Model 3 PCS1 reliability
The work
Rameez led validation and reliability testing for the Model 3 on-board charger and DC-DC hardware, the work that decides whether a product is ready to launch at volume. He designed and implemented automated durability and stress test setups that made failures surface early and made their root causes traceable.
Findings and corrective action plans went to Tesla executive leadership, and the design updates that followed lifted fleet-wide quality metrics from 70% to over 97%. He also ran DFMEAs with design and quality teams, catching field failure risks while the design could still absorb the change.
Tesla vehicle on-board charger location
48A PCS1
Image: sourced from public teardown websites
Test setup for testing AC and DCDC conversions
Reliability chamber single-line diagram for testing multiple DUTs at the same time to increase test confidence
The junction temperature of a semiconductor device (like a diode, or the body diode of a power MOSFET) changes far too rapidly (in microseconds) to be measured with physical probes or thermocouples. Instead, the electrical properties of the semiconductor junction itself are used to measure the temperature.
The calibration step (the graph itself): Before running a transient thermal test, the device is placed in a temperature-controlled oven. A very small, constant sensing current (precisely 10 mA in this graph) is applied to avoid self-heating. The forward voltage Vf is plotted at various steady-state temperatures, yielding a highly linear relationship known as the K-factor.
The power pulse (heating): During the actual transient impedance test, a massive power pulse is driven through the device to rapidly heat the junction.
The measurement (cooling phase): The moment the heating power is abruptly cut off, the test equipment instantly switches back to the tiny 10 mA sensing current and records the rapid rise of Vf over time as the junction cools down.
Data conversion: Using the linear slope from the graph, the test software translates the raw time-resolved voltage measurements directly into an exact junction temperature cooling curve. This curve is then divided by the applied power to calculate the final transient thermal impedance profile.