43 Motor testing | Insight E-Mobility Engineering | March/April 2025 vehicle’s systems, including its drive motors, while corrosion testing assesses the effects of environmental factors such as moisture and road salt. Electrical machines such as motors, generators and power electronics, including inverters and DC-DC converters, are all sources of radiofrequency emissions, so further specialised testing is carried out to ensure the levels of electromagnetic interference (EMI) are low enough to comply with the standards for electromagnetic compatibility (EMC). Increasingly, both virtual and hardware-in-the-loop (HIL) simulation are used to replicate real-world conditions, stressing motor and control systems before full physical systems are put together. EME spoke with several companies that address motor testing to gauge their different approaches, from comprehensive coverage to highly specialised products and services. Tailored solutions Autforce, for example, offers test benches and software, and it provides motor testing with a focus on customisation and measurement precision, combining automation, external measurement integration and simulation tools. The company’s tailored solutions accommodate a wide range of electrical machine sizes and power ratings. Past projects include test-bench systems for motors producing just 7.5 kW with a maximum speed of 15,000 rpm, ranging up to motors rated at 650 kW with 11,000 Nm of torque, 800 A peak current and speeds reaching 17,000 rpm, according to test-bench engineer Rainer Jung. Motor types supported include permanent magnet synchronous motors (PMSM), induction motors (IM) and switched reluctance motors (SRM). also carried out at the powertrain level to assess responses to the temperature and humidity ranges in which the motor is intended to operate, as well as probing the performance of the thermal management system, particularly cooling of the motor and inverter. Further, efficiency analysis involves measuring electrical input and mechanical output to gauge how much energy is lost in the conversion, and the impact of harmonics on motor performance and energy use is also examined. It is particularly important to look closely at harmonics in motors controlled using non-sinusoidal waveforms, such as those produced by variable-frequency drives (VFDs) or other switching power supplies, as these can cause harmonic distortion. In turn, that can lead to additional heating in the motor windings and power supply, mechanical vibration and electromagnetic interference. Harmonic distortion can cause irregularities in the motor’s torque output, leading to undesirable fluctuations, known as torque ripple. It can also contribute to additional losses, which is a particular problem in systems designed for high-efficiency, where even small inefficiencies can be significant. At vehicle level, the motors are stressed along with the rest of the vehicle on chassis dynamometers that test performance under simulated road conditions, while acceleration and braking tests measure responsiveness in various scenarios. More specific tests are carried out on high-voltage test benches to validate the interaction between the battery, inverter and motor, while regenerative braking analysis examines how well these components operate together in energy recovery mode. Environmental and durability assessment includes vibration and shock testing to simulate real-world stresses that could affect all the It is particularly important to look closely at the harmonics in motors controlled using non-sinusoidal waveforms Laboratory bench for testing electric motors in the prototype phase and for small series production offering configurable sequence changes in terms of tests and speeds up to 3000 rpm, plus data analysis (Image courtesy of Autforce)
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