To keep energy consumption down in industry, in traffic and in the home, we are seeing increasing demands to make electric drives more energy efficient. Determining the extent to which electrical machines and power converters can be made more efficient involves high-precision measuring devices, measurement techniques and analysis processes.
The Steinbeis Transfer Center Energy-efficient power electronics for electrical drives and power storage systems at Aschaffenburg University of Applied Sciences joined forces with Hottinger Baldwin Messtechnik in Darmstadt to draw up specifications for these measuring devices and the associated data analysis. Responding to high customer requirements, the project partners aimed to simultaneously record and process electrical and mechanical readings in real time.
To measure energy efficiency in relation to specific applications and obtain meaningful data, the project partners used a measurement approach employing load points that change over time. The Steinbeis team started by optimizing the current measurements used in measuring electrical power for drives fed by power converters. Highly accurate load resistances were developed and tested. Based on the electrical data and mechanical dimensions, these resistances were then adjusted precisely for the Genesis HighSpeed data recorder series produced by HBM. The accuracy of these resistances lies at 0.02% within the relevant frequency range. In addition, analysis methods were developed to define further important parameters for electrical machines and drives. For example, it is now possible to calculate the air-gap torque of a three-phase machine as a time-dependent curve with Perception software using raw current and voltage measurements. The calculated air-gap torque makes it easy to evaluate the dynamic properties and accuracy of the drive control. A demonstration unit was developed to illustrate to interested experts how these measurement methods and analysis processes work. The unit is a complete drive test bench featuring a test and load machine as well as frequency inverters and all necessary sensors. Reducing the weight and size of the unit until it could be checked as airline baggage was quite a challenge. Thanks to the successful collaboration between Steinbeis and the partner company, the product was put on a fast track to new industries and markets. It is this collaboration that has been recognized with the Löhn Award, the Steinbeis Foundation’s Transfer Award. Many of the results of this transfer project have been presented in scientific publications and talks, and they will also be included in the doctoral dissertations of two research fellows at the university. Both partners look forward to further interesting joint projects in future, in the field of efficiency optimization.
Prof. Dr.-Ing. Johannes Teigelkötter
Steinbeis-Transferzentrum Energieeffiziente Leistungselektronik für elektrische Antriebe und Speicher, Aschaffenburg