Coroplast is one of the pioneers in the development and integration of high voltage and charging power cables for the area of hybrid- and electrically powered vehicles. The development of the high voltage cables product range began in 2006. The delivery of the first serial products to well-known German auto manufacturers took place for the first time in 2009.
In this early stage, in collaboration with German auto manufacturers, Coroplast provided the necessary technical support and still participates in the basic development to this day, with the aim of developing technical standards in the field of high voltage cables. The basic specification requirements, and therefore the currently valid standards, can now be found in the national technical delivery specifications, LV 216-1 “Unshielded high voltage individual cables for vehicles and their electrical drives” and LV 216-2 “Shielded high voltage sheathed cables for vehicles and their electrical drives.” These technical delivery specifications were developed together by the five German auto manufacturers.
The fitting of HV cables in electrical systems for hybrid and electric vehicles necessitates high safety requirements in the area of the construction of these cables and the materials that are used.
In the traction strand, for example, current voltages of 600 VAC / 900 VDC have to be transferred between the high voltage battery, the power electronics and the electrical motor. Prototype cables are already available from Coroplast for the testing of the upcoming voltage class of 1,000 VAC / 1,500 VDC. Cable cross-sections of 10 mm² to 70 mm² enable continuous currents of up to 450 Amperes, depending on the environmental temperature.
In their operational state, due to the use of high quality modified silicone materials, Coroplast HV-cables are able to realise long-term temperatures of up to 180°C. This material also enables the realisation of the demanding sealing requirements (e.g. IP69 K) of HV contacts due to its excellent compression deformation values in combination with talc-free surfaces. Due to limited construction space and the high level of flexibility required when fitting the cables, single-core shielded cables are used here, which are fitted in parallel.
Supply cables for ancillary components such as the electrical air conditioning system, are multi-core shielded. These multi-core shielded cables are equipped with a specialist gap-filler at Coroplast. This filler fits itself around the electrical wires without an air cushion, and therefore enables an optimised heat dissipation when the current is supplied, and furthermore ensures a production-friendly, circular application of the shielding.
A round shielding geometry, the omitting of a film as a geometrical support, cut-space due to the filling layer, and the omitting of filling threads that have to be removed manually all mean huge advantages in the production of these cables.
High EMC requirements with shielding attenuations of up to 70 dB and resistance coverings with up to max. 3 m/m require special cable constructions in the area of the mesh wire braid (conductor design, angle of twist, visual cover).
The reduction of weight and the minimisation of costs through the substitution of the copper wiring with aluminium (lower material density / lower material prices) represents a consistent and necessary task with the development of hybrid and electrical vehicles in particular. Due to its lower electrical conductivity and current-carrying capacity in comparison with copper, larger conductor cross-sections have to be used, which also lead to bigger external diameters. The use of aluminium as a cabling material also affects the contacting and/or connection technology. As aluminium creeps at high temperatures (retardation), it changes its shape when under pressure in the micrometer range. Classic crimp connections, such as those that are standard with copper cables, are no longer reliable. New connection procedures, such as ultrasound welding, are now being used. In this field, Coroplast is working with well-known manufactures of ultrasound welding systems for the purpose of attaining a possible optimisation of the conductor designs and conductor materials.
