Abstract
For the following reasons, the 42V network will be introduced onto the market: the electrical power increase required in the vehicle, new consumers on the car network, but its cost might constitute an obstacle to its introduction. In this paper VALEO ELECTRICAL SYSTEMS proposes a concept of 42V alternator by switching two stator windings either in parallel or in series, depending on the rotation speed of the machine.
The original concept enables high power and high efficiency. In parallel mode , at high speed ,we obtain an optimized power of 6 kW and a 20% increase in alternator efficiency (max 80%). This is obtained by a small number of stator turns i.e. a small stator resistance. The concept is shown in a 42V configuration. The main work and innovation is dealing with the electronics. All power electronics are implemented on the rear of the alternator. Switching between the two modes has been studied in order to avoid high frequency, over-voltage and current ripple. The strategy used enables a smooth switch which is not damaging for the electrical network.
42V network will be led by electrical power increase, the series-parallel will be a good solution. Moreover, the need for control of green house emission gas in the world could require new electrical functions : C02 emissions were 186g/100km in 1995.They must be reduced to 140g/100km in 2008. A combined alternator/starter /boost machine using more electronics, belt-driven or integrated in the engine, could meet these requirements but at a higher cost.