Interview: New high-voltage production for wiring harnesses for electric cars

Delphi, Interview with Dipl. Ing. Edmund Erich, (engineer): Development Manager for E-Mobility Systems at Delphi‘s E/E Architecture Division, EMEA, Delphi Deutschland GmbH.

Mr Erich, Delphi has started production of high-voltage wiring systems for a German electric car. How does the production of wiring harnesses for high-voltage drive mechanisms differ from the usual 12 V networks?

Edmund Erich: The differences derive from the product, which, although it is a lead, is very different in terms of structure and dimensions. That’s why the production process and the equipment had to be adapted to the quality assurance requirements and employees had to be given special training. Here’s one example: the number of leads may look modest enough, but it is the more complex layout of the leads that makes it much more difficult to assemble the leads when producing a wiring system like this. Thus, it is not just a cable’s conductor, but also its shielding that has to be joined precisely, securely and reliably with other components. This involves several precisely defined steps – many more than in a 12 Volt lead. These changes to a long-standing process forced us to focus on the training of our wiring system assembly staff.

A new assembly line was established?

Erich: That’s right. We have set up a new assembly line for high-voltage wiring systems in EMEA. The staff there has received special training. This requires very well trained personnel, as distinct from the usual production of cable components and harnesses practiced by us to date around the world. Our high-voltage production staff also wears a special uniform, distinguishing them from their colleagues, so that they enjoy particular respect in the plant. The preparations took place at our Customer Technology Centre in Wuppertal. That’s where we first set up a high-voltage production line in close cooperation with Development, enabling us to gather practical experience for when batch production was eventually ramped up to full-scale output.

Is it possible to gather more information than computer simulations can provide?

Erich: Certainly. I can’t go into detail here, but the extremely high quality requirements mean that every tiny detail, however insignificant it may seem, must be examined in terms of its impact on production. Of particular importance – and here I would like to focus on the human factor – is the safe handling of high-voltage technology. After all, the finished products have to be tested under load at the end of the production line. The layout and design of the testing area must meet the requirements of an efficient process and offer the greatest possible protection against incorrect handling of the components when under load.

So, the human factor is an important element in wiring system production?

Erich: That’s right. We have very highly qualified staff in our plants. Together with them we have come up with the best possible production process. Above all this required that all those involved should be made aware of the importance of correctly handling the processed materials. The copper wire in a high-voltage lead is much larger and is also enclosed in a sheath like an antenna cable. This is important for shielding purposes. Every manual intervention has to be just right. Repairs are not possible. A single mistake can mean a considerable loss. As already mentioned, the copper conductor is not as thin as in a 12 Volt cable. If a lead is connected incorrectly in a low-voltage wiring harness, the problem can be resolved using a special tool once the fault has been detected. This is not possible with a high voltage wiring system.

What challenges did you have to resolve for the machine fleet?

Erich: In general we had to adjust the machines and all the equipment to enable wires of larger diameter to be processed. I can’t go into detail here, but cutting proved to be a central challenge. This is because stronger forces are required, while still remembering to handle the material gently to ensure 100% shielding and insulation. In view of the high levels of power carried by the leads and potential of up to 600 Volt, insulation is a key concern. Stripping of wires is a mechanical process and, in order to ensure fast, efficient production, we had to find a mechanical solution that was a bit like squaring a circle.

You might say that maximum precision and absolute quality in handling a high-tech product are part of your daily routine?
Erich: Yes, but I have significantly fewer leads in the electric cars. However, every lead has its specific problems. That’s because every lead requires an extremely complicated production method. Every step has to be carried out with extreme precision.

Thank you for the interview Mr. Erik.

www.delphi.com

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