Freudenberg develops new generation of conductive seals for electric drives

According to foreign media reports, Freudenberg Sealing Technologies (FST) has launched a new generation of conductive seals. The seal, called "eCONevo", can prevent bearing damage caused by electrical corrosion and improve electromagnetic compatibility, which is said to be of great significance for high-performance electric drive devices.

(Image source: FST)

The company says that electric vehicles with an 800V drive system (instead of the traditional 400V) can be fully charged in just 15 minutes and generate enough power to travel hundreds of kilometers. During driving, the direct current in the battery is converted into the alternating current required by the motor through power semiconductor components in the inverter. These power electronic components are usually located just above the motor and are also called motor injection systems. Now, a new generation of semiconductor components made of silicon carbide are increasingly used in 800V drives, as well as other electric and hybrid drives. These silicon carbide semiconductor components can convert high currents 20,000 times per second. Each conversion process can cause slight voltage fluctuations, with an overshoot frequency of 1 or 2 megahertz, which is within the range of medium wave radio.

If not adjusted, these frequencies can be transferred to the rotor shaft of the electric drive and have undesirable side effects in two ways: the rotor shaft acts as a rod antenna and radiates electromagnetic interference, and overvoltages can build up around the vehicle's electrically insulated rotor shaft, overtaxing its discharge capacity, causing it to discharge through the bearings. This destructive effect is called galvanic corrosion and can reduce the performance and life of the bearings.

Freudenberg Sealing Technologies says its new generation of conductive seals is designed to eliminate both of these effects. eCONevo is a very thin conductive nonwoven material that is attached to the radial shaft seal ring and provides direct electrical contact between the rotor shaft and the motor housing.

FST said that thanks to a new material mixture developed, they can use a non-woven material with very low AC resistance (about 1 ohm). This material has a high conductivity, which not only prevents electrical corrosion, but also prevents the generation of electromagnetic waves. According to reports, this non-woven material is about 1mm thick and usually does not require changes to the engine design. Moreover, this material can be tightly attached to the radial shaft seal without additional steps when assembling the motor. This component prevents the motor from being directly exposed to electromagnetic interference, so it can replace expensive shielding layers on other areas (such as the drive shaft).

FST has verified the effectiveness of the seal on a self-developed test bench that tests electric motor components at speeds of up to 36,000 RPM. Series production of the seal is expected to begin in the coming months. "With the new seal, we can eliminate the undesirable side effects of silicon carbide power semiconductor components on electric drives. As a result, the seal helps to achieve ultra-fast charging of electric vehicles and promotes the development of electric mobility as a whole," said Morgenstern, a senior developer at the company.