Improvement of the correlation between ALSE and BCI by adjusting the feeding and positioning conditions based on indirect measurement of termination impedances using current transformers

Abstract

The most commonly used automotive immunity test methods for electrical interferences from narrowband radiated electromagnetic energy are described in ISO 11452 series. Bulk Current Injection (BCI) and Absorber Line Shielded Enclosure (ALSE) apply different coupling mechanisms to assess the immunity of electronic components. While ALSE subjects the entire test setup to the electromagnetic fields generated by an antenna, BCI induces the interference signals directly into a certain part of the wiring harness by a current injection probe. ALSE is often considered as the more reliable method. However, testing with BCI is preferred as it allows performing the immunity tests in less time with less effort and cost. Despite using similar test setups, different interference currents are injected into the terminal units at each test method and therefore, the correlation between the test results is often poor. In order to improve the correlation, the BCI method must be modified to inject the same interference current as the ALSE method. This thesis proposes an approach that searches for these modifications and makes it possible to inject the same interference currents with a BCI probe. The two main issues of concern are the calculation of the injected interference currents during real test scenarios in a simulation environment and, the measurement of the input impedance of terminal units under the operation condition using optimized current transformers. The developed models and measurement methods are combined to reproduce the ALSE currents with a single BCI probe. In line with the implementation scheme: firstly, a measurement-based approach to model the ALSE and BCI couplings to a wire-over-ground structure is developed. These models are used to determine the interference currents at the terminal units; secondly, theoretical and measurement based methods are developed to characterize current transformers. The goal is to assess the ability of a current transformer to measure the input impedance of the terminal units without disconnecting the wiring harness; thirdly, four non-invasive methods to measure the input impedance of terminal units using optimized current transformers are proposed and experimentally validated; finally, an approach to reproduce the ALSE termination currents with a single BCI probe according to an optimization process is developed and validated. Capabilities and limitations of the proposed methods and approaches are analyzed, discussed, and ultimately applied to a real immunity test setup.