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Seals prevent bearing damage in EVs

Freudenberg Sealing Technologies’ new generation electrically conductive seals prevent bearing damage caused by electrically induced corrosion, and also increase electromagnetic compatibility. Electric cars with drive systems that operate at 800 volts instead of the usual 400 can recharge in just 15 minutes, and produce enough power to drive several hundred kilometers. The power semiconductors in the inverter ensure that the direct current stored in the battery is converted into the alternating current required by the electric motor while driving. These power electronics are often positioned directly above the electric motor, and are also known as electric engine injection systems.

A new generation of semiconductors made from silicon carbide is being increasingly used for 800-volt drives, as well as in other electric and hybrid drives. These silicon carbide semiconductors switch high currents up to 20,000 times per second. Each of the switching processes causes slight voltage fluctuations. The frequency of these overshoots is one or two megahertz, which puts it in the range of medium-wave radios. If left unmodified, this frequency is transferred to the rotor shaft of the electric drive and results in two undesired side effects: The rotor shaft functions as a rod antenna and radiates electromagnetic interferences; and excess voltage can potentially build around the vehicle’s electrically insulated rotor shaft, overtaxing its ability to discharge, and thus discharging instead through the shaft bearings. This damaging effect is known as electro corrosion and reduces the performance and life cycle of bearings.

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