E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

May/June 2023 | E-Mobility Engineering 65 Focus | Powertrain testing the company explains. For complete vehicles, the company offers climatic test chambers for performance and efficiency development, along with range testing to EU and US standards. The expert says test systems must be able to match the high performance of modern EV powertrains while being durable enough to deliver repeated test campaigns. He says, “Performance and efficiency are important factors for EV powertrains, requiring highly accurate torque measurement and power analysis systems that look at both the DC and AC systems.” A basic test system consists of a high-speed dynamometer or a pair of wheel-speed dynos integrated with a battery simulator, says the variable- speed drives and controls systems provider. The simulator is needed because EV powertrains are normally tested without their batteries. The company makes drive systems for the test stand industry. These differ from those primarily for industrial applications, for example by using output devices such as inverters and converters that provide higher switching frequencies with lower losses, and through the use of multiple processors along with software developed for test stand applications and internal clocks that can be configured to prioritise different parts of the system. Typical systems tend to be more elaborate than the system described above, however. According to engineers from a vehicle test and validation services provider, they include rigs for testing the performance and durability of EDUs consisting of multiple AC dynos in a mix of high-torque and high-speed machines, battery simulators, coolant and oil conditioning systems and power analysers, along with environmental conditioning. The company says it offers a full complement of testing services at the component, subsystem and system levels, including homologation support, and has recently focused its investment on electrified driveline and battery testing capabilities. Battery testing systems generally focus on endurance and performance, and include environmental chambers, battery cyclers as well as coolant conditioning systems, the company’s engineers say. Naturally, both require control and data acquisition systems. “Also, testing systems – for batteries as well as EDUs – tend to have an environmental test focus,” The expert points out that while automotive OEMs have built up a strong knowledge of the integration of powertrains into vehicle bodies, EV powertrains present new challenges because the sizes of the components and the loads they generate are very different. High torque from low rpm requires a different body structure to handle it, and the ability to identify the loads and their proper paths through the body is key, he says. Integrating the battery is also a challenge owing to the size and weight of a modern pack. That has major implications for weight distribution, overall body stiffness and the balance between vehicle performance and comfort, the expert adds. Energy management is also very different, he says, as testing has to assess the efficiency of the flow of DC from the battery, through the inverter and the electric driveline to the wheels, rather than from burning a mixture of fuel and air through an entirely mechanical driveline to the wheels. “This requires newmethods and materials,” he says. Testing essentials EV powertrains are characterised by high-speed, high power-density input machines, with integrated gearbox systems that deliver high wheel torque from zero speed, explains a global engineering consultancy and services provider, which offers EV powertrain systemdesign, development, integration, testing and validation of components as well as complete vehicles. The company can test e-machines on single-axis test rigs, gearbox systems on input-output rigs and electric drive units (EDUs) on 2WD and 4WD powertrain rigs, an expert from Test rigs for EVs and hybrids have to be able to handle all-wheel-drive vehicles and electric motor characteristics such as maximum torque from zero rpm, which requires very accurate measurement (Courtesy of Ricardo)