Measurement of Magnetic Properties of Materials at Operational Conditions

The development of new measurement systems and techniques at NPL and other National Metrology Institutes (NMIs) is required to enable the extended characterisation of a range of magnetic materials at the operational conditions of use. In pursuit of sustainable and efficient motor drive systems and decarbonisation within the automotive and aerospace sectors, characterisation of these materials requires a robust metrology infrastructure. These magnetic capabilities give machine designers improved data confidence for optimising performance of motors and allow predictions for component and critical system reliability from design to end-of-life to be more accurate.

International standards provide a robust framework for comparison of magnetic properties of materials. There are however limitations within the specifications of these standards, meaning that measurements performed may not be representative of the operational conditions that magnetic materials will be exposed to. This presentation will outline the work that NPL is undertaking in collaboration with other NMIs, universities and industrial partners to build on the foundations of standard measurements to improve metrological understanding of measurements at an extended range of temperature and frequencies. NPL has recently developed measurement systems to characterise the AC loss of electrical steels at frequencies up to the MHz regime, at higher polarisations and at operational temperatures up to 155 °C. NPL is also developing it’s permanent magnet measurement capabilities to measure magnets between -45 °C to 200 °C to meet the requirements of industry.