Lehrstuhl für Elektrische Maschinen und Antriebe

Dr.-Ing. Benjamin Krüger


Rainer-Gruenter-Str. 21

42119 Wuppertal

Raum: FH.01.09


+49 202 439 1867

Persönlicher Werdegang

  • Abitur 2005 in Wuppertal
  • 2005-2011 Studium an der Bergischen Universität, Wuppertal:
  • Bachelor of Electrical Engineering mit den Vertiefungsrichtungen Antriebstechnik und Energieversorgungstechnik. Bachelorthesis im Bereich Automotive.
  • Master Elektrotechnik mit den Vertiefungsrichtungen Leistungselektronik/Hybridantriebe, Smart Grids und Automotive. Masterthesis im Bereich Hybridantriebe.
  • 2011 Ausgezeichnet mit dem Absolventenpreis der Bergischen Universität, Fachbereich E.
  • seit Mai 2011 wissenschaftlicher Mitarbeiter am Lehrstuhl für Elektrische Maschinen und Antriebe an der Bergischen Universität Wuppertal.
  • 2012 Ausgezeichnet mit dem 1. Studienpreis des VDE, Bezirksverein Bergisch Land.
  • 2012 Ausgezeichnet mit dem Förderpreis des VDI, Bergischer Bezirksverein
  • 2020 Promotion zum Dr.-Ing der Elektrotechnik



S. Kratz, B. Krüger, R. Wegener and S. Soter, "Expansion of a Trolleybus Infrastructure towards a 100{%} Renewable Energy Usage" in 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC), 2021, pp. 0233--0236.

The german government furthers a research project targeting the full electrification of the largest trolleybus network in Germany in prospect of deriving a pilot scheme for major cities. Based on the good interim results, another near future aim arised: operation of the trolleybus network with 100{%} renewable energy. To achieve this, the large-scale integration of photovoltaic arrays in combination with second life bus batteries into the network is planned. This paper presents the actual status of the research project and the already closed steps towards the aim. It presents measurement results of the developed hardware from the laboratory and the last adaptations for field testing. Overall the measurements show a high efficient integration of photovoltaics and batteries which leads to a positive prediction regarding the aim with an integration and interaction in large-scale.
D. Maune, B. Krüger, P. Sahm and S. Soter, "Speed Control for Lifting Devices with Conical Cable Drum through Indirect Position Determination" in 2020 IEEE International Conference on Industrial Technology (ICIT), 2020, pp. 401--405.

Lifting devices are often provided with a spring to compensate their constant weights. But because the force of a spring is depending on its stretch, the compensation ratio during a lifting process is fluctuating. By changing the characteristic of the load with the help of a variable radius drum it is possible to mitigate this drawback. In this paper a torsion spring and a conical cable drum are used for compensation. Because the wound cable length per revolution is changing, the lifting speed also varies. For the introduced speed controller the position of the drum is measured with an absolute, magnetic sensor. The actual lifting speed is then indirectly determined by calculation utilizing the cable drum parameters.
S. Kratz, P. Hanses, B. Krüger, R. Wegener and S. Soter, "Integration of Second Life Batteries into a Smart Overhead Contact System based on SiC-Technology" in 2019 IEEE Transportation Electrification Conference and Expo (ITEC), 2019, pp. 1--5.

This paper presents the starting situation and some interim results of a research project with the aim of a fully electrified short-range public transportation in a German town called Solingen. It gives an insight to the existing trolleybus infrastructure and the benefits of second life battery usage. Following, the design configuration of a refurbished trolleybus battery system for stationary usage in substations is shown and evaluated. Based on this a new silicone carbide power electronic for a direct integration of stationary battery systems are proposed and evaluated. Available semiconductors for the prototype are specified and compared by measurements. The results show that the integration of trolleybus batteries can be done with high system efficiency.
S. Kratz, A. Schmidt, B. Krüger, R. Wegener and S. Soter, "Power Supply of a Short-Range Public Transportation System Based on Photovoltaics - Potential Analysis and Implementation" in 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), 2019, pp. 3077--3081.

This paper answers the question of if an existing short-range public transportation system in a German town called Solingen could be exclusively supplied by photovoltaics and presents a fitted device for energy conversion. Based on the results of the proposed method for a photovoltaic potential analysis, the above question is answered and the main benefits of the direct integration of photovoltaic arrays are shown. The presented measurements of a 10kW prototype show that a high conversion efficiency can be achieved.
B. Krüger, S. Kratz, T. Theopold and S. Soter, "Wear Reduction Control Method in a Blade Pitch System of Wind Turbines" in 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE), 2019, pp. 1107--1112.

