Eccentricity Effects on NVH Performance of Interior Permanent Magnets Machines for Hybrid and Electric Vehicles

For the hybrid electric vehicles (HEVs) and electric vehicles (EVs) applications, the electric machine drive unit system provides the main noise source, especially in the presence of faults. Eccentricity is one of the most common faults, which is mainly caused by the motors' package design and assembling process. There are four main types of eccentricity for motors: static offset, dynamic offset, static tilt and dynamic tilt, which are presented and analyzed. Both two-dimensional (2D) and 3-dimentional (3D) finite element analysis (FEA) are utilized in the electromagnetic field analysis for an Interior Permanent Magnet (IPM) motor. The corresponding methodologies for the mesh and force mapping to the mechanical FEA for the NVH analysis are presented. The NVH test shows that both 2D and 3D FEA can provide reasonable accuracy for the motor eccentricity fault analysis. The 2D FEA is the most common method used in the design optimization and early performance prediction for electrical. For the 3D FEA, due to the high requirement for the computer hardware and computation capability, it is usually used in the final validation for electrical machines' performance. The sensitivity of motor performance versus the airgap heights and eccentricities are studied.

A Novel High Performance Discrete Flux Integrator for Control Algorithms of Fast Rotating AC Machines

This paper deals with the digital implementation of a motor control algorithm based on a unified machine model, thus usable with every traditional electric machine type (induction, brushless with interior permanent magnets, surface permanent magnets or pure reluctance). Starting from the machine equations in matrix form in continuous time, the paper exposes their discrete time transformation, suitable for digital implementation. Since the solution of these equations requires integration, the virtual division of the calculation time in sub-intervals is proposed to make the calculations more accurate. Optimization of this solver enables faster runs and higher precision especially when high rotating speed requires fast calculation time. The proposed solver is presented at different implementation levels, and its speed and accuracy performance are compared with standard solvers.

Modal Analysis and Rotor-Dynamics of an Interior Permanent Magnet Synchronous Motor: An Experimental and Theoretical Study

This paper investigates mechanical vibrations of an interior permanent magnet (IPM) synchronous electrical motor designed for a wide range of speeds by virtue of the modal and rotordynamic theory. Mechanical vibrations of the case study IPM motor components were detected and analyzed via numerical, analytical and experimental investigation. First, a finite element-based model of the stator assembly including windings was set up and validated with experimental and analytical results. Second, the influence of the presence of the motor housing on the natural frequencies of the stator and windings was investigated by virtue of numerical modal analysis. The experimental and numerical modal analyses were further carried out on the IPM rotor configuration. The results show that the natural frequencies of the IPM rotor increase due to the presence of the magnets. Finally, detailed numerical rotordynamic analysis was performed in order to investigate the most critical speeds of the IPM rotor with bearings. Based on the obtained results, the key parameters related to mechanical vibrations response phenomena, which are important when designing electrical motors with interior permanent magnets, are provided. The main findings reported here can be used for experimental and theoretical mechanical vibration analysis of other types of rotating electrical machines.

Limitations and Constraints of Eddy-Current Loss Models for IPM Motors with Fractional-Slot Concentrated Windings

This paper analyzes and compares models for predicting average magnet losses in interior permanent-magnet motors with fractional-slot concentrated windings due to harmonics in the armature reaction (assuming sinusoidal phase currents). Particularly, loss models adopting different formulations and solutions to the Helmholtz equation to solve for the eddy currents are compared to a simpler model relying on an assumed eddy-current distribution. Boundaries in terms of magnet dimensions and angular frequency are identified (numerically and using an identified approximate analytical expression) to aid the machine designer whether the more simple loss model is applicable or not. The assumption of a uniform flux-density variation (used in the loss models) is also investigated for the case of V-shaped and straight interior permanent magnets. Finally, predicted volumetric loss densities are exemplified for combinations of slot and pole numbers common in automotive applications.