Abstract

There are three principal sources of noise and vibration in electrical machines: electromagnetic sources, mechanical sources, and aerodynamic sources. Nowadays, one of the major advantages of permanent-magnet synchronous machines is their torque density. This density is achieved through a high magnetic flux density in the air gap, which is achieved through hard magnets. Unfortunately, in these machines, electromagnetic forces have been identified as the main source of vibration and noise, and high magnetic flux densities make these vibrations and noises more significant. With the aim of better understanding the relationship between electromagnetic forces and design variables, this article, which is the continuation of previous work, firstly describes a study of the sources of magnetic forces in permanent-magnet synchronous machines. Subsequently, an analytical model for the computation of the radial forces originating from electromagnetic sources in permanent-magnet synchronous machines is stated. This model analyzes the forces on both the rotor surface and the base of the stator tooth. The analytical results were corroborated through simulations using the finite element method (FEM) and also by experimental tests performed over two prototypes. The results achieved by the analytical model show good agreement with both FEM results and experimental measurements.

Highlights

  • Today, electrical machines are considered a mature technology

  • permanent-magnet synchronous machines (PMSMs) can be created by three different sources: magnetic pressures originating on the stator, magnetic pressures originating on the rotor, and forces created by eccentricities

  • The magnitudes of the harmonics could not be validated with the obtained experithis article, an analytical model based on spatial

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Summary

Introduction

Electrical machines are considered a mature technology. A good indicator is that in developed cities, more than 65% of the electrical consumption is due to electrical machines [1]. It is well known that the performance of electrical machines, for instance magnetic order to obtain accurate results, it is essential to properly define the spatial distribution forces or torque ripple, on the flux density in the air gap. In order to improve accuracy, searchers employ thisused method becauseapproximations the distributionfor is not exactly rectangular and[16] This or some authors have trapezoidal direct current (DC) motors assumption may lead to significant errors [15]. There have been different studies about magnetic forces in which the calculi were based on application of the law of Maxwell’s stress tensor and the use of the Fourier series [26–28]. We were unable to find a simple model where the analytical expressions were related to design parameters In these models, the traceability of the problematic harmonics in the magnetic forces that need to be eliminated or reduced becomes a problem.

Sources of Magnetic Forces in PMSMs
Magnetic Pressures on the Stator
Oscillating Magnetic Pressure Due to the Stator Slots
Oscillating Magnetic Pressure Created by the Stator Winding
Magnetic Forces Due to Eccentricities
Analytical Model
Complex Fourier Series
Magnetic Flux Density Created by Magnets in a Slotless Machine
Magnetic Fluxto
Magnetic Flux Density Created by Coils in a Slotless
Effect of the Stator Slots
Computation of the Magnetic Forces on the Stator
Validation
Analytical
Surfaces
Magnetic
11. Spectrum
13. Magnetic pressure distribution coils on the rotor surface of the Qs36p15
17. Magnetic
21. Harmonics
22. Forces
Conclusions
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