# A Survey on Mission-Profile-Based Stress Testing of Electric Motor Drives
## 3 Mission-Profile-Based Stress Testing Methods
### Stress Testing Methods
#### 3.2.1 Testing Electric Motors  
Practices for testing synchronous and induction machines have been refined and thoroughly documented over the years in IEEE Standard [59]. This standard provides guidelines for performing and documenting widely accepted and commonly applicable tests on multiphase induction motors and generators. These guidelines help ensure uniformity and reliability in motor testing, and even custom test procedures should follow IEEE standards to ensure consistent and comparable results. In [60], ten different duty cycles of a three-phase induction motor are discussed. Duty cycles are defined as load cycles to which the induction motor is exposed throughout its lifespan, including starting, stopping, no-load, and loading conditions. For each duty cycle, a specific sequence and duration of time are defined, and their effects on motor heating are analyzed. Additionally, the corresponding temperature profiles are presented. The authors in [61] discuss methods for evaluating the quality of the stator and rotor of electric motors, focusing on the insulation quality, rotor bars, and short-circuit rings. Corresponding tests are executed to evaluate such failures. In [62], a mission profile emulator for a permanent magnet synchronous motor (PMSM) is proposed. The emulator is based on a three-phase power electronic converter that replicates the electromagnetic properties of the PMSM. The proposed solution is evaluated through simulations and experiments conducted under speed and load profiles, and the results are compared accordingly. While the emulator effectively replicates the electrical behavior of the drive, it does not account for other forms of stress like thermal and mechanical loads, which are essential for accurately capturing the real operational response of the system. In research papers dealing with insulation testing, there are several different approaches to procedures reported. In [63], an automated test rig for the efficiency testing of a converter-fed induction motor is presented. The motor's efficiency was measured under two types of load conditions. In the first test series, the motor was loaded in steps defined by the IEC 60034-2-1 standard, ranging from 125% to 25% of the motor's rated torque. This method induces thermal stress on the stator windings, which depends on the current, and mechanical stress on the bearings. The second test series involved voltage loading in steps defined by the same standard, ranging from 110% to 30% of the motor's rated voltage. The advantage of this method lies in its automation, which enables shorter transition times between load steps, reducing the risk of excessive heating. Nevertheless, a limitation is that it does not account for temperature profiles or mechanical stress transitions between load changes, which are relevant for real-world operating conditions. A different approach to testing motor's insulation is proposed in [64]. The testing procedure includes 60 thermal cycles, each lasting an average of nine hours. The time under stress for the motor's insulation is accelerated by blocking the rotor's shaft. In this case, the mean time to failure (MTTF) was 550 h of testing. The proposed solution can be further enhanced by estimating the mechanical stress caused by the elevated temperature of the motor. The effect of the PWM switching frequency on the stator insulation has been studied in [36] by measuring phase currents and voltages at different switching frequencies. An increase in stress parameters indicates insulation aging, which, in accelerated testing, leads to degradation. This approach allows the estimation of the component's lifetime without causing complete insulation failure. The authors of [65] present a testing procedure based on a temperature mission profile for evaluating motor insulation in vehicles. The procedure involves accelerated aging tests, where insulation specimens are subjected to thermal cycles with temperature profiles ranging from 200 \({}^{\circ}\)C to 260 \({}^{\circ}\)C over varying time periods.