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This work investigates the effect of design parameters of permanent magnet (PM) and flux barriers (FBs) in the rotor on the anti-demagnetization ability (ADA) of fractional slot concentrated windings interior permanent magnet (IPM) motors for electric scooters. A 2.5 kW IPM motor (12 slots and 8 poles) is designed for a wide speed range, and its ADA associated with different PM and FB arrangements is studied under high temperature and high current density operations. The analysis shows the relationship between the ADA and characteristic current (Ich, defined as the ratio of PM flux linkage to d-axis inductance). It is also found that proper designs of flux barriers can significantly improve the ADA of the IPM motor without much affecting Ich. Thus, the motor ADA and performance can be simultaneously improved. Finite element analysis is used for evaluation, and experiments are conducted to validate the analysis.

This article presents an analysis on the field weakening capability of a flux intensifying synchronous motor (FI-SM) with a small quantity of inset permanent magnets (PMs) on the rotor surface. Differing from other FI-SMs whose rotors are constructed by interweaving PMs and flux barriers (FBs), for the presented FI-SM, the PM dimensions can be easily adjusted without significantly altering the rotor configuration, thus offering more flexibility in rotor design and making it more feasible to analyze the influence of the added PM on flux density distribution, inductances, PM flux linkage, and field weakening capacities in conjunction with armature current. This article, through investigating this design potential, aims to provide an approach for design and analysis of this type of motor to enhance the performance and improve the field weakening capability. Experiments are conducted to validate the simulation.

This paper proposes a control strategy to enhance the operating efficiency of a Hybrid Energy Storage System (HESS) for an Interior Permanent Magnet Synchronous Motor (IPMSM) drive. In this method,...

This paper proposes a novel rotor position estimation technique based on stator flux linkage to implement robust sensorless field-oriented control for permanent magnet synchronous motor drives. The proposed method can accurately estimate rotor position by mitigating the dependence on quality of the magnitude and phase angle of the estimated stator flux linkage. A high-accuracy load angle calculation based on $d$ - $q$ -axis current estimation method is first developed for further rotor position determination. In the rotor position calculation, the reference flux linkage magnitude is used instead of the estimated one to avoid the influence of potential high noise levels during low speed operation. As a result, the rotor angle estimation depends only on the phase angle of stator flux linkage, without the effect of its magnitude. The estimation accuracy can thus be improved. Also, by employing a simple stator flux linkage phase lag compensator, the performance of the proposed sensorless method can be dramatically improved at low speed. Moreover, the problem of motor parameter variation (e.g., changes in winding resistance, stator inductances, and permanent magnetic flux linkage) has been analyzed and overcome. Finally, comparisons between conventional and proposed methods are presented with simulations and experiments to demonstrate the effectiveness and reliability of the proposed method.

This paper investigates the flux intensifying (FI) feature of permanent magnet assisted synchronous reluctance motor (PMa-SynRM) in order to achieve high torque density with a small amount of permanent magnet (PM). This motor is thus denoted “FI-PMa-SynRM”. The performance of the developed FI-PMa-SynRM is compared with that of two other counterparts, i.e., an inset surface permanent magnet synchronous motor (SPMSM) and a synchronous reluctance motor (SynRM) to highlight the strengths of the FI-PMa-SynRM. In addition, an analysis on partial demagnetization and torque density of the developed FI-PMa-SynRM is conducted to demonstrate its advantages. The finite element method (FEM) is employed for the analysis in terms of flux linkage and inductances so that the effectiveness of the FI characteristics is validated. The analysis shows that a high torque density (24.79 Nm/L or even greater) can be achieved with a small amount of PM (0.72% motor volume). The ability of anti-demagnetization is also fulfilled. Furthermore, experimental results are provided to validate the analysis findings.

This paper investigates the demagnetization problem of permanent magnets for permanent magnet-assisted synchronous reluctance motors (PMa-SynRM) and applies “demagnetization ratio” as an index to evaluate demagnetization of permanent magnet (PM). The PMa-SynRM is often designed with multilayer flux barriers to improve saliency and reluctance torque in the rotor. Weaker or less PM (than that for interior PM motors) is embedded into the rotor which could be demagnetized in high-performance operation. PM demagnetization involves temperature, current magnitude, current phase angle, designed PM operating point, or combined effect of the above factors. This work investigates the demagnetization risk for PMs in all the layers of PMa-SynRM rotor considering these factors. In particular, the current phase angle for flux weakening operation is often omitted in demagnetization analysis. First, the motor performance to satisfy the operation condition over a wide speed range is analyzed and the proportion of motor torque components, i.e., reluctance torque and electromagnetic torque, considering temperature is investigated. Then, the flux density distributions on PMs at each position/layer are studied and the PM operating points are obtained based on the variation of excitation current, current phase angle, and temperature in order to evaluate the demagnetization risk. The analysis suggests that the high current phase angle combining the effect of high temperature is the major cause of irreversible demagnetization. Finally, a method incorporating the index “demagnetization ratio” is proposed to redesign the PMa-SynRM to avoid demagnetization. Experiments are conducted to validate the simulation.

