Tag Archives: NVH

Advanced Materials for Magnetic Silence

High-performing advanced magnetic materials are now available that help to handle challenges in hybrid/electrical vehicles. These are challenges related to conducted and radiated electromagnetic interference. Automotive engineers are encountering newer challenges with fully electric vehicles or EVs and hybrid electric vehicles or HEVs become more popular.

The above challenges are so intriguing, engineers now have a fundamental discipline for it, noise vibration and harshness or NVH engineering. Their aim is to minimize NVH for ensuring not only the stability of the vehicle but also the comfort of the passengers.

With electric vehicles becoming quieter, several NVH sources that the noise of the internal combustion engine would mask, are now easily discernible. Engineers divide the root cause of the NVH problems in electric vehicles into vibration, aerodynamic noise, mechanical noise, and electromagnetic noise.

For instance, cabin comfort is adversely affected by electromagnetic noise from auxiliary systems such as the power-steering motor and the air-conditioning system. This can also interfere with the functioning of other subsystems.

Likewise, there is electromagnetic interference from the high-power traction drive system. This interference produces harmonics of the inverter switching and power supply frequencies. Moreover, the interference also induces electromagnetic noise within the motor as well.

With the battery frequently charging and discharging when the EV is in operation, combined with various electromagnetic noises like radiated noise, common-mode noise, and differential noise move through the transmission lines.

All the above reduce the cabin comfort in the vehicle while interfering with systems that help manage the combustion engine in an HEV.

As with many engineering projects, NVH issues are also specific to particular platforms and depend on the design of several structural components, the location of subsystems related to one another, and the design of isolating bushes and mountings. Engineers must deal with most NVH issues related to EMI by applying best practices in electrical engineering for attenuating high-frequency conducted and radiated interference as they couple onto cables and reach various subsystems. Engineers use cable ferrites for preventing long wires from acting as pickups or radiating aerials. They also use inline common-mode chokes for attenuating EMI entering signal and power lines by conduction.

For automotive applications, such cable chokes and ferrites must meet exacting criteria.  Major constraints for these components are their weight and size. Common-mode chokes must provide noise suppression through excellent attenuation properties while using a small physical volume. Additionally, they need to suppress broadband noise up to high operating temperatures, while maintaining high electrical and mechanical stress resistance.

To help with manufacturing such as maintaining high levels of productivity, there are further requirements of robustness and easy handling on assembly lines. This ensures each unit reaches customers in perfect condition. New materials meet the above requirements while offering enhanced characteristics.

The new class of materials is Nanocrystalline cores that engineers classify as metals and they help with eliminating low-frequency electromagnetic noise. Cable ferrites and choke cores made of these materials are much smaller than those made from conventional materials like ceramic ferrites. They also deliver superior magnetic performance, presenting a viable solution for challenging automotive and e-NVH issues.