This article originally appeared as a sidebar to "How Will We Fuel the Future?" from the June 2022 issue of Power Transmission Engineering.
Here’s a small sample of the technologies discussed during the CTI Symposium 2022 in Novi, Mich.
Thermal Management for EVs
Energy is a precious commodity in electric vehicles. Using sophisticated thermal management, designers can extend vehicle range at a stroke by reducing the power needed for optimal temp control of interiors and batteries. High-performance thermal management is also a must for fast charging – and the performance, operational reliability and service life of various system components all depend on a functional thermal management setup. At CTI, topics in the field of thermal management included thermal analysis tools for EDUs, a central coolant control module, and highly effective immersive cooling.
When checking EDU subsystems and components for smooth operation or dangerous hot spots, today’s designers have various tools at their disposal. But as Michael Furness, Drive System Design, USA, explained, “With this kind of silo-based design approach, you risk overlooking crucial thermal interactions at the system level.”
The Thermal Analysis Tool developed at Drive System Design accesses existing subsystem datasets to quickly generate a system-level thermal model of the design. The tool has been automated to ensure fast modeling. It can be used cost-effectively at every stage of the EDU development cycle and can help to inform design decisions on every level.
By running a system-level thermal analysis early on, designers can reduce the likelihood of costly changes further downstream. The short simulation cycle significantly reduces development time and supports designers without the need to parameterize and apply costly FEA programs. Thanks to the tool’s modular implementation of heat transfer physics, designers can use simple empirical equations at an early design phase to obtain a rough understanding quickly. When more mature analyses become available, they can be fed into the tool to improve accuracy.
Small Electric Motor Improvements
As all designers of electric motors know, seemingly small improvements can yield tangible benefits. In his presentation, DeeDee Smith (Solvay Materials, USA) discussed optimizing the insulation materials used in electric motors.
Specifically, the issue concerns the slot liners that shield the stator core from the winding. As OEMs progressively migrate from 400-volt systems to 800 volts or higher, it’s becoming clear that traditional paper/paper laminate insulation is no longer ideal. To address that issue, Solvay has been working with e-motor designers to evaluate the suitability of Ajedium PEEK slot liners as a new high-voltage, high-temperature solution. As their findings show, Ajedium PEEK slot liners are an advanced alternative that combines excellent electrical and mechanical performance with greatly reduced thickness. In some cases, volumes can be reduced by up to one third, compared to established solutions.
Engineers can exploit this advantage to increase the motor’s power density, either by making the e-motor more compact or by using the free space in a way that enhances performance. The thermoplastic PEEK film is temp-resistant to 240°C and offers improved thermal conductivity — more than three times that of current paper and paper laminate materials. This in turn helps to reduce overall motor temperature.
High-Speed Traction Motor Production
How do you produce rotor and stator cores for traction motors at high speeds and volumes, at low costs and in perfect quality? In his presentation, Max Thieme (Schuler Pressen, Germany) examined the optimal solution for this challenging task.
First, the speaker presented and compare the basic methods for stamping sheet metal for electric motors. He focused on ultra-modern bonding techniques such as interlocking, gluing and bonding varnish/Backlack, all of which can be used to combine metal sheets into a complete package. Bonding varnish in particular offers convincing benefits. Unlike interlocking and welding, this process rules out short circuits between individual sheets. As a full-area bonding method, it also outperforms gluing – no liquid can penetrate, and thermal conductivity and NVH behavior are both better.
Finally, Thieme explained why progressive dies are suitable to produce traction motor stacks in typical quantities and sizes. This method kills two birds with one stone: high speed stamping, and high-quality bonding. To eliminate the downside of handling separate sheets, a fully automated system collects sheets below the progressive die and brings them to the gluing stations in a controlled and secure manner. These gluing stations are freestanding units that offer full control over all process parameters such as pressure, temperature and time. The solution is usually offered as a turnkey system that covers everything from winding off the raw material to the finished laminate stacks. That said, retrofits for existing machines are also available.