This paper proposes a flux-intensifying permanent magnet-assisted synchronous reluctance motor (FI-PMa-SynRM) using surface-inset permanent magnet (PM) instead of embedded PM in the rotor. The proposed FI-PMa-SynRM employs a small amount of PM that is inset on the rotor surface facing $d$ -axis instead of facing $q$ -axis as in common PMa-SynRMs. It also differs from conventional flux-intensifying interior PM motor, where the PM is embedded inside the rotor. The proposed motor enables making use of the arrangements of two types of flux barriers (FBs): the cutoff FB and the magnet FB, collectively referred to the outer FBs, to enhance the torque output and reduce the torque ripple. The first objective in this paper is to explain the principles of the proposed FI-PMa-SynRM, and the second is to analyze the proposed technique for enhancement of the torque output with small PM volume while keeping the lowest possible torque ripple. The finite-element analysis is employed to validate the proposed motor and analyses, and the results demonstrate their advantages and effectiveness.

This paper proposes a simple method to generate stable voltage commands for permanent magnet synchronous motors to achieve low torque ripple based on space vector modulation direct torque control (SVM-DTC). The relationship between applied voltage and electromagnetic torque is first analyzed and the effect of the voltage and flux linkage on torque ripple is discussed. Then, the new method is developed to reduce torque ripple by giving low-fluctuation voltage commands to the voltage source inverter. The magnitude of the voltage command is calculated by avoiding the effect of flux linkage angle that can be estimated inaccurately during motor operation. Therefore, the fluctuation of the voltage command can be significantly reduced. In order to validate the proposed method, Simulink is first used for simulation and the performance of the proposed method is evaluated. It is found that the torque ripple can be substantially reduced while keeping a low switching frequency and improving system response. Then, a hardware-in-the-loop (HIL) technique is applied to test the developed algorithm that is written into a Texas Instruments microcontroller. This validates the simulation results and the proposed method.

The paper aims to provide a guideline for rotor design of permanent magnet (PM) assisted synchronous reluctance machine (PMa-SynRM). Unlike interior PM machines, the PMa-SynRM is essentially an SynRM with dominant reluctance torque. The PMa-SynRM is often designed by directly embedding magnets into an SynRM rotor to improve the performance. However, how the PMs can be arranged in the rotor to enhance motor performance has not been fully discussed. This paper investigates the influence of several key factors concerning the PM arrangements, including number of PM layers, inserted positions, and PM sizes. The torque, flux linkages, power factor, and motor performance are comprehensively evaluated. Based on the analysis, a brief guideline is suggested for PMa-SynRM rotor design. Finite element analysis is used for evaluation and experiments are conducted to validate the analysis.

The innovative rotating looped thermosyphons (RLTs) with and without a coil insert were proposed with cooling applications in rotating machinery. The spatial gradients of body forces among the vapor–liquid mixture of the distilled water in a strong centrifugal acceleration field motivated the flow circulation in a RLT to facilitate the latent heat transmissions. The effective thermal conductivity (Keff), the thermal resistance (Rth), the Nusselt numbers in the condenser (Nucon) and evaporator (Nueva), and the Nusselt number of the airflow induced by the rotating bend of the condenser (Nuext,con) of each RLT were measured at various rotating speeds and heat powers with two filling ratios of 0.5 and 0.8. The increase of filling ratio from 0.5 to 0.8 to maintain a thin liquid film along the rotating inner leg of each RLT substantially improved the heat transfer performances. The Keff, Nucon, Nueva, and Nuext,con were increased with rotating speed, leading to the corresponding reduction of Rth. On the basis of the experimental data, the empirical correlations that were used to calculate Rth, Keff, Nucon, Nueva, and Nuext,con of the RLTs at the two filling ratios with and without coil were proposed to assist the relevant design applications.

This paper presents a C-rate control method for a battery/supercapacitor (SC) hybrid energy storage system (HESS) to enhance the life cycle of the battery in electric vehicles (EVs). The proposed HESS provides satisfactory power for dynamic movements of EVs (e.g., acceleration or braking) while keeping the battery current within a secure level to prevent it from degradation. The configurations of conventional HESSs are often complex due to the two energy storages and their current/voltage sensing involved. Therefore, in this paper, a simple current-sensing scheme is utilized and the battery is directly treated as a controlled variable to help the battery output current remain stable for different load conditions. While the proposed circuit requires only one current feedback signal, neither the SC nor load current sensors are needed, and the circuit design is thus significantly simplified. Both simulation and experimental results validated the effectiveness of the proposed HESS operating in conjunction with the motor drive system. The proposed method aims at fully utilizing recycled energy and prolonging battery lifespan.

