In planning its all-new European test facility dedicated to electrified vehicles, Intertek Transportation Technologies started with a consideration even more important than the latest dynamometers and thermal chambers. “Instead of starting by drawing up a list of test machines, we began by questioning our customers about the information they need to make better design and technology decisions,” said David Meek, the company’s U.K. director.
Those key engineering questions included: How will new powertrain electrification technologies perform as they age? What are the most cost-effective strategies for optimizing each system without compromising durability? What are the NVH implications of very high-speed motors? What is needed to support accelerated EV production to fulfill government and industry requirements?
A global supplier of specialist test services with over 1,000 locations worldwide, Intertek’s new European Center of Excellence is scheduled to open in 2021 in Milton Keynes, 50 miles (80 km) north-west of London, England. Capabilities will range from investigating the durability of batteries and electric motors to studying new areas of technology, including electromagnetic interactions at very high motor speeds, with the goal of keeping ahead of the EV development curve.
In Meek’s view, most electric driveline test systems have been developed in response to immediate product development requirements, with too little investment in supporting R&D and strategic technologies. Intertek’s back-to-basics questioning of OEMs and suppliers, in planning the new facility, generated clear directional themes. Firstly, future generations of powertrain must be designed as an optimized single system, rather than a combination of optimized systems. “It means that test systems must be capable of providing data that will illuminate a technology’s interactions across the driveline and even the wider vehicle,” Meek said.
Generating reliable data
There is also the need to generate more detailed data. Further systems integration required a new generation of digital design tools to support design decisions. However, these could only be trusted if they are built around robust data that ensure excellent correlation with real-world performance. To achieve that, test systems need to be designed to capture a wider range of high-fidelity data ensuring an accurate representation of real-world usage – not of historic in-house test procedures.
Meek used the traction motor an example. “Increasing motor efficiency requires optimization of materials, construction techniques, air gaps, thermal management and EMC [electro-magnetic compatibility] performance, with each parameter affecting the performance of the others,” he told SAE’s Automotive Engineering. “The challenge is compounded by the parallel trends of much higher machine speeds [Intertek is currently testing up to 27,000 rpm] and integration with the transmission and power electronics into an electric drive unit.”
These fundamental parameters underline the value of collecting data to support further design refinement. E-motor test systems, for example, could include measurement of NVH while adding high-fidelity power-analysis measurements. This allows the characterization of power consumption early in the design phase – valuable when specifying energy management systems.
Focus on new extremes
Constructing a valuable picture of system performance requires the collection and processing of enormous volumes of test data. It has to cover many more channels and accommodate new extremes such as higher motor speeds and EMC interactions, explained Intertek EV test manager, Giulia Olearo.
The new high-speed motors require data collection into the MHz range. The motors and their power electronics create a new set of complex interactions. “For example, switching around 20 KHz can introduce unwanted harmonics in the AC cables up to MHz frequencies, causing a high amplitude gain overlaying the data,” Olearo stated. “There are a number of areas like this that only an engineer experienced in EV systems testing would predict, yet they are increasingly crucial to data integrity.”
The latest EV power electronics enable voltage pulse-widths down to 1 μs, requiring a sample rate higher than 1 MHz. Otherwise, short pulses can be missed, leading to inaccurate power measurements. Greater focus at the component level helps understand the trade-offs, such as in gear design.
“The more helical the gear profile the easier it is to create a silent transmission – but the more energy is wasted in sliding contact,” Meek offered. He stressed that to increase the efficiency of an EV transmission requires a thorough understanding of multiple parameters including temperature and NVH, “across a range of operating conditions never previously seen in an automotive application.”
Intertek’s new facility will also support development of new modeling tools the company regards as essential to future EV design. The Center of Excellence will support the test and development of e-machines (up to 27,000 rpm), power electronics (up to 1,100 V), integrated axle modules and on-board vehicle electrical systems. Flexible test programs will provide insights at component, system, and systems integration levels. Laboratories will include a climatic chamber with all-wheel-drive ViL (vehicle-in-the-loop) capability, along with battery-test labs.
Meek stressed that even the most costly and high-tech test technology will deliver little valuable data if the test cycles are not representative of how vehicles are used in the real world, including the most extreme usage cases. “The differences between how conventional and battery-electric vehicles are driven can be surprisingly significant, requiring a fresh look at drive cycles,” he noted.
His team is working with a specialist group within Intertek to enable the influence of factors such as the availability of maximum torque from zero rpm to be understood. “We are helping engineers develop the simplest, most-elegant solutions – but the route to achieving those aims is complex,” Meek asserted.Continue reading »