Demagnetization Analysis for Halbach Array Configurations in Electrical Machines

Abstract

-This paper proposes and investigates an analytical method for assessing the risk of potential, irreversible demagnetisation in the PMs of electrical machines, equipped with n-stages, Halbach arrays. The higher risk of demagnetisation, synonymous with Halbach arrays imposes that the method be both load and temperature dependant. In fact, the proposed method studies the magnetic field distribution in the air-gap and PM region, for various operating temperatures and expresses these fields as analytical expressions for the no-load and peak load conditions. The model can cater for Halbach arrays with up to n stages, thus making it a versatile tool that can be utilised for various Halbach configurations. Finite element analysis is used to validate the method.The analytical tool is then used for the design and analysis of a high torque density, outer rotor, traction motor. The motor is for an aerospace application and its operating duty cycle imposes very high, short time, peak load conditions at elevated temperatures, posing an elevated risk of irreversible, PM demagnetisation. The model is used to investigate various Halbach configurations for this application, in order to reduce the demagnetisation risk and also improve the general performance of the machine. The analytical method thus provides a computationally efficient tool that can be used to predict and prevent demagnetisation in Halbach-equipped, electrical machines operating in harsh environments such as the aerospace sector.

Design optimization of Halbach array permanent magnet motor to achieve sensorless performance using genetic algorithm

“…It is seen that they are higher in Halbach than SMPM machines. The temperature effects were investigated on performance of Hallbach Machine in (Galea, et al, 2015). In the current study, this impact can be seen from the results for 50 o C and 80 o C at x2 loading given in Table VIII.…”

Design and optimization of a high power density machine for flooded industrial pump

“…12. One of the main challenges with PM machine is the requirement to ensure that no partial or full demagnetization occurs for all operating conditions [15]. Thus a demagnetization prediction analysis is performed using finite element simulation.…”

Trade-off analysis and design of a high power density PM machine for flooded industrial pump

“…This arrangement led to improve the air gap flux density with a more sinusoidal waveform which results in a more sinusoidal back-EMF, a lower torque ripple and lower iron losses, resulting in a higher torque [2,12]. Also, with Halbach arrays, other aspects of the machine, such as the rotor yoke can be significantly reduced [13]. The drawbacks related to this arrangement are the higher cost and complexity of manufacturing [2].…”