Test data under examination

The development of electric or hybrid drive vehicles has become increasingly important as fuel prices continue to climb and environmental awareness gathers momentum. Engineers are constantly being challenged to improve the design and efficiency of these machines especially since electric-drive vehicles are generally perceived as having a limited range caused by inadequate battery technology.

Because of this a lot of effort has been expended on improving the range and operational capacity through developing more powerful batteries while designing lighter vehicles has also been a focus for improvements. However, the focus on reducing valuable energy losses within the drive train from the battery to the final output at the road has proved elusive although it offers significant potential for improvements.

One of the challenges in gaining ground in this area is the development of improved measurement technology so that design engineers can more easily determine where improvements can be made. In many cases power analysers are often used to determine the motor input and torque transducers are used to determine motor output as a way of determining the efficiency of electric motors. The difference between the respective electrical power input into the motor and the resulting mechanical power output by the electric motor is considered the energy loss.

HBM believes that this is too crude and generic an approach to give engineers any detailed analysis about the cause of losses such as inverter control algorithms or motor functionality in certain conditions. For example, highly dynamic power measurements at more than 50 measurements per second are technically difficult while power analysers simply deliver the final results rather than the raw data that can provide important knowledge to facilitate understanding of the process driving efficiency improvements.

In addition, the various measurement devices are frequently supplied by different manufacturers and thus need to be laboriously synchronized before any test. The failure of engineers to undertake proper synchronisation can easily lead to measurement errors. However, engineers need to have reliable test and measurement equipment with adequate capability to gather relevant data so that the efficiency of these challenging machines can be improved.

To meet this demand HBM has developed its eDrive test solution as an alternative approach utilising its Genesis HighSpeed measurement data acquisition system and T12 torque transducer.

Precisely defined

These complementary measurement tools make it possible to carry out long-term tests with precisely defined characteristics and without worrying about the impact of incorrectly synchronized equipment. Jonathan Green, HBM’s Senior Sales Engineer comments, "HBM is committed to providing the most powerful measurement tools for this developing and exciting area of automotive technology.”

HBM’s eDrive test solution has been developed to provide continuous and synchronous acquisition of both electrical and mechanical power at rates of up to two million measurements per second per channel. HBM’s system continuously monitors variations in both voltage and current – both in DC at the battery pack and in AC downstream of the converter – as well as the torque and rotational speed output by the electric motor.

The Genesis HighSpeed DAQ-based eDrive approach gives test engineers access to a wide spectrum of raw data that can be analysed and used for feedback to modifications in the drive train for greater electrical efficiency. The raw data enables engineers to access and precisely evaluate aspects including true or apparent power calculations, inverter switching frequency analysis or motor parameter extraction for example.

This approach is far more comprehensive than the numbers computed by a traditional power meter since it enables detailed analysis and result verification in demanding motor/test setups. It is the raw data that provides engineers with the core knowledge they need during research to intimately understand the process and then develop greater efficiency.

HBM is constantly exploring various in-depth solutions for capturing data from the mechanical and electrical components found in a variety of hybrid drives ranging from parallel hybrids through to fuel cell vehicles. Adds Green: "It is all about the ability to capture and analyse different data in dynamic applications easily so as to calculate and improve the efficiency of hybrid drives."