Eco Innovation Application Summary ZFThis page was last updated on 16th March 2022
Title of the Innovative Technology: 48V Integrated Starter Generator (ISG) with efficient alternator function for use in hybrid powered passenger cars (M1) and light commercial vehicles (N1).
ZF Friedrichshafen AG, Graf-von-Soden-Platz 1, 88046 Friedrichshafen, GERMANY
The innovative technology is a 48V Motor-Generator (MG) – located on the input shaft of the transmission and fully integrated in its housing – plus a 48V/12V-DC/DC converter. Based on the system layout, the 48V MG is also referred to as an Integrated Starter Generator (ISG). Since the main on-board power supply voltage remains at 12V, the system is technically the same as a 12V MG. Focusing only on the generation of electricity the system operates like a 12V alternator.
The 48V ISG converts in alternator mode mechanical in electrical energy. With the MG directly connected to the transmission input shaft no mechanical losses occur between the drive source and the ISG. Thus, the total alternator efficiency is enhanced in comparison to a belt-driven system layout (BSG). A rectifier is needed because the electrical energy is created as alternating current and the on-board network and the battery need direct current. The rectifier uses MOSFET-technology (metal oxide semiconductors field effect transistors) and is also fully integrated in the transmission housing, keeping the lossy wiring as short as possible. Like other already approved high efficiency alternators and 12V MG the MOSFET-technology improves the efficiency by reducing the rectifying losses. In addition, the higher voltage level of 48V leads to a lower current for the same power, reducing the power losses in the rectifier furthermore. In respect to the 12V vehicle on-board network a 48V/12V-DC/DC converter is mandatory. However, the power losses of the DC/DC converter compensate some of the gained efficiency improvements by ISG and rectifier technology. But the overall system still shows a noticeable efficiency improvement in comparison to a regular 12V alternator.
The present application is focusing on the alternator function. A belt-driven 48V-system has already been validated as Eco-Innovation based on NEDC: Commission Implementing Decision (EU) 2019/314 (based on NEDC) and as generic decision in (EU) 2020/1102. With Commission Implementing Decision (EU) 2020/1167 a 48V-based system as generic decision under WLTC conditions has been approved by the Commission in August 2020. Rectification with MOSFET-technology has already been validated as Eco-Innovation: Commission Implementing Decision (EU) 2017/785 (generic decision), 2015/158 (Bosch/SEG) and 2016/588 (generic decision).
The hereby submitted application has already been approved in the EU by the European Commission in Commission Implementing Decision (EU) 2022/252, amending Commission Implementing Decision (EU) 2020/1167, and was given the Eco-Innovation code “32”.
The simplified calculation methodology uses input data from component testing and calculates the off-cycle CO2 savings. The reduction potential is approximately 1.5 g CO2/km.
In the reference year 2017 there were sold less than 1000 vehicles worldwide with a 48V ISG plus 48V/12V-DC/DC converter. In this case the market penetration of 48V ISG in the EU market does not exceed 3%. Frist approved 48V-alternator Eco-Innovation is the belt-driven system for hybrid powered M1 cars in Implementing Decision (EU) 2019/314.
The 48V ISG plus 48V/12V-DC/DC converter replaces the conventional 12V alternator. Alternators are essential for the on-board production of electric energy and, therefore, are essential for the safe operation of the vehicle.
As foundation the testing methodology “Method 1” described in Commission Implementing Decision (EU) 2019/314 for 48V motor-generators plus 48V/12V-DC/DC converter is used (refereeing to ISO 8854:2012). But one important difference exists:
Based on ISO 8854:2012 the belt-driven system in (EU) 2019/314 uses the same operating points ranging up to 10 000 min-1. However, the ZF system is located directly on the transmission input shaft and therefore the rotational frequencies of the ISG are lower. In that respect the operating point rotational frequencies are adjusted. The new proposed operating points for an ISG system are based on the engine speed operational area during the WLTC type approval procedure.
Since the 48V ISG and the DC/DC converter are not provided by the same supplier, both components are measured standalone and the results are combined as proposed in CID (EU) 2019/314 “Method 1”.