" near future operate on electricity—air conditioning compressors, water pumps, oil pumps, and thelike. Due to continuously changing engine speed, these components have rather poor efficiencyratings. Electric motors have the capability of optimizing their operation, independent of enginespeed.This change, though, would overload the conventional 12 V car generators and batteries. Ratherthan increasing the current and corresponding cable cross-sections, it makes more sense to make42 V the future standard. One immediate consequence will be a combined starter-generator placeddirectly on the crankshaft.Prototypes of this unit were presented by Mannesmann-SachsAG at the 1999 IAA car exhibition in Frankfurt, Germany.The unit is a three-phase synchronous engine using apermanent excitation. It is integrated into the flywheel of theclutch and can be used as either a starter or a generator.Efficiency is increased significantly in both modes ofPhoto 6. An application-specificoperation. On one hand, the engine is started at a higherNTS-xx sensor features astarter speed, and on the other, the new generator willconductor configured as a copperproduce much more electric power without increasing powerbus bar.demand on the combustion engine. Very effective start/stopsystems can thus be realized: The engine is switched offwhenever the vehicle stops and started again automatically when the driver wants to go on. These28measures should lead to fuel savings of around 30% compared to today‘s vehicles.A prototype of the starter-generator control unit made by Mannesmann-Sachs (see Photo 5),requires the use of three-phase MOSFET alternators. For control and safety reasons, thesealternators need current sensors for at least two of these phases. Mannesmann uses a customer- specific version of Sensitec‘s NTS-xx system, in this case an NTS-xx hybrid without a conductorfor the working current.The conductor in Photo 6 is configured as a 0.8-mm-thick copper bus bar. At the location of theNTS-xx, the bar takes a U-shaped configuration to generate the necessary magnetic field gradient.For this application, the NTS-xx is mounted directly above the bar and electronically calibrated insitu.This arrangement has many advantages. Production is much easier because there is no need tobreak or disconnect the conductor carrying the working current or even feeding it through theNTS-xx itself. Furthermore, because this version of the NTS-xx can be used for practically allmeasurement ranges (e.g., 10 A, 100 A, or 1000 A), provided the busbar is adaptedcorrespondingly, a great reduction in manufacturing cost can be realized.29References1. H. Lemme. 1998. ?Magnetfeld-Sen soren-vielseitige Helfer,? Elektronik, H.3, S.40.2. A. Petersen. 1985. ?Magnetoresistive Sen soren im Kfz,? Elektronik, H.10, S.99–102.3. G. Reiniger. 1986. ?Drehwinkel mes sung mit Magnetfeldsensoren,? Elektronik, H.23, S.129.4. E. Dettmann and V. Loreit. 1997. ?Center Assembly for Measuring Current as a Function ofMagnetic Field Gradients.? U.S. Patent No. 5,621,377.5. J. Rühl and T. Walther. 1993. ?Strom sensor als Mikrosystem,? Elektronik, H.20, S.42.6. W. Göpel et al. 1989. Sensors —A Comprehensive Survey, VCH-Verlag. Weinheim.30 "