Hybrid and electric vehicle technology has seen rapid development in recent years. The motor and the generator are at the heart of the vehicle drive and energy system and often utilize expensive rare-earth permanent magnet (PM) material. This paper reviews and addresses the research work that has been carried out to reduce the amount of rare-earth material that is used while maintaining the high efficiency and performance that rare-earth PM machines offer. These new machines can use either less rare-earth PM material, weaker ferrite magnets, or no magnets; and they need to meet the high performance that the more usual interior PM synchronous motor with sintered neodymium-iron-boron magnets provides. These machines can take the form of PM-assisted synchronous reluctance machines, induction machines, switched reluctance machines, wound rotor synchronous machines (claw pole or biaxially excited), double-saliency machines with ac or dc stator current control, or brushless dc multiple-phase reluctance machines.

Automotive Electric Propulsion Systems With Reduced or No Permanent Magnets: An Overview

With rapid electrification of transportation, it is becoming increasingly important to have a comprehensive understanding of criteria used in motor selection. This paper presents the design and comparative evaluation for an interior permanent magnet synchronous motor (IPMSM) with distributed winding and concentrated winding, induction motor (IM), and switched reluctance motor (SRM) for an electric vehicle (EV) or hybrid electric vehicle (HEV) application. A fast finite element analysis (FEA) modeling approach is addressed for IM design. To account for highly nonlinear motor parameters and achieve high motor efficiency, optimal current trajectories are obtained by extensive mapping for IPMSMs and IM. Optimal turn- on and turn- off angles with current chopping control and angular position control are found for SRM. Additional comparison including noise vibration and harshness (NVH) is also highlighted. Simulation and analytical results show that each motor topology demonstrates its own unique characteristic for EVs/HEVs. Each motor’s highest efficiency region is located at different torque-speed regions for the criteria defined. Stator geometry, pole/slot combination, and control strategy differentiate NVH performance.

Comparative Study of Interior Permanent Magnet, Induction, and Switched Reluctance Motor Drives for EV and HEV Applications

As a kind of traction device, interior permanent-magnet synchronous machines (IPMSMs) are widely used in modern electric vehicles. This paper performs a design and comparative study of IPMSMs with different rotor topologies (spoke-type PMs, tangential-type PMs, U-shape PMs, and V-shape PMs). The research results indicate that the IPMSM with V-shape PMs is more satisfying with comprehensive consideration. Furthermore, the IPMSM with V-shape PMs is investigated in detail. The influences of geometrical parameters (magnetic bridge and angle between the two V-shape PMs under each pole, etc.) on the performances of V-shape motor are evaluated based on finite-element method (FEM). For accurate research, the effects of saturation, cross-magnetization, and the change in PM flux linkage on d - and q -axis inductances are considered. The back-electromotive force (EMF), flux leakage coefficient, average torque, torque ripple, cogging torque, power per unit volume, power factor, and flux-weakening ability are investigated, respectively. The experimental results verify the validity and accuracy of the process presented in this paper.

Research on the Performances and Parameters of Interior PMSM Used for Electric Vehicles

Three different motor drives for electric traction are compared, in terms of output power and efficiency at the same stack dimensions and inverter size. Induction motor (IM), surface-mounted permanent-magnet (PM) (SPM), and interior PM (IPM) synchronous motor drives are investigated, with reference to a common vehicle specification. The IM is penalized by the cage loss, but it is less expensive and inherently safe in case of inverter unwilled turnoff due to natural de-excitation. The SPM motor has a simple construction and shorter end connections, but it is penalized by eddy-current loss at high speed, has a very limited transient overload power, and has a high uncontrolled generator voltage. The IPM motor shows the better performance compromise, but it might be more complicated to be manufactured. Analytical relationships are first introduced and then validated on three example designs and finite element calculated, accounting for core saturation, harmonic losses, the effects of skewing, and operating temperature. The merits and limitations of the three solutions are quantified comprehensively and summarized by the calculation of the energy consumption over the standard New European Driving Cycle.

