The need to meet legislative requirements combined with a consumer desire for power and driveability is fuelling growth in the high performance hybrid electric vehicle (HEV) segment. The design of these vehicles is proving challenging, and experts at Eaton Bussmann believe that component standards must be implemented if OEMs are to keep costs down.
Existing standards
Eaton Bussmann is the electrical division of Eaton, specialising in the development and manufacturing of circuit protection, power management and electrical safety technologies. One of its main business units produces fuses that are used in a wide variety of industries, including automotive.
According to Peter Amrein, Senior Field Applications Engineer, Eaton, the standards that govern fuse use in electrified vehicles are causing issues. “A quick glance at standards available today makes it clear that, alongside general standards and manufacturer-specific standards, there are also additional customer-specific requirements,” he explained during an Automotive Megatrends webinar. “This means it is difficult to deduce design cycles and qualification processes.”
There are two general standards applied when it comes to introducing fuses in vehicles, he said. These are ISO 8820 and JASO D622. Manufacturing standards, like the LV124 that was drawn up by the Volkswagen Group, provide more specific requirements for OEMs.
The issue with manufacturing-specific standards is that the testing parameters, particularly within current drive cycle tests, “are not very onerous from a fuse perspective,” Amrein remarked. “They also do not reflect real-life EV applications.” The general standards, he continued, “are not fully applicable to high speed aR fuses, which are now generally chosen for the purpose of battery protection.”
Component vs system
As well as suggesting that the existing standards are insufficient, Amrein thinks that they should differentiate between using fuses on a component-only basis, and using them as part of a system.
“When we are selecting and qualifying the fuses for automotive applications, there is a requirement for the fuses to adhere to the specifications as an individual, i.e. on a component level, as well as a component interacting with other devices, on a system level,” he explained.
This can pose a number of unique challenges for automotive fuse manufacturers, admitted Amrein. For example, “load profiles are more vigorous and random… because the accelerating and stopping procedures are not well defined in cars.”
Sam Mudge, Product Manager, Eaton, echoed this statement, suggesting that a vast amount of R&D and future investment for fuses will be focused on the challenge of system integration. This is particularly prominent for high performance HEVs, as “all projects with higher voltages and higher currents pose problems because they do not have any standards.” The standards described above are targeted at vehicles running at less than 500-volts dc. “OEMs are striving to make HEVs that have more power, a greater range and can be charged more quickly. That all requires higher voltages, and these do not have any standards for fuse qualification.”
Two levels
“One of the main challenges for HEVs at the moment is that the field is ever-changing,” explained Mudge. “No two applications are the same, and we see on-going challenges in terms of increasing power requirements, greater range, and faster cars. Automotive qualification, which is well established in the internal combustion engine (ICE) field, is very different in the world of electrical components.”
The lacking standards are not limited to fuses, but are also having an impact in many other electrical components across the vehicle. “There is a design challenge across the whole system when it comes to electrification. Without commitment to a common global standard, it leaves much up to interpretation for OEMs, suppliers and component manufacturers. Different parties will come to a design with conflicting product specifications. This can add complexity in the design cycle for the OEM or even a Tier 1, which only results in longer testing periods, longer system design time, and additional cost,” he concluded.
