The research and optimisation of efficient, low cost, ultra high speed PM machines

Abstract

Manufacturers of electric motors for industrial products are often able to lead the market by placing a focus on high speed, compact, low weight and low cost designs which maintain a high motor efficiency. The current generation of battery powered electric drives for domestic products consists of a power-dense high-speed permanent magnet brushless DC motor which is controlled by a high efficiency digital drive to spin the rotor at over 100,000rpm. The purpose of this project is to pursue a new type of mains powered high-speed (150,000rpm) highly efficient (>85%) motor, from development of fundamental theory and modelling to a carefully designed prototype, matched to a given requirement, and practically validated as a fully built prototype tested in excess of the designed speed. The targeted motor input power is 750W. A thorough literature review is conducted to view all possible motor types. A permanent magnet brushless DC motor is preferred due to its advantages of high power density, compact size and reliable high speed operation. A hybrid simulation approach which combines the advantages of both analytical simulation and finite element simulation is utilised. Precise loss estimation is investigated to support the creation of an analytical simulation model. The accuracy of the constructed analytical simulation model is validated by 3-dimensional finite element modelling. This project puts particular focus on motor per unit material cost with design for mass production in mind. The elimination of high performance but costly motor raw materials, such as high residual flux density rare-earth permanent magnets, low loss density amorphous steels and stranded wires, while still keeping the same level of motor performance in ultra-high speed applications, becomes the biggest challenge in this project.