Background
As the electric and hybrid-electric vehicle markets continue to grow for both on and off-highway applications, a significant amount of work has been done to develop electric vehicle drivetrain lubricant test methods. It is not well-understood how oxidation performance, a very important lubricant property, may be affected by the presence of an applied voltage or magnetic field in an electrified environment. The aluminum beaker oxidation test (ABOT), a well-known industry method, was chosen to investigate this. Additionally, this project was undertaken to help establish a new oxidation performance test method specifically for electric or hybrid-electric vehicle applications.
Approach
An ABOT rig was modified by adding a submerged coil of copper magnet wire to each test beaker. The coil serves as the voltage source to which the test fluids are directly exposed. A test matrix of varying electric conditions was conducted. Electrification conditions included varied alternating current (AC) voltages and frequencies, direct current (DC) voltage, as well as the creation of a magnetic field via an energized solenoid. The test matrix was performed on four different drivetrain lubricants – two typical automatic transmission fluid (ATF) formulations, a tractor hydraulic fluid (THF), and a gear oil used in differential applications. Dielectric constant, dissipation factor, electrical conductivity, and dielectric breakdown of the new and oxidized test fluids were also measured to assess oxidation effects on these properties.
Accomplishments
Electrification of the ABOT, as outlined in the approach, showed to have low impact on oxidation performance of the four different drivetrain lubricants overall. Introduction of the energized solenoids resulted in more severe oxidation in some cases and the DC field tests impacted the anti-corrosion performance for two of the fluids (ATF and THF). Changes in dielectric properties of the oxidized fluids were grouped by fluid type. Electrical conductivity, dissipation factor, and relative permittivity increased for both ATFs and decreased for the THF and the gear oil.