EMFIS

EMFIS (Electromagnetic Flux Imaging Scanner) enables highly-effective, rapid and reliable non-intrusive fault finding, performance characterisation and production-line quality assurance. Magnetic field measurements are coupled with post-processing algorithms to conduct NDT scanning of the windings of electric motors, generators and any electromagnetic (EM) assembly. 

Applications in NDT winding also include electrical machine reverse-engineering, magnetic assembly scanning and as an accuracy refinement technique for in-house finite element analysis (FEA) simulations.

EMFIS provides fundamental winding information in a matter of minutes without the need to destroy a unit, and without days of specialist winding engineer time. Shop-floor winding fault identification has also been invaluable, saving considerable cost and time in issue rectification at later stages in the build process.

The key insight that underpins the impact was the unanticipated development of winding pattern and number of turns (N) NDT scanning functionality. At the project outset the intent was to create a magnetic field mapper, for scrutinising magnetic assemblies and the magnetic flux density inside the airgap of an electrical machine. Unexpectedly, an algorithm was developed that can transform data received from the scanner to reveal the full windings of the machine and the N for each EM coil. As far as the project partners are aware EMFIS is the first and only NDT electrical machine (motors and generators) scanner to exist.

The magnetic scanner functionality was initially targeted to impact shop-floor magnetic quality control and also to refine and increase the accuracy of in-house models and simulation data. Modern electrical machines are designed using FEA simulations to ascertain the real-world performance of the machine in terms of torque, speed, efficiency, power draw etc.

Prior to the development of EMFIS, only macroscopic outputs of an electrical machine could be measured in-house. EMFIS enables visibility and quantification of the magnetic characteristics of an electrical machine, providing insight into its most fundamental characteristics (such as airgap flux density, leakage flux, end winding leakage). Measured values from these fundamental magnetic parameters are now fed back into FEA simulations to calibrate and increase the accuracy of subsequent designs.

The in-house impact of the unexpected development of NDT scanner functionality has been more notable. A large number of electrical machines are wound per year within the business. Statistically a number of these are wound incorrectly, with the wrong winding pattern, or an incorrect number of turns. Macroscopic tests can identify a fault at a later point in the build process, but it cannot identify specifically where or what the fault is. Identifying and locating faults rapidly and more efficiently represents a substantial technological improvement to the existing approach.

Further impact has been made on reverse-engineering services. The business is regularly approached to reverse-engineer legacy aerospace machines for which drawings are partial or no longer exist. A more traditional approach to ascertaining windings requires destruction of a unit and up to a week of time from a specialist winding engineer. EMFIS allows precisely the same information to be acquired in minutes, with no damage to the unit.

The work that enabled development of the NDT algorithms involved FEA simulation of the signals anticipated through the Hall sensor during the scan process. Analysis of large amounts of simulated data enabled the identification and successful development of the technique. It is highly unlikely that the technique would have been developed using real-life scan data.

The EMFIS scanner is currently a proof-of-concept technology. It is benefiting the consortium (NEMA LTD and Deva Technologies LTD) and their aerospace customers as a shopfloor inspection, reverse-engineering and quality control tool. Wider exploitation would require a redesign and additional development before the system can be marketed as a commercial product.

The EMFIS system has been used for reverse-engineering of legacy aerospace electrical machines since its development. In each instance it has delivered time and cost efficiencies for the customer. EMFIS has also been used for dielectric strength testing of bespoke commutators and for characterisation of existing devices.

The technology has benefited aerospace customers through reduced cost and lead times.

The long-term intent is to redesign the system using learnings from shop-floor usage to create an improved scanner concept for commercial exploitation in universities, motor manufacturers, test houses and motor rewind businesses.

EMFIS was developed during the COVID-19 pandemic and therefore ability to disseminate the technology at conferences and exhibitions was impacted. Since 2022 NEMA has disseminated the technology at a number of UK Magnetic Society (UKMS) conferences. Subsequently, interest has been shown by a number of aerospace companies.