Fractional-slot Concentrated-winding Interior Permanent Magnet Research Articles

Vibration Optimization of FSCW-IPM Motor Based on Iron-Core Modification for Electric Vehicles

In this paper, to optimize vibration of the fractional slot concentrated winding interior permanent magnet (FSCW-IPM) motor for electric vehicles (EVs) without sacrificing any torque performance, modifications of iron-core structures are proposed. First, the effects of basic stator/rotor auxiliary slots on torque, cogging torque, torque ripple, and 2nd order spatial harmonic of radial force are investigated by finite element analysis (FEA). The combinations of stator/rotor auxiliary slots, which can optimize vibration with maintained torque, are analyzed. To improve torque and optimize vibration, uneven airgap rotor is proposed. With variation of the uneven air-gap rotor, torque improvement and vibration reduction do not contradict each other. The vibration levels of FSCW-IPM motors are calculated by magnetic-mechanical coupling models, while the peak vibrations are optimized with the proposed methods. Inductance, torque, and vibration experiments of the FSCW-IPM motor with the uneven airgap rotor are performed. The theoretical and experimental results both validate effectiveness of the proposed methods for torque improvement and vibration optimization.

Partially-Coupled d–q–0 Components of Magnetically-Isolated FSCW IPM Machines With Open-End-Winding Drives

Fractional-slot concentrated winding interior permanent magnet (FSCW-IPM) machines have been designed with very low winding mutual inductance for magnetic isolation features required for improving their fault-tolerant capabilities. These magnetically-isolated FSCW-IPM machines no longer adhere to the preconditions required for a conventional abc-to-dq0 transformation. As a result, it is found in this article that d-, q-axes could couple with 0-axis in magnetically-isolated FSCW-IPM machines. Considering the second-order reluctance component, this phenomenon leads to third-harmonic injection in phase voltages during normal operation, which can be cancelled out in terms of line-to-line voltage for Y-connected three-phase system. However, for open-end-winding machine drives without winding neutral point constraint, these voltage harmonics will show up in the winding voltage waveforms. Study shows that the amplitudes of these extra harmonics are determined by both saliency ratio and zero-axis current. The bandwidth of the proportional integral (PI) current regulator as well as switching frequency should be carefully determined to be able to take into account the major harmonics injected in phase voltages. Experimental verification on a 12-slot/10-pole prototype machine with spoke PMs has been carried out to show the impact of this phenomenon.

A Nonlinear $q$-Axis Inductance Modeling of a 12-Slot 10-Pole IPM Using Approximate Analytical Methods

This article introduces a novel nonlinear model for the $q$ -axis inductance of a Fractional Slot Concentrated Winding Interior Permanent Magnet (FSCW-IPM) machine in order to decrease the time needed to obtain a solution. The complicated geometry and nonlinear magnetic behavior of the core make analytical modeling difficult. So numerical methods are usually used to model machines in which magnetic saturation plays an important role. The winding function of a 12-slot 10-pole FSCW-IPM machine is analyzed and a magnetic equivalent circuit is obtained using the Lumped Parameter Method (LPM) according to the MMF distribution analysis. A mathematical function which represents the magnetic behavior of the core material is appropritely selected to reduce the equations, which show the relationship between the flux and MMF of every lumped parameter into the one equivalent equation. After that, perturbation theory and Pade approximants are used to solve the nonlinear equivalent equation. Finally, a new nonlinear analytical model and solution method is introduced for 12-slots 10-pole FSCW-IPM and the simulation time is decreased to under 0.5 s while it takes about 10 mins with FEA because the proposed method does not need any iteration. The proposed method is compared with FEA and experimental results and the comparison shows the proposed method has sufficient accuracy.

Design and Performance Comparison of Fractional Slot Concentrated Winding Spoke Type Synchronous Motors With Different Slot-Pole Combinations

Fractional slot concentrated winding (FSCW) interior permanent magnet (IPM) synchronous motors are nowadays an attractive solution in automotive applications due to their advantages in terms of high performance and manufacturing simplicity. Among the different topologies, the spoke type is an effective configuration when high torque density is required. On the other hand, the motor performance are heavily related to the selected slot-pole combination. This choice is critical in demanding automotive applications, such as electric power steering (EPS) systems, where high constraints in terms of torque density, torque quality, flux weakening performance, and noise/vibration/harshness are requested. This paper deals with the design and analysis of eight optimal slot/pole combinations FSCW IPM spoke type EPS motors. Two different low cost heavy rare earths free PM typologies, ferrite and hot-pressed NdFeB, are considered. A design and optimization procedure based upon the finite element analysis is presented. The impact of the magnetic properties and the slot/pole combination on the optimal motor dimensions, torque density, and motor cost is discussed. Cogging torque, torque ripple, electromechanical performance, and the stator deformation of the machines are evaluated, and the results are compared, highlighting the advantages and the differences among the solutions.

Design and Comparison of Three-Phase and Five-Phase FTFSCW-IPM Motor Open-End Winding Drive Systems for Electric Vehicles Applications

This paper proposes and compares two new fault-tolerant fractional-slot concentrated-winding interior permanent magnet (FTFSCW-IPM) motor open-end winding (OW) drive systems for electric vehicles. The proposed FTFSCW-IPM motors possess the merits of high efficiency, high power density, and strong fault-tolerant capacity. Also, to further improve the reliability of control system, an OW dual inverter drive system is adopted. Furthermore, to better and clearer illustrate the advantages and disadvantages of multiphase machine system, the comprehensive comparison of three-phase and five-phase FTFSCW-IPM motor OW drive systems is carried out from the perspective of motor design and control system. The topologies and the features of the proposed two FTFSCW-IPM motors are analyzed, and the static characteristics are investigated and compared by using the finite-element analysis (FEA). Then, the evaluation of their OW drive system performance is conducted and compared by the simulation based on the MATLAB/Simulink. Finally, the FEA and simulation results are validated by experiment on both prototypes.