I recently ran a few experiments to simulate the effects of shaft voltages on motor bearings through using a simplified experimental rig. The rig simulates bearing contact. I applied a DC source across the rig using carbon slip rings and connected a resistor in series to limit the maximum current.
The data from the experiment is quite interesting.
A schematic of the simplified circuit is shows as:
The voltage supply was set to 10 V.
The elastohydroydnamic film is said to behave as a capacitor, assuming the discs are completely serrated by a lubricating film.
The data recorded:
and
The first graph (blue) recorded RV (resistor potential difference) and the second graph (red) recorded the voltage across the bearing contact.
What's very strange to me is the fluctuation in voltage above and below 0. An analytical solution would suggest that the voltage across the rig should not be negative, due to captive or ohmic behaviour.
Any possible reasons for the negative potential difference?
