How to Optimise Electric Vehicle Powertrain Testing

Energy consumption and range are essential information for the driver of an electric vehicle. Less consumption means lower cost and longer range means greater convenience. Engineers in R&D also look at this information, but from a completely different angle: They aim to achieve the highest efficiency by minimizing energy losses; for individual components, at the sub-systems level, and at the level of the entire vehicle.

When Engineers examine the drivetrain, they consider more than just motor efficiency. Where do the energy losses occur? In transmission from the AC network to the battery? In the energy storage? In the conversion from DC battery back to AC again? In the inverter? Or the motor? Engineers seek to optimise the entire combination of battery inverter and motor that converts the electrical energy into mechanical power. Last but not least, they need to check that the motor controller, which regulates the communications between these three units, works correctly.

The way these components cooperate impacts efficiency more than mere power. Combining a powerful battery with an effective inverter and an efficient motor doesn’t automatically guarantee that a drive system is as efficient as it could be.

HBM’s End-to-End e-Mobility Solution

HBM’s testing solutions for electric drivetrains use the so-called “cycle detect” technology to make efficiency mapping ten times faster. By accelerating the measurement time for individual set points to the range 0,5 to 1 second, the production of multi-dimensional efficiency maps can be cut from weeks to days or even hours. Since the raw data are available at any time, the engineer can reference previous tests if anything goes wrong – without needing to re-run the test series.

Another important factor comes into play here - accuracy: To achieve reasonable measurement uncertainty for derived values such as power loss or efficiency, only the most accurate power analyzer and the most accurate sensors will be good enough. Consider an inverter with a rated power of 500 kW input and 475 kW output which equals a loss of 25 kW. If the measurement chain error is 1%, the measured values are +/- 5 kW input, +/-4.75 kW output, giving a cumulative measurement uncertainty for energy losses of +/-9.75 kW – the cumulative measurement uncertainty of 39% is far from satisfactory. If, however, the measurement chain error is 0.1%, cumulative measurement uncertainty for the power loss is 3.9%. Obviously, the more accurate the equipment, the more reliable the test results, and the more meaningful the insights on motor calibration will be.

HBM’s high-precision Power Analyzer is complemented by a range of sensors for measuring voltage, current, torque/speed with best-in-class accuracy ratings and the highest safety standards. They are certified for e-drive test systems and perfectly blend into the GENESIS HighSpeed hardware for an integral solution.

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