# A Survey on Mission-Profile-Based Stress Testing of Electric Motor Drives
## 3 Mission-Profile-Based Stress Testing Methods
### Stress Testing Methods
#### 3.2.2 Testing Power Converters  
With the increasing use of power electronic devices in EMDs, the need to evaluate their reliability and lifespan has arisen due to their significant impact on system performance. Some related review papers on the testing of power electronic converters are listed in [72; 73; 74]. Consequently, a significant amount of effort has been dedicated to mission-profile-based stress testing of power electronics in EMDs. Today, the most commonly used topology of power converters in EMDs is the three-phase two-level VSI, valued for its high power output density. Most existing test methods focus on stress testing this type of inverter, as well as semiconductor devices such as IGBTs and MOSFETs. In Figure 6, a commonly used setup for testing the two-level VSI under environmental conditions is presented. These conditions can be adjusted to reflect real operating environments in practical applications. The VSI is placed inside a test chamber where the aging of the IGBT modules is monitored. Environmental conditions within the chamber such as temperature, humidity, mechanical stress, pressure, and dust are controlled by a dedicated controller to reproduce a defined mission profile. In [75], a testing procedure for a VSI is performed, utilizing combinations of different stress factors. The stress factors used are temperature, humidity, power cycling, and interruptions of power supply. The test method includes four series of loading the VSI until failure. The advantage of this testing solution is that it uses longer durations of voltage sags and simultaneously employs multiple stress factors to test the converter. However, a significant drawback is that this approach requires long testing periods until failure, and components are tested until failure, without utilizing lifetime estimations based on load profiles. In contrast, Ref. [76] analyzes the reliability of a VSI using both single stress and multiple simultaneous stress testing methods, including varying DC link voltage as an additional stress factor. While this method also involves testing until failure, it offers a more comprehensive approach to understanding VSI reliability by incorporating additional stress factors, though it still suffers from the same limitation of requiring long testing durations. The authors of [77] present a lifetime prediction model for inverter IGBT modules in electric vehicles. The FTP-75 driving cycle was used as the speed mission profile to evaluate the lifetime of the power inverter. To estimate the lifetime under test conditions from junction temperature cycling, the authors employed the Rainflow Counting Algorithm. Similarly, the FTP-72 driving cycle is used in [78]. The authors proposed a method for detecting all relevant temperature cycles within the computed temperature curve. Another test procedure for IGBT modules in traction inverter applications is provided in [79]. The input mission profile includes real-time DC voltage data, as well as the speed and torque profiles of the induction motor. The proposed solution is tested only in a co-simulation environment using MATLAB/Simulink and PLECS to obtain the junction  
Figure 6: Test chamber setup for three-phase two-level VSI. temperature profile. In [80], a power cycling procedure for semiconductor devices based on the Worldwide Harmonized Light Vehicle Test Cycle (WLTP) is proposed. A thermal profile is obtained based on the thermal simulation drive model developed in PLECS. This testing procedure can be used to SiC MOSFET or other power modules but lacks paying attention to the duration of thermal cycle. The researchers in [81] investigate the impact of solar irradiance and temperature mission profiles on photovoltaic (PV) inverters. They also consider the influence of parasitic filter elements. Paper [82] employs Monte Carlo simulation with incremental damage to estimate the reliability of a VSI under a thermal stress profile. The suggested approach is applicable to power converters designed for fault-tolerant operation.