Design parameters for electronic components in a 42 V automotive environment

The last three decades has seen an almost exponential increase in the electrical power requirements of automobiles. Thirty years ago the electrical load of an automobile with an internal combustion engine consisted essentially of the ignition, lighting, direction indicators, dashboard display, windscreen wipers and in a small number of cases perhaps a car radio. Today, by contrast the interior of a modern automobile bears more resemblance to an aircraft cockpit. A modern high-end car has an average electrical load of 2 kW. At present the 14 V system used in automobiles is being taxed to its limits. In the future more power will be needed. To meet this challenge the Consortium on Advanced Automotive Electrical/Electronic Systems and Components at the Massachusetts Institute of Technology was formed in 1994. This group brought together the major automotive manufacturers and suppliers in the world where they agreed on a new 42 V automotive electrical system. The advent of the new 42 V system will also encourage the introduction of new technologies including electronic suspension systems, engine diagnostics and navigational systems. In this paper the standard EMI pulses for 14 V systems are examined with a view to adapting them to 42 V operation. In particular the design issues in components such as relays and motors are examined.