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Plastic cover gives inverter e-Traction quality appearance

The choice of plastic can be for an economic reason; a plastic part is often cheap to produce. But this does not mean that the value is any less. In fact, on the plastic top cover of the inverter of the in-wheel electric motor of e-Traction, the company logo proudly shines. “It contributes to the quality appearance of our complete system,” says the producer.

The plastic top cover is one of the three injection-molding parts that Alligator Plastics creates for e-Traction. The cover protects the electronics on the inverter, which forms the heart of the in-wheel electric motor. Alligator Plastics also produces the bus bar mounting-base (a holder for plugs), and a compression ring as the seal for the inverter. All parts are made of the plastic PBT. This polymer has a high temperature- and chemical resistance, and good impact strength. The PBT is 30% glass fiber.


There was almost a year between the first drawings and the fabrication of the three plastic parts. This signifies the great care with which the parts are developed and tested. This amount of time is nothing compared to the number of years e-Traction took to develop their revolutionary in-wheel motor system. The originally Dutch company, now in Chinese hands, has been working on the innovation since 1981. The system, called TheMotion, is an electric drive where an electric motor is placed in each rear wheel. The drive is, of course, emission-free and carries the energy from battery to wheel very efficiently. In addition, a conventional driveline, with a differential and gears, is no longer necessary, allowing the driveline to have less p0wer loss, and therefore be cheaper to use. The current design of TheMotion is suitable for all vehicles with a 22.5-inch tire, such as buses and trucks.

Alternative to aluminum

With the first version of the system, e-Traction already put down a proof of concept. In 2008, an improved version was mounted under a small series of buses. Currently, the company is working on the latest version, which should be ready for production in 2019. “For the new version, we were looking for a cheap alternative to aluminum casings,” says buyer, Kye Ellen Breedijk, from E-traction in Apeldoorn. “The choice for a plastic injection-molding solution was quickly made. During the selection of our injection-molding partner, Alligator Plastics responded very quickly to our questions. There, where our knowledge of plastics and injection-molding fell short, they supplied that knowledge perfectly. Ultimately, they came up with an optimum design with minimum use of materials. The parts are economically and ecologically responsible.”

From basic design to manufacturable product

“Our added value was mainly in the ability to facilitate the manufacturing of the product,” says project leader Jordi Torres, of Alligator Plastics. “The customer already had a basic design for the top cover and the other two parts. We have optimized the design through, among others, savings on materials and minimization of wall-thickness. To be able to make the product suitable for injection-molding, we came up with clever solutions (corners to the product), so that they can easily come out of the mold. We recommended PBT as the plastic material to be used. This material complies with all the requirements of e-Traction and is available at an acceptable cost.”

e-traction top cover

Intensive collaboration

“During the development, the engineers at e-Traction and our engineers worked closely together,” says sales manager, Paul van den Broek, of Alligator Plastics. “They may be relatively cheap plastic components, but they protect the critical electronics in the inverter. Both teams gave the design a lot of attention. We made small steps along the way to fine-tune and test the products. This is why the process took a full year.” According to Kyu Ellen Breedijk of e-Traction, there was another reason why the injection-molding products deserved all the attention: “The top cover is an important product. It is the visible top of the inverter, which contains our logo. Such an important system component needs to look good. It contributes to the overall quality-appearance of our system.” According to Kyu Ellen, e-Traction is already working on the next innovation in the automotive business: “With this new development, we would like to bring in partners who we are satisfied with. And I can tell you: we are very satisfied with Alligator Plastics.”

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