This paper systematically covers the significant developments of the last decade, including surrogate modeling of electrical machines and direct and stochastic search algorithms for both single- and multi-objective design optimization problems. The specific challenges and the dedicated algorithms for electric machine design are discussed, followed by benchmark studies comparing response surface (RS) and differential evolution (DE) algorithms on a permanent-magnet-synchronous-motor design with five independent variables and a strong nonlinear multiobjective Pareto front and on a function with eleven independent variables. The results show that RS and DE are comparable when the optimization employs only a small number of candidate designs and DE performs better when more candidates are considered.

A Review of Recent Developments in Electrical Machine Design Optimization Methods With a Permanent-Magnet Synchronous Motor Benchmark Study

The high-speed (HS) electric machines are gaining attention in several different applications, and the development of advanced materials, electronic components, and control algorithms is pushing ahead the technological speed limits. In the electromagnetic sizing of HS machines, the mechanical and thermal involvements are very tight to make it necessary to deal with all the different aspects at the same time. This paper aims to summarize and discuss the electrical and the mechanical aspects involved in the HS machine design, highlighting the main issues and the tradeoffs that the designer has to consider. Furthermore, the correlation between volume reduction and speed increase, based on commercial high-frequency rotor-stator units, is also presented.

Electrical Machines for High-Speed Applications: Design Considerations and Tradeoffs

Several factors including fossil fuels scarcity, prices volatility, greenhouse gas emissions or current pollution levels in metropolitan areas are forcing the development of greener transportation systems based on more efficient electric and hybrid vehicles. Most of the current hybrid electric vehicles use electric motors containing powerful rare-earth permanent magnets. However, both private companies and estates are aware of possible future shortages, price uncertainty and geographical concentration of some critical rare-earth elements needed to manufacture such magnets. Therefore, there is a growing interest in developing electric motors for vehicular propulsion systems without rare-earth permanent magnets. In this paper this problematic is addressed and the state-of-the-art of the electric motor technologies for vehicular propulsion systems is reviewed, where the features required, design considerations and restrictions are addressed.

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Rare-earth-free propulsion motors for electric vehicles: A technology review

The rotor overtemperature caused by losses is one of the important issues for the high-speed electric machine. This paper focuses on the loss analysis and thermal performance evaluation for a rotor of 100 kW, 32 km/min high-speed permanent-magnet motor. The rotor temperature distribution based on the finite element method is obtained by accounting for various losses, including air-friction loss of the rotor, iron loss of the active magnetic bearing, and eddy-current loss of the motor. The influence of the stator core temperature on rotor thermal performance is analyzed by using a coupling simulation of fluid-temperature field. The temperature rise measurement of rotor is employed to study the impact of different cooling way on rotor thermal performance and to verify the computational accuracy of losses and temperature distribution. The analysis result of air-friction loss is compared with the measurement, which is obtained from the total losses by using the method of loss separation. It has great significance for the cooling structure design and the efficiency enhancement of electrical machine.

Loss Calculation and Thermal Analysis of Rotors Supported by Active Magnetic Bearings for High-Speed Permanent-Magnet Electrical Machines

Permanent magnet (PM) type transverse flux linear motors (TFLMs) are electromagnetic devices, which can develop directly powerful linear motion. These motors have been developed to apply to high power system, such as railway traction, electrodynamics vibrator, free-piston generator, etc. This paper presents an optimum design of a PM-type TFLM to reduce the weight of motor with constraints of thrust and detent force using response surface methodology (RSM) and genetic algorithms (GAs). RSM is well adapted to make analytical model of motor weight with constraints of thrust and detent forces, and enable objective function to be easily created and a great computational time to be saved. Finite element computations have been used for numerical experiments on geometrical design variables in order to determine the coefficients of a second-order analytical model for the RSM. GAs are used as a searching tool for design optimization of TFLM to reduce the weight of motor and improve the motor performance.