Mechanical transformation of speed is needed in a lot of industrial applications but it is attended by backlash. Gear parts without closed linkage can accelerate and crash to another. So with the backlash comes the wear. There are many technical solutions and ideas to reduce the backlash by mechanical and electrical components and adaptions, but in most cases with the goal to increase the precision. In some applications, like the described pitch drive, the precision is not the problem and the increasing costs for backlash elimination are not to justified because the reduction of wear is more important. Further the extensive adaption has influence on functional safety and maintenance. This paper gives a short overview of mechanisms that reduce the wear in a given application without mechanical adaptions, only by adding a software module. In the first step backlash is detected and in dependence on its reason in a second step a reaction is induced by the drive to spare the mechanics.
S. Kratz, B. Krüger, R. Wegener and S. Soter, "Integration of Photovoltaics into a Smart Trolley System Based on SiC-Technology" in 2018 IEEE 7th International Conference on Power and Energy (PECon), 2018, pp. 168--173.

This paper gives an insight to a research project with the aim of a fully electrified short-range public transportation in a German town called Solingen. It starts with an overview of the special characteristics of the existing fully isolated overhead contact system and then derives the projected system. A new silicone carbide power electronic and the necessary control algorithms for the direct integration of photovoltaic arrays are proposed and evaluated. The measurement of a first small volume 10kW prototype inverter shows that the integration can be done with high efficiency.
F. Senicar, M. Döpker, A. Bartsch, B. Krüger and S. Soter, "Inverter based method for measurement of PMSM machine parameters based on the elimination of power stage characteristics" in IECON 2014 - 40th Annual Conference of the IEEE Industrial Electronics Society, 2014, pp. 702--708.

This paper presents the precise measurement of the stator inductance as well as the stator resistance, using an inverter. Precise measurement results are created, although the actual output voltage of the inverter is not known exactly. This paper analyzes the different effects of an output power stage, and how they degrade the quality of the output voltage. This knowledge is used to cancel out this output voltage error in enabling a precise measurement of the machine parameters. This allows an easy auto commissioning of the current controller and furthermore an auto commissioning of an optimal torque control. The presented methods are verified with extensive measurement results.
B. Krüger, S. Gruber and S. Soter, "Controlling of medium voltage power-factor of photovoltaic power plants from the low voltage side" in 2013 IEEE Energy Conversion Congress and Exposition, 2013, pp. 569--574.

The effort to make the production of electrical energy much more environmental-friendly, large conventional power plants will be replaced by several smaller regenerative power plants. In order to improve stability and controllability, these smaller power plants are supposed to control the active power, the reactive power and the power factor in the medium voltage grid like conventional power plants. This paper will discuss three different methods to control the medium-voltage power factor from the low voltage side in consideration of parasitic effects from cables and transformers to fulfill the guidelines at the grid connection point. A method with a self-learning-algorithm will be implemented and proven by simulations and measurements on a test bench with inverter and 400 V to 10 kV grid transformer. The self-learning-algorithm will give the opportunity to reach every required power factor at the grid connection point.
S. Gruber, B. Krüger and S. Soter, "High force tubular linear actuator with integrated eddy current brake for spring-loaded systems" in 2013 IEEE AFRICON, 2013, pp. 1--5.

In order to meet safety standards in manufacturing industry many production machines are equipped with safety stop functions based on spring-loaded systems. This paper deals with an integrated eddy current brake of a high force tubular permanent magnet linear actuator for hydraulic applications with small actuating pathes. An analytical description of different design criteria for the integrated eddy current brake are shown. The special not rotational symmetrical design of the tubular linear actuator is transferred to a 2D transient FEM simulation model to predict the braking behavior caused by the spring load in case of an emergency stop. Measurements on a test bench are in good agreement with the simulation results and are used to validate the model.
F. Senicar, A. Bartsch, B. Krüger and S. Soter, "Enhanced bandwidth current controller for FPGA based inverter drives - a detailed analysis and implementation" in IECON 2012 - 38th Annual Conference of the IEEE Industrial Electronics Society, 2012, pp. 1775--1780.

This paper presents the optimization of the current control loop implemented in a field programmable gate array (FPGA) based inverter. The bandwidth of the current controller is significantly enhanced by reducing the delay times to its theoretical minimum. The optimizations are at first analyzed on a theoretical basis and afterwards verified on the actual target system. It is discussed, that the optimized current controller can be implemented without any drawbacks in terms of available output voltage. It is shown, that the significant reduction of delay times can be implemented in practice, greatly enhancing the bandwidth of the current controller, thus allowing a much higher controller gain.

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