This work analyzes and compares the performances of permanent-magnet-assisted synchronous reluctance machines (PMa-SynRM) and interior permanent magnet synchronous machine (IPMSM) on their constant power speed range (CPSR) capability for electric vehicle (EV) applications. The CPSR is a key performance index for traction motors to achieve wide speed range where the IPMSM is known to be an excellent candidate. However, a recent trend for traction motor development is to reduce the amount of rare earth magnet used due to its high cost and possible supply uncertainty. As an alternative, the PMa-SynRM possesses a higher saliency (thus higher reluctance torque) and lower PM quantity (thus lower PM torque) compared to IPMSMs. With the same power or torque output, the major distinction between these two types of machines would be the proportions of different torque components (PM and reluctance torques) due to rotor designs. The distinctive rotor designs would significantly affect the CPSR and this needs to be investigated for traction motor designs and various EV applications. Five 10 kW-30 Nm/L designs, with three IPMSMs and two PMa-SynRMs are studied. The analysis results show that the PMa-SynRMs can achieve higher peak speed despite the torque and power are lower at high speed. In contrast, the IPMSM can maintain the power beyond the base speed to achieve superior CPSR but the power drops quickly to zero at high speed. The high efficiency region appears at the mid speed range for the IPMSM but at high speed region for the PMa-SynRM due to their different PM and reluctance torque profiles. Two prototypes were tested, one being IPMSM and the other PMa-SynRM to validate the analysis results.

In this paper, a study was conducted using a unit equivalent magnetic circuit (EMC) in correlating the relationship between the magnet thickness, the modulating ring pole-piece thickness, and their circumferential pitch. A numerical optimization method is employed in selecting the optimum ratio of the magnet to pole-piece thickness. The study reveals the need to simultaneously consider these parameters during the design of a magnetic gear electric machine because of their strong mutual dependency. A finite element analysis (FEA) was conducted using the optimum ratios. The results correspond to those of the EMC. Also, the performance of the machine is analyzed and found to have a power factor of 0.78. To further verify the results of FEA, a prototype was built using the same configurations of the FEA model. Measurements taken from the prototype are on par with the simulated results.

This paper investigates and evaluates the correlation between the rotor magnet configurations and the characteristics and performance of a high-speed micro-turbine generator. Four configurations designed and studied include ring, segmented, modular, and asymmetric magnet shapes. The rotor is often manufactured by pre-magnetized permanent magnets (PMs), in which the magnets would be damaged when being assembled into the sleeve due to compressive force and magnetic force in some manufacturing process. Therefore, post assembly magnetization is applied to magnetize the PMs after the rotor being assembled into the sleeve. The effectiveness of this technique for different rotor configurations is firstly investigated. Then, the harmonic spectrums of back EMF, air-gap flux density, and cogging torque are evaluated. The relation among cogging torque, the vibration, noise and mechanical stress in these magnet configurations are analyzed. Finally, the generator performance is evaluated and discussed in the different resistance load conditions. Finite element analysis (FEA) is used to evaluate and validate the analysis results.

This paper explores the system response of motor drive systems using wide band gap silicon carbide (SiC) transistors. A SiC power transistor-based voltage source inverter with field-oriented control is established by using MATLAB/Simulink for permanent magnetic synchronous motor. Based on simulation results, the findings are that increasing switching frequency significantly improves dynamic response of speed and that the total harmonic distortion of the three-phase current can also be improved.

This paper presents the comparison of the performance of a novel flux intensifying permanent magnet (PM) assisted synchronous reluctance motor (FI-PMa-SyRM) with different rotor surface layouts. A SynRM without embedded PM is also considered. This paper strengthens and completes a previous work where this novel FI-PMa-SynRM was proposed. With the analysis and comparison, the advantages of FI-PMa-SynRM are highlighted.

This paper analyzes the characteristics of an electric vehicle traction motor unit combining an interior permanent magnet (PM) synchronous motor and PM-assisted synchronous reluctance motor. Their individual operational characteristics are first investigated. The effective combination of the two motors to achieve a wide constant power speed range (CPSR) is also evaluated. The Urban Dynamometer Driving Schedule driving cycles are used to evaluate the combined traction unit. Simulation results reveal that the control strategy would be different for the two types of motors to show the advantages of this combination. The designs to achieve a high CPSR are also suggested.