With the increasing spread of high-voltage technology in e-mobility, new problem areas are emerging that automotive manufacturers (OEMs) and suppliers were previously unaware of. This is because phenomena such as sliding discharges do not occur at operating voltages below 100V (12VDC, 24VDC and 48VDC). However, above 400VAC, partial discharges can lead to problems that were previously unknown in automotive engineering.
In addition to the high stress caused by the electric field strength, there are other influences in the vehicle such as heat, vibration, humidity and climate change. All of this can lead to medium or long-term failures if the insulating materials used are not considered correctly. The DC/DC converter, electric motor and battery charging unit or frequency converter (rectifier) for motor control are particularly affected.
Background: The dielectric strength of an insulating material is usually considered in an electric field that is largely perpendicular to the material. However, at feedthroughs through earthed housing parts or other abrupt transitions, for example, the electric field can develop tangentially, i.e. along the surface of an insulating material. This interface often has a significantly lower electrical strength than the insulator itself. This lower breakdown voltage can have an effect on the insulating material.
Due to the lower electrical strength of the interface, high-energy ignitions of discharges can occur considerably earlier. These lead to erosion of the insulating material surface and ultimately to its failure. The simplest measure against the formation of conductive paths is, of course, to design the geometry generously. This is because distance reduces the field strength and prevents sliding discharges. However, this contradicts today's desire for compactness.
In addition to the use of materials that are more resistant to this type of destruction by sliding discharges (e.g. good cti value or high content of inorganic fillers), field control can be achieved with semiconducting products. This field control can be resistive and/or capacitive.
CMC Klebetechnik offers semi-conductive products (e.g. semiconductor crepe) for the "smooth" transition and for directing the electrical field, with which sliding discharges can be avoided. Alternatively, insulation tapes with high partial discharge resistance can also be used in compact designs where there is no space for semi-conductive coatings. These are, for example, adhesive tapes from the CMC 27xxx product range, which have a cti value = 0 and therefore very good resistance to the formation of sliding discharge paths. Or Kapton® CR and Kapton® MT can be used, for example, both of which have increased resistance to corona due to their inorganic filling. Alternatively, Kapton® FN can also be used, whose fluoropolymer coating significantly increases the partial discharge resistance.
All products can be supplied self-adhesive on one side. Die-cut parts and customized rolls are also possible. Even the coating of thermally conductive adhesive instead of the usual PSA can be offered for corresponding quantities.
Due to the lower electrical strength of the interface, high-energy ignitions of discharges can occur considerably earlier. These lead to erosion of the insulating material surface and ultimately to its failure. The simplest measure against the formation of conductive paths is, of course, to design the geometry generously. This is because distance reduces the field strength and prevents sliding discharges. However, this contradicts today's desire for compactness.
In addition to the use of materials that are more resistant to this type of destruction by sliding discharges (e.g. good cti value or high content of inorganic fillers), field control can be achieved with semiconducting products. This field control can be resistive and/or capacitive.
CMC Klebetechnik offers semi-conductive products (e.g. semiconductor crepe) for the "smooth" transition and for directing the electrical field, with which sliding discharges can be avoided. Alternatively, insulation tapes with high partial discharge resistance can also be used in compact designs where there is no space for semi-conductive coatings. These are, for example, adhesive tapes from the CMC 27xxx product range, which have a cti value = 0 and therefore very good resistance to the formation of sliding discharge paths. Or you can use, for example Kapton® CR and Kapton® MTboth of which have increased corona resistance due to their filling with inorganic materials. Alternatively, Kapton® FN can also be used, whose fluoropolymer coating significantly increases the partial discharge resistance.
All products can be supplied self-adhesive on one side. Die-cut parts and customized rolls are also possible. Even the coating of thermally conductive adhesive instead of the usual PSA can be offered for corresponding quantities.
High-voltage applications: Weak point interfaces