The desire to reduce energy consumption in industry, domestic use, and road traffic, is placing more demands on the energy efficiency of electric drives and motors. To really understand how well attempts to optimize the efficiency of electric machines and convertors actually work, accurate measurement devices are needed, as well as the right measurement techniques and analytical procedures. Motivated by strict customer requirements from businesses and the need to simultaneously capture and process electrical and mechanical measurements in real time, the Steinbeis Transfer Center for Energy-efficient Power Electronics for Electrical Drives and Power Storage Systems, which is based at Aschaffenburg University of Applied Sciences, has been working in collaboration with the Darmstadt-based measurement technology company HBM (Hottinger Baldwin Messtechnik GmbH) to define the specifications required for measurement devices and data analysis, and to then implement these in practice. The two partners received the Steinbeis Foundation Transfer Award for their raw data analysis and the accuracy of the efficiency measurements taken on electric drives.
To ensure that energy efficiency measurements match actual applications and generate meaningful results, the experts used a measurement model based on time-varying load points. The team first optimized the electric current measurements that are used to gauge the electrical output of rectified drives. 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.
The experts also came up with analysis methods to determine other important parameters for electrical machines and drives. For example, using software called Perception, it is now possible to calculate the airgap torque in rotating field machines. This is done with raw data measurements of currents and voltages, and these are plotted on graphs over time. Calculating when there are air gaps makes it easy to assess the dynamic properties and the accuracy of drive controls.
To explain and illustrate the measurement techniques and different analytical methods to experts, the team built a demonstration unit. This consists of a complete drive test bench with a testing and load unit, frequency inverters, and a complete array of sensors. One challenge was to minimize the weight and size of the demonstration device so that it could be checked as airline baggage.
The success of the collaboration was recognized by the Steinbeis Foundation’s transfer award – the Lohn Award – and this provided a stepping stone to a new sector of industry and new markets. Some of the results of the transfer project have been shared in scientific publications and presented in speeches. They also form the basis of two doctoral studies being conducted by research assistants at the university. Both of the project partners anticipate further interesting project ideas in the field of efficiency improvement.
Professor Dr.-Ing. Johannes Teigelkotter
Steinbeis Transfer Center Energy-efficient power electronics for electrical drives and power storage systems (Aschaffenburg)