Design Optimization of Transverse Flux Linear Motor for Weight Reduction and Performance Improvement Using Response Surface Methodology and Genetic Algorithms

This paper deals with a 44pole-48slot fractional slot concentrated winding permanent magnet synchronous machine (FSCW PMSM) for a low-speed direct drive. Two different rotor topologies, a surface permanent magnet (SPM) rotor and a consequent pole (CP) rotor, are optimized and compared both analytically and experimentally. The experimental results confirmed that an FSCW PMSM with a CP rotor can achieve almost equivalent performance at the rated state when compared to an FSCW PMSM with an SPM rotor with 33% less permanent magnet material.

Fractional Slot Concentrated Winding PMSM With Consequent Pole Rotor for a Low-Speed Direct Drive: Reduction of Rare Earth Permanent Magnet

The permanent magnet vernier machine (PMVM) is known to be well suited for direct drive applications due to its high torque characteristics at low speed. This paper introduces a novel design of PMVM comprising a modular stator and a consequent pole rotor. The proposed design magnetically decouples each phase and suppresses the magnetic unbalance caused by the consequent pole rotor.

A Novel Design of Modular Three-Phase Permanent Magnet Vernier Machine With Consequent Pole Rotor

As accomplishing the research of the PM synchronous motor driven by 15 kW at the rated speed of 120,000 rpm, this paper represents an approach to minimize eddy current losses which occur prominently at high speed. Various simulation and testing techniques are therefore applied to determine the effect of design parameters. Here, the proposed parameters for analysis are winding types, slot opening width and sleeve thickness. This paper based on the obtained results, evaluates the optimum value of the most critical design parameters responsible for eddy current loss. Finally, this paper studies the developed model which represents a solution for minimizing the cause of eddy current loss by implementation of sinusoidal distribution of air-gap magnetic flux density. It comes to the conclusion that sleeve thickness should be chosen as considering a function of mechanical stress and critical speed of rotor. Furthermore, the critical speed of rotor is evaluated by rotor dynamics. The design efficiency is well accorded with the efficiency test, having a maximum error of 2.7%.

Ultra High Speed Motor Supported by Air Foil Bearings for Air Blower Cooling Fuel Cells

Fractional slot concentrated winding permanent magnet synchronous machines (FSCW PMSMs) are suited for low speed direct drive since they offer comparatively large number of poles, high torque density, and low torque ripple. This paper introduces feasibility study on FSCW PMSMs with consequent pole (CP) rotor for low speed direct drive. A 40 pole-48 slot FSCW PMSM with CP rotor is analyzed and characterized by extensive 2-D finite-element analysis. The analysis reveals the proposed topology can achieve good performance.

Fractional Slot Concentrated Winding Permanent Magnet Synchronous Machine With Consequent Pole Rotor for Low Speed Direct Drive

Permanent magnet (PM)-type transverse flux linear motors (TFLMs) are electromagnetic devices which can develop directly powerful linear motion. The unique configuration makes power of output higher than longitudinal motors, but also it makes characteristic analysis difficulties. This paper deals with an effective analysis of PM-type TFLM by 3-D equivalent magnetic circuit network method (EMCNM). This paper presents optimum design of PM-type TFLM to reduce the weight of the machine with the constraints of thrust and detent force using response surface methodology (RSM). RSM was well adapted to make the analytical model of the minimum weight with constraints of thrust and detent forces and enable the objective function to be easily created and a great deal of the time in computation to be saved. Therefore, it is expected that the proposed optimization procedure using RSM can be easily utilized to solve the optimization problem of electric machines.

Do-Kwan Hong

Papers

Fractional Slot Concentrated Winding PMSM With Consequent Pole Rotor for a Low-Speed Direct Drive: Reduction of Rare Earth Permanent Magnet

A Novel Design of Modular Three-Phase Permanent Magnet Vernier Machine With Consequent Pole Rotor

Ultra High Speed Motor Supported by Air Foil Bearings for Air Blower Cooling Fuel Cells

Fractional Slot Concentrated Winding Permanent Magnet Synchronous Machine With Consequent Pole Rotor for Low Speed Direct Drive

Optimum Design of Transverse Flux Linear Motor for Weight Reduction and Improvement Thrust Force Using Response Surface Methodology