ISSUE 012 Winter 2021 Sigma Powertrain EMAX transmission dossier l In conversation: David Hudson l 48 V systems focus l 2021 Battery Show North America and Cenex-LCV reports l Everrati Porsche 911 digest l Switching insight l Motor laminations focus

Signal sampling with frequencies of up to 1000 kHz makes it possible to display and analyse even very short current peaks in detail. The gateway then converts signals into the standard XCP-on-Ethernet protocol, which allows the acquisition of measurement signals via standard data acquisition tools to integrate the system into a developer’s existing tool chain. As time stamps are assigned to the data, it is possible to establish time relations to other previously recorded measured quantities, for example CAN signals from various ECUs. Other components The inverter is the main focus for components supporting 48 V designs, but there is also demand for 48 V in compressors and heaters, water pumps and other subsystems using 48 V. This puts more pressure on the design of passive components such as capacitors, where the main engineering challenges are the filter for EMI and the DC-link capacitor. One approach is to use a hybrid capacitor that has a wet electrolyte and a polymer electrolyte to get the reliability needed for automotive designs at 48 V with smaller size and higher current capability than 12 V devices. The design of the capacitor depends on the combination of the electrolyte and the polymer. If the area is not well-distributed, localised self- heating occurs and the electrolyte will deteriorate, shortening the lifetime of the device. For the DC-link capacitors in an 11 kW 48 V inverter, for example, using a hybrid capacitor can reduce the space required by 40% by replacing five electrolytic capacitors with three hybrid devices measuring 18 x 35 mm. Alternatively, five hybrid devices in the same space can handle 45% more current, allowing a power of 16 kW. This higher power is being requested for P4 hybrid designs. The EMI filter has a different set of requirements with the higher currents at 48 V, meaning traditional differential choke filters cannot be used. Here, a ferrite core material sits directly on the busbar in differential or bus mode. The dual-mode choke with a magnetic node between the busbars increases the differential mode between the bus bars to 250- 300 A. The EMC filter between the main PCB and the DC supply can use a choke that can work as a filter in both common and differential modes in a single part. The ferrite outer ring of the choke is used as the common mode path, and the tongue is combined with an air gap and the outer ring as a defined differential mode path. This provides for low DC losses owing to the busbar’s low current density, while the differential mode can be influenced by the core design with the flux remaining mostly in the ferrite core. Ferrite materials with an attenuation of 5000 mu can operate at up to 150 C and 1 MHz to prevent any EMI noise in the AM band. For 48 to 12 V DC-DC converters, tantalum and polymer capacitors are used to filter the output of the converter, the main difference being the lifetime and mechanical aspects of the equivalent series inductance and resistance (ESL and ESR). One important point is to take a modular approach to design. Designers are using pre-assembled capacitor arrays in parallel with the busbars to go directly on the AC side, so they don’t need to worry about soldering issues, which can cause failures. This allows a low ESL based on the busbar topology by compensating for the inductance of the positive and negative busbar by putting them close together. 48 V power distribution Adding a 48 V battery to power a heavier powertrain and chassis-system loads provides options to engineers. Now there is a choice of adding systems that can deal directly with a 48 V input, or to retain legacy 12 V electromechanical loads such as pumps, fans and motors and instead convert the 48 V to 12 V via a regulated DC-DC converter. Mild hybrid power delivery systems are slowly adding 48 V loads but still use a large centralised multi-kW 48-12 V converter that feeds 12 V around the vehicle to the 12 V loads. However, this centralised architecture does not take full advantage of a 48 V power distribution network and cannot take advantage of improvements in DC-DC converter topologies, control systems and packaging. The vast majority of these centralised DC-DC converters are bulky and heavy, since they use older, low-frequency Testing 48 V systems can be challenging and requires careful placement of the current sensor (Courtesy of CSM) Winter 2021 | E-Mobility Engineering 39 Focus | 48 V systems