Mechanical Reliability in Dynamic Heating Applications

In a joint development project, PACK LitzWire worked with an automotive customer to optimize flexible conductors used as heating elements in seats, steering wheels, and armrests. These conductors had to reliably withstand extreme mechanical stresses, continuous bending cycles, and temperature cycles over the entire vehicle lifetime.

The Challenge

Since these are low-frequency or DC heating applications, the focus was less on high-frequency electrical losses and more on mechanical and reliability aspects.

• Mechanics: The heating conductors were subjected to continuous bending cycle loads in seat structures and steering wheels. Partial breaks of individual strands could have led to locally increased resistance and thus to potential hot spots.
• Corrosion: Moisture and cleaning agents in the interior could increase the risk of contact or galvanic corrosion and had to be prevented by suitable material selection.
• Resistance Consistency: For uniform heating, precise and stable conductor resistance was required over the entire length.

Support from PACK LitzWire

PACK LitzWire contributed its expertise in mechanics, material selection, and reliability, working closely with the customer's development engineers.

• Mechanical Design: Together, lay lengths, lay directions, and litz wire bundling were optimized to achieve maximum continuous bending strength and flexibility.
• Connection Technology: PACK LitzWire advised on the selection of suitable contacting methods (crimping vs. welding), as transition resistances at the connection points represent critical sources of error.
• Material & Standard Consulting: The appropriate insulation class and material resistance were selected based on relevant automotive requirements, including resistance to moisture, temperature, and cleaning agents.

Result

Through the coordinated adaptation of stranding parameters and material selection and design, a litz wire construction was created that significantly exceeded the required bending cycle resistance. The robust insulation reliably prevented corrosion and ensured long-term stable heating performance – enabling the customer to implement a highly reliable, durable solution for the vehicle interior.