ${n}_{\mathrm{bd}}/\mathrm{s}$, the apparent bearing current density $\widehat{J}$ and the apparent bearing power $\widehat{S}$ (

**b**) for the secondary damage period with ${\widehat{V}}_{\mathrm{G}}>{\widehat{V}}_{\mathrm{crit},2}$.

Level | Radial Load in $\mathbf{N}$ | Axial Load in $\mathbf{N}$ | Speed in ${\mathbf{min}}^{-1}$ |
---|---|---|---|

$-\alpha $ | 360 | 180 | 1000 |

$-1$ | 600 | 300 | 2000 |

0 | 1200 | 600 | 4500 |

1 | 1800 | 900 | 7000 |

$\alpha $ | 2040 | 1020 | 8000 |

${\alpha}^{+}$ | 4000 | 2000 | - |

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## Share and Cite

**MDPI and ACS Style**

Puchtler, S.; Maier, R.; Kuhn, M.; Burkhardt, Y.
The Influence of Load and Speed on the Initial Breakdown of Rolling Bearings Exposed to Electrical Currents. *Lubricants* **2024**, *12*, 1.
https://doi.org/10.3390/lubricants12010001

**AMA Style**

Puchtler S, Maier R, Kuhn M, Burkhardt Y.
The Influence of Load and Speed on the Initial Breakdown of Rolling Bearings Exposed to Electrical Currents. *Lubricants*. 2024; 12(1):1.
https://doi.org/10.3390/lubricants12010001

**Chicago/Turabian Style**

Puchtler, Steffen, Robert Maier, Martin Kuhn, and Yves Burkhardt.
2024. "The Influence of Load and Speed on the Initial Breakdown of Rolling Bearings Exposed to Electrical Currents" *Lubricants* 12, no. 1: 1.
https://doi.org/10.3390/lubricants12010001