47 Motor testing | Insight gauge the performance of inverterdriven electrical machines. For example, Hottinger Bruel & Kjaer (HBK) produces the eDrive series, offered as a comprehensive power analysis and data acquisition system that is designed to support testing across various motor types and applications. Based on digital cycle detection, these systems are designed to connect to a PC that can display power readings in real-time, store results and raw data, and analyse stored data in post-processing. The company says eDrive analysers deliver reliable results, even through dynamic load changes; conditions that reveal weaknesses in more conventional power meters. The eDrive family accommodates a wide range of motor sizes and power ratings, and it is compatible with the broad range of sensors needed to gather data from motors ranging from small household appliances and pumps (measured in watts) to larger industrial motors, EV powertrains and elevators (in kW), and even large-scale applications such as trains, ships and wind energy systems (in MW). Furthermore, the system is compatible with various motor types, including PMSM, induction motors, switched reluctance motors, machines with large numbers of phases (six, 12 or even up to 21) and linear motors. Automation is available on the data storage and analysis side, including automated file transfer, file conversion and batch processing of multiple tests. Additionally, the system supports all levels of the development ‘V’ model, from basic research and component development to subsystem and full-system integration testing, the company says. Cycle detection is a digital process used to identify and track the fundamental frequency of an electrical signal in real-time, enabling the analyser to make accurate power calculations on a per-cycle basis. By detecting individual cycles, the eDrive system ensures power, torque and efficiency measurements are computed with the correct averaging intervals. This level of granularity is essential in applications where dynamic performance evaluation is required. Digital real-time cycle detection uses a built-in crosscheck function to detect any failed cycles, preventing inaccurate power calculations from being recorded. This ensures accuracy, even when the motor’s rotational speed fluctuates rapidly, typically under transient load conditions or in standardised driving cycles, such as the Worldwide Harmonised Light Vehicles Test Procedure (WLTP). This is particularly beneficial in scenarios with variable-speed drives, where traditional analysers that rely on analogue phase-locked loop (PLL) techniques may struggle to maintain accurate frequency tracking. The eDrive systems minimise measurement inaccuracies by dynamically adjusting the input range of loads. A real-time measurement uncertainty calculation, which HBK calls unique, provides users with uncertainty values for every setpoint, even under varying loads. Harmonic analysis capabilities include grid harmonics (meeting the IEC 610004-7 standard) at the inverter input and wideband harmonics at the inverter output. These measurements are performed with 18-bit resolution, ensuring high precision and the ability to detect low amplitude harmonics. The system provides detailed harmonic insights that are critical for evaluating power quality and motor performance. E-Mobility Engineering | March/April 2025 E-motor test stand coupled with a climate chamber, the stand equipped with an integrated IMC data acquisition system to the left of the unit under test (Image courtesy of IMC) Highly sampled, and synchronised measurement data is essential for the complete acquisition and evaluation of a DUT
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