The 42 V discussion that started 10 years ago was prompted by the belief that there would be an increased power demand in the future. The belief was that the power demand would reach at least 3 kW (in some vehicles up to 5 kW), and that it could not be sourced by a 12 V net. Although a silent majority did not support these arguments, they are still influential. Nevertheless, the maximum power in a 12 V net increased from 1,5 kW in the beginning of the nineties to 3 kW realized today. And there are still opportunities identified in the think tanks of the industry. Another, more pragmatic view. A The first design is an isolated 42 V power source using a 42 V starter/alternator can serve start/stop mode, recuperation and boost mode as well. The whole power demand of the electric loads that work at 12 V is sourced by a DC-DC converter.The design is realized in the 42 V version of the Toyota Crown. The technical challenge of that design is to control the heat dissipation of the DC-DC converter that typically has a power of 2 kW. That is the reason why Toyota chooses a liquid cooling system for the DC-DC converter. The second technical challenge is the belt, when using driven starter/alternator, due to the high load at the start operation. Cost wise, the highest impacts are made by the belt-driven or integrated starter/alternator, DC-DC converter with cooling system, and the 36 V battery with battery management. The second design is very comparable. The DC-DC converter is a smaller one additional electrical loads at 42 V. The cost savings are practically cancelled by additional cost of the loads now designed to work at 42 V instead at 12 V. The third design requires a change of all electrical Ioads from 12 V to 42 V. The benefit of this solution is that there is no need for a DC-DC converter and for the second (12 V) battery. But we identified extraordinary high additional costs. The highlights are: decentralized DC-DC converters for some 12 V actuators; 42 V design of small motors; countermeasures against short circuits; power supply of ECUs.
Opportunities and challenges of advanced automotive powernets
Möglichkeiten von und Herausforderungen an neue fahrzeugtechnische Energienetze
2003
7 Seiten, 6 Bilder
Conference paper
English
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