VIENNA—When it comes to automotive solutions, it can be the smallest part that makes the biggest difference.
Freudenberg Sealing Technologies believes it has those big-difference-making parts, unveiling a new generation of conductive seals for electric drivetrains at the 2021 Vienna Motor Symposium. Marketed under the eCON name, the new seals are designed to prevent bearing damage caused by electrically induced corrosion, while increasing electromagnetic compatibility.
"The electrically conductive seal is a small, inconspicuous component, but its impact is enormous" Stefan Morgenstern, advance developer at Freudenberg, said in a statement.
Electric drive systems that operate at 800 volts instead of the normal 400 volts have a 15-minute recharge time and a several hundred mile range, Freudenberg said in a news release. The power semiconductors used in the inverters ensure the direct current stored in the battery is properly converted into an alternating current that is needed by the motor while driving.
Vehicles made with the 800-volt drive trains often use silicon carbide semiconductors. These semiconductors can switch high currents as many as 20,000 times per second, and each switch causes slight voltage fluctuations.
Without proper modification the result of these fluctuations can have two unwanted consequences, Freudenberg said:
- the rotor shaft functions as a rod antenna and radiates electromagnetic interferences; and
- excess voltage may build around the vehicle's electrically insulated rotor shaft, overtaxing its ability to discharge and thus discharging instead through the shaft bearings.
"We can eliminate unwanted side effects from electric drives with power semiconductors made of silicon carbide," Morgenstern said. "As a result, the seal contributes to the ultra-fast charging of electric cars, and ultimately, to faster acceptance of electric mobility as a whole."
To achieve these results, Freudenberg said it used "a very thin, conductive nonwoven material," attaching it to the radial shaft seal ring. This allows for direct electrical contact between the rotor shaft and motor housing.
"The development of a new material blend now makes it possible to use a nonwoven with the very low AC resistance of about one ohm," the company said. "As a result, the electrical conductivity of the nonwoven material is high enough not only to prevent electro corrosion but also the emission of electromagnetic waves."
