Electric Motors and Drives (EMD)

The present state of the art is to use advanced torque estimation techniques based on electrical current and rotational speed measurements. Accurate torque measurement is desirable but has not been possible using competing torque measurement systems. Using Transense SAW sensors eliminates the need for estimation and gives reliable torque and temperature measurement from the motor rotor that can be used to improve both motor efficiency and safety, and is suitable for the growing EV motor market. See SAW in Electric Motors for vehicles for more information.

EMD also has links to other sectors with increasing electrification in aerospace and industrial machinery.

High-quality e-bikes utilise torque sensors to provide responsive performance, a natural feel, and a safe ride. Transense Surface Acoustic Wave (SAW) technology offers an exciting alternative to revolutionise e-bike drive systems. SAW sensors are compact, lightweight, highly accurate, remarkably reliable (immune to vibration, moisture, and electromagnetic interference), and cost-effective. This unique technology with its ability to be seamlessly integrated into the e-bike drive system can significantly reduce the size, weight, and cost of the drive system, delivering an exceptional e-bike experience.

A key constraint in high-performance electric motors is the temperature of the rotor, due to the impact of heat on the magnetic field strength. Permanent magnet motors utilise magnets that contain rare-earth materials to increase the operating temperature range of the magnets and maximise the power density of the motor. Even electric motors which do not use permanent magnets, such as induction, switched reluctance, and externally excited machines, are sensitive to rotor temperature. Adding in rotor temperature measurement can allow rare-earth material content to be reduced or eliminated by enabling the move to alternative magnet compositions or magnet-free motor technologies. Having a live measurement of the rotor temperature allows more performance to be extracted from the motor by reducing or eliminating the safety factors required where there is no actual measurement. Tests have shown that thermal models for rotor temperature are not reliable when compared to actual measured results, and under real-world driving conditions, having temperature measurement can allow more performance to be extracted from a given motor.