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Comparison of Induction and PM Synchronous Motor Drives for EV Application Including Design Examples

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Vector Control And Dynamics Of Ac Drives

Electric vehicles make use of permanent-magnet (PM) synchronous traction motors for their high torque density and efficiency. A comparison between interior PM and surface-mounted PM (SPM) motors is carried out, in terms of performance at given inverter ratings. The results of the analysis, based on a simplified analytical model and confirmed by finite element (FE) analysis, show that the two motors have similar rated power but that the SPM motor has barely no overload capability, independently of the available inverter current. Moreover, the loss behavior of the two motors is rather different in the various operating ranges with the SPM one better at low speed due to short end connections but penalized at high speed by the need of a significant deexcitation current. The analysis is validated through FE simulation of two actual motor designs.

/pdf/performance-comparison-between-surface-mounted-and-interior-4k2491r5jx.pdf

Performance Comparison Between Surface-Mounted and Interior PM Motor Drives for Electric Vehicle Application

The design of ferrite-assisted synchronous reluctance machines is investigated, with particular attention to the pivotal aspect of avoiding irreversible demagnetization. Geometric rules for obtaining a robust design are proposed and described analytically. The safe operating area is quantified in terms of the corresponding maximum electrical loading. Such demagnetization limit is dependent on the operating temperature and the machine size. Furthermore, the comparison between the continuous load and demagnetization conditions shows that small- and medium-sized machines can be stiffer against demagnetization, with respect to larger machines, and have room for transient overload. The analysis is validated by finite elements, and a design example is given, namely, a 12-pole direct-drive machine, rated 910 $\hbox{N}\cdot\hbox{m}$ at 200 r/min.

Design of Ferrite-Assisted Synchronous Reluctance Machines Robust Toward Demagnetization

This paper presents a technique to modify the rotor lamination of a permanent-magnet-assisted synchronous reluctance motor, in order to reduce the magnet volume with no side effect on performance. A closed-form analysis, which is based on a lumped parameter model, points out that the magnet quantity can be minimized with a significant saving of material volume and cost. At a second stage, the risk of demagnetization is evaluated since the minimized magnets are thinner than the starting ones and work on lower load lines in their respective B-H planes. A feasible drawing is analytically defined, which is robust against demagnetization at overload, showing that the saving of magnet quantity depends on the maximum current overload and can be significant. The theoretical formulation is validated with finite-element analysis and experiments on a prototype machine.

/pdf/permanent-magnet-minimization-in-pm-assisted-synchronous-135if56rmh.pdf

Permanent-Magnet Minimization in PM-Assisted Synchronous Reluctance Motors for Wide Speed Range

The design of multipolar ferrite-assisted synchronous reluctance (FASR) machines is formalized via a two-step procedure At first, one rectified machine pole is analyzed, and key figures of merit are expressed in equations to derive general guidelines for high-performance designs Then, rotating machines are modeled as the combination of multiple rectified poles within a stack cylinder having constrained outer dimensions It is demonstrated that, at a given output torque, the number of poles can be optimized to minimize either the Joule loss or the magnet remanence The design approach is both finite-element analysis and experimental testing on an FASR machine, rated 795 $\hbox{N}\cdot \hbox{m} $ at 168 r/min It has been prototyped to compete with a previous solution based on rare-earth magnets, which shows similar performance

/pdf/multipolar-ferrite-assisted-synchronous-reluctance-machines-4ar9oregu5.pdf

Barbara Boazzo

Papers

Performance Comparison Between Surface-Mounted and Interior PM Motor Drives for Electric Vehicle Application

Comparison of Induction and PM Synchronous Motor Drives for EV Application Including Design Examples

Design of Ferrite-Assisted Synchronous Reluctance Machines Robust Toward Demagnetization

Permanent-Magnet Minimization in PM-Assisted Synchronous Reluctance Motors for Wide Speed Range

Multipolar Ferrite-Assisted Synchronous Reluctance Machines: A General Design Approach