HV applications place very high demands on the material, the individual components and the overall system, which can only be achieved, among other things, through appropriate material selection, design decisions during construction, clearances of the air and creepage distances or additional insulation.
Just as much attention is paid to the insulation level of the application and here a simple electrical connection becomes a real challenge: The parallel connection of several components in the vehicle.
In electric vehicles, the individual components are connected in parallel with the HV battery. This means that as the number of HV components increases, the insulation resistance of the overall system decreases. Remember: The resistance of the overall system of a parallel circuit is always smaller than the smallest individual resistance and this also applies to the insulation resistances in electric vehicles.
For the reasons mentioned above, vehicle manufacturers have a great interest in ensuring that the HV components from the suppliers each have a very high insulation resistance. This requirement is reflected in the factory standards of the respective vehicle manufacturers mentioned previously. Insulation resistances in the three-digit mega-ohm range are required for the tests within the scope of the service life qualifications of the manufactured HV components. This does not refer to the test result after production, but to the entire planned life cycle of 15 years.
In addition to the parallel connection of the individual components, there is also material wear and tear, moisture penetration, contamination and corrosion throughout the entire service life of an electric vehicle. Therefore, the vehicles must have much higher insulation values when delivered in order to function safely for a long time. Insulation values of up to 10 GΩ (gigohms) are therefore not uncommon. With regard to later maintenance work, it is of interest to know exactly the insulation value of the components or the entire vehicle as delivered, because only then can measured insulation values be correctly evaluated within the life cycle during inspections.
The manufacturers of HV components must therefore test how the products behave during development in order to be able to guarantee the required values over the entire service life. High-voltage tests must be carried out by trained personnel, and this very often results in the interruption of long-term tests. This costs time and money. With the insulation monitoring devices ISOMETER® of the types isoHR685 and isoHR1685, Bender now offers a solution with which these high-impedance insulation values can be monitored continuously during development.
The demand for very high insulation values and continuous monitoring of insulation values automatically leads to the fact that previously used test benches and laboratory equipment of the supplier industry as well as the test houses have to be modified or retrofitted and completely redesigned in terms of measurement technology.