Technology Development: New press-fit carbon sleeve enables affordable spin speeds up to 30,000 RPM
Increasing the spin speed of the electric machine is widely believed to be one of the most attractive ways to improve power density to increase efficiency and, therefore, the range of electric vehicles without increasing the size, cost, and mass of the battery pack. The challenge is developing high-speed machines that meet automotive durability requirements and can be manufactured in high volumes at a commercially attractive price.
As part of an Innovate UK project funded by the Office for Low Emission Vehicles (OLEV), Drive System Design (DSD) and the National Composites Centre have recently developed a solution to this challenge by developing a composite rotor sleeve to replace the traditional magnetic bridge. As well as optimising the design and validating the resulting efficiency improvements, the programme has developed a scalable design for high volume manufacture.
For a machine operating at up to 30,000 RPM, DSD’s analysis shows a potential power density increase of up to 37% compared with a typical machine, together with significant savings in magnetic materials. Substantial efficiency improvements were also demonstrated for motors running at lower speeds. In addition, DSD has developed complementary technologies for ultra-high-speed, very high precision control, high-speed single and multi-speed transmissions, optimisation of system architecture choices, and the test and validation of high-speed machines in separate programmes.