EMC of automotive inverters
One of the main disturbance sources in the automotive sector is the inverter, used to convert the DC Batterie voltage into 3 phase AC for the motor, e.g. in electric drive systems. During switching operations, the power semiconductors emit disturbance signals in a broad frequency spectrum, which leads to conducted and radiated disturbances. Hence, communication and comforts functions within the vehicle can be affected. Research at the IEH determines methods to minimize disturbance signals directly at its source by using appropriate algorithms and optimized hardware configuration and geometry.
Active and passive filters
Research in the area of filter technology aims to stay within the given limits of international standards or internal standards of OEMs. The challenge in the automotive sector is to find the optimum between the required electric filter characteristics, the minimized additional installation space for the filter and minimized additional costs. Therefore, different approaches are determined: Conventional passive filters can be optimized automatically in terms of their electric requirements, cost and space using different optimization methods like evolutionary algorithms. A new approach considers active filter methods. By using active filters disturbance sources within the inverter can be calculated which allows a prediction of disturbances itself. Hence, suiting phase shifted compensation signals can be injected into the traction network in order to reduce disturbances by superimposition.
Inductive charging systems
Inductive charging is a new challenge for EMC. Power outputs of several kilowatts are transmitted via geometric coils in air without a magnetic core. Therefore, new coupling paths for electromagnetic disturbances emerge during charging as well as in the drive mode of the vehicle. Both, resulting common-mode and differential-mode disturbances can be dangerous for onboard electronics. In order to evaluate the interference potential, the coupling paths are characterized metrological in a laboratory setup and the disturbance variables expected in practice are evaluated. Using FEM simulations models of the inductive systems are developed. Thus, possible disturbances can be estimated already during the engineering process.
EMC of medium voltage installation
In medium voltage switchgears, especially in the distribution grid, low power Instrument transformers/LPITs start to replace common current transformers. Apart from cost advantages, these LPITs offer significant advantages concerning the required space, dynamic range of the measurement, linearity and electric losses. Due to the different measuring principle, propagation paths and levels for electromagnetic disturbances differ from those of conventional current transformers. Therefore, the test procedures given in IEC 60255-26 for protection devices do not fully apply to LPITs. Therefore, research focuses on developing appropriate test procedures in order to guarantee a reliable functioning of protective systems under the influence of all relevant disturbances, for example during switching transients or at high levels of harmonic distortion.
Partial discharge analysis in electromobility
Partial discharges (PD) are a phenomenon within the isolation of different assets. High DC voltage levels and fast transients of the traction inverter in electric vehicles can result in locally increased field strengths, which can promote PD. Regarding the special conditions in traction systems of electric vehicles, the measurement methods and technologies significantly differ from known and established PD measurements used for years in high voltage technologies. The measurement metrologies, the circumstances PD emerge in tractions systems are investigated as well as methods to minimize their occurrence. Resulting measurement setups and simulations provide a risk assessment for manufacturers.
CISPR 25 component level test with complex wiring harnesses
The general complexity of electronic control units in vehicles will increase significantly within the next years: Due to the high safety requirements of both autonomous cars and electromobility the numbers of sensors and actuators build into the vehicle will rise. In order to ensure reliable and reproducible component level tests the soaring complexity of the measurement setup has to be incorporated into CISPR 25; a variety of different bus-signals need to be transmitted between the device under test and peripheral systems using sophisticated wiring harnesses. In this context, the challenge is to find the optimal balance between a realistic component test and an affordable test in terms of time and money. Therefore, the differences between the simultaneous measurement of all bus-signals using an entire wire harness and serialized measurements of similar bus-interfaces using a reduced harness are determined. This approach includes investigations of the influence of complex multi-signal wire harnesses and their arrangement within the CISPR setup with regard to the test reproducibility.