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Standards for New 42-Volt Automotive Systems Under Way

New Subcommittee D09.42 on 42-Volt Insulating Materials will develop standards addressing the automotive industry's upgrade to 42-volt electrical systems in new models. The upgrade will apply to domestic and foreign vehicles, replacing 12-volt operating systems. The subcommittee welcomes stakeholders to develop these standards, especially automotive component manufacturers and plastics suppliers.

“The automotive industry is making a transition in design from 14-volt to 42-volt electrification systems,” explains subcommittee member John S. Stimitz, manager, CAS III Automotive Sector, Underwriters Laboratories Inc., Melville, N.Y. “Components that currently operate through inefficient mechanical and hydraulic systems such as air conditioning, water pumps, oil pumps, heating, and solenoid-operated engine valves will be replaced by electric and electronic systems. The increased demands on the automotive electrical systems require upgrading from the traditional 12-V DC battery supply to a 36-V DC battery supply with a nominal 42-V DC charging circuit.”

The new subcommittee is part of ASTM Committee D09 on Electrical and Electronic Insulating Materials. It will develop standards for pre-selection tests for road-vehicle applications used by plastic and component manufacturers specializing in transportation materials. The subcommittee invites individuals to join its standard development activities for electrical and insulating materials used in 42-volt systems.

Stimitz describes key issues regarding the 42-volt increase. “Safety and the potential risk of fire is a concern in view of the increase in voltage to 42 volts DC,” he explains. “Arcing at relays, switches and connections is a very big concern. When a switch opens at 14 volts, there is relatively no arc present. However, at 42 volts, the arc is more pronounced and the potential for fire has significantly increased. Therefore, it is important that standardized pre-selection tests be developed in order to appropriately select materials for use in applications where the potential for arcing exists.”

The subcommittee will initially draft a DC Comparative Tracking Index Test. “The purpose of this test is to determine the susceptibility of the test material to resist or form a visible carbonized conducting path over its surface when subjected to DC voltages,” says Stimitz. “This new test method is similar to ASTM D 3638 [Standard Test Method for Comparative Tracking Index of Electrical Insulating Material] except for changes in the electrical voltage source and the aqueous contaminant based on automotive needs.”

The subcommittee also plans to develop a DC High-Current Arc Ignition Test. “The purpose of this test is to differentiate materials with regard to resistance to ignition from a DC High-Current Arc Ignition source. It is similar to the test specified in UL 746A except for the change to a DC electrical supply source and other special modifications currently being developed,” he says.

For further technical information, contact John S. Stimitz, manager, CAS III Automotive Sector, Underwriters Laboratories Inc., Melville, N.Y. (phone: 631/271-6200, ext. 22214). Committee D09 meets March 17-19 in Kansas City, Mo., and Oct. 20-22 in Tampa, Fla. For meeting or membership details, contact Christi Sierk, manager, Technical Committee Operations, ASTM International (610/832-9728). //

Copyright 2003, ASTM