Abstract
In high speed permanent magnet (HSPM) machines, the computation of magnet eddy current loss is essential as these losses significantly affect the temperature of the permanent magnet (PM) and electromagnetic performance and can result in irreversible demagnetization of the PM. Several techniques have been adopted to minimize the eddy current loss of the PM; however, superior performance has not been achieved yet. In this paper, the design characteristics of the HSPM machine are analyzed. The PM is covered by a titanium sleeve to retain the PM on the rotor and to further reduce the eddy current loss of the magnet. The undesirable harmonics of the airgap flux density are minimized, which reduces the eddy current loss in the solid PM and rotor. Two existing models, with and without auxiliary slots, are examined and compared with the proposed design having a titanium-based retaining sleeve. The analysis reveals that the eddy-current loss, cogging torque, and iron losses of the PM are reduced by 82%, 73%, and 44.7%, respectively, in the proposed model; however, a marginal increase is observed in the average rated torque profile and open circuit flux linkage.
Highlights
High speed permanent magnet (HSPM) machines have become significantly popular in recent times owing to their utilization in various applications, such as automotive and aerospace applications, gas turbines, air blowers, and spindles
Several challenges exist in the manufacturing of HSPM machines as field windings are replaced by PMs
In PM machines, the eddy current loss is produced by asynchronous harmonics; such harmonics are spatial harmonics in a stator magnetomotive force distribution and time harmonics in a stator non-sinusoidal current waveform, which significantly affect the performance of the machine
Summary
High speed permanent magnet (HSPM) machines have become significantly popular in recent times owing to their utilization in various applications, such as automotive and aerospace applications, gas turbines, air blowers, and spindles. Khan et al.: Analysis and Design of Novel HSPM Machine Considering Magnet Eddy Current Loss the rotor losses are caused by a permeance variation of the airgap due to the slotting of the stator. Rotor shape optimization is the best choice to diminish the eddy current loss and cogging torque while increasing the power density and efficiency of the machine; these approaches have a disadvantage of a low winding factor; a high copper loss occurs for the same output torque [16]. Owing to the return path of the eddy currents in the PM, the eddy current loss is a three dimensional (3D) problem that requires a 3D finite element analysis (FEA) for computation; this technique is significantly time consuming These losses can be calculated analytically, which is considerably effective but difficult to implement [21].
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