PM Utilization Research Articles

Decoupling Analysis of Brushless Dual-Mechanical-Port Dual- Electrical-Port Machines

The brushless dual-mechanical-port dual-electrical-port (BLDD) machine has emerged as a promising alternative to the traditional mechanical continuously variable transmission (CVT), due to its gearless and brushless design. In BLDD machines, two sets of windings are placed in the same stator, and care must be taken to avoid strong coupling that may deteriorate the machine performance and reliability. This paper categorizes the topologies of existing BLDD machines into five types and presents a systematic decoupling analysis from the perspective of field-modulation theory. Using the presented method, the conditions to achieve decoupled designs are concluded and the decoupling characteristics of each type of BLDD machine are identified. Besides, a simple indicator is developed to fast identify the coupling type, i.e., decoupled, low or high coupling design, of BLDD machines, enabling an efficient selection of slot-pole combinations. With the aid of finite-element analysis (FEA), the coupling degree of BLDD machines with various slot-pole combinations has been analyzed for verification. Other performances, such as torque density and PM utilization, are also compared among the five types of BLDD machines to provide a more comprehensive view of their characteristics. Finally, a prototype of a BLDD machine is manufactured and tested to validate the analysis.

A Dual-Permanent-Magnet Machine With Asymmetric Stator Teeth-Tips

Dual-permanent-magnet machines (DPMMs) have attracted increasing attentions due to their merit of high torque density. Nevertheless, DPMMs suffer from low PM utilization ratio owing to large PM consumption. To improve the situation, this paper presents a DPMM with asymmetric stator teeth-tips, termed as AST-DPMM. The key of the proposed design is to arrange wide and narrow stator teeth-tips alternatively. By building an analytical model of the AST-DPMM, the impact of asymmetric stator teeth-tips is investigated. It is found the asymmetric stator teeth-tips can enhance the working harmonics by generating new magnetomotive force harmonics and permeance harmonics. Hence, it can achieve high torque density and improve PM utilization ratio simultaneously. The performance comparisons together with other machines are conducted to evaluate the investigated AST-DPMM. Finally, a prototype of the AST-DPMM is fabricated, and the experimental testing is conducted to verify the proposed ideas.

Comparative Analysis of Consequent-Pole PM Vernier Machines With Different Rotor Types

Taking advantage of flux modulation effects, consequent-pole PM vernier (CPMV) machines have been widely investigated recently, featuring high torque density and PM utilization ratio. However, the low-order harmonics of modulated flux fields additionally cause high iron saturation, which results in relatively low average torque under overload conditions, especially for the CPMV machines with an interior CPM (ICPM) rotor. Therefore, this paper proposes two hybrid CPM (HCPM) rotors of PMV machines to improve the overload performance by adding SPMs into the conventional ICPM rotor. First, the topologies of the proposed HCPM rotors are presented, named HCPM1 and HCPM2 rotors, respectively. Then the HCPM rotors and a conventional ICPM rotor with the V-shaped PM arrangement are designed and optimized to find out the optimal design parameters. Moreover, the electromagnetic performances including back-EMF, torque performance, efficiency, flux-weakening capability, and end effect are comprehensively investigated and compared. It indicates that the two proposed HCPM rotors both can generate equivalently high average torque, efficiency, and flux-weakening capability, compared to the conventional ICPM rotor. Furthermore, the proposed HCPM2 rotor can produce ≥22.9% higher torque at overload conditions. In addition, due to the bipolar PM arrangement, the unipolar flux leakage of the HCPM2 rotor is significantly reduced and lower than 0.05T. Finally, the prototype of a 12-stator-slot/ 20-rotor-pole CPMV machine with the HCPM2 rotor is manufactured to validate the finite element (FE) results.

Mover structure optimization and performance improvement for halbach consequent-pole PM synchronous linear motors with flux barrier

Aiming at the problems of large thrust ripple, low thrust density and magnetic leakage in the structure of Halbach consequent-pole PM synchronous linear motor, this paper proposes a flux barrier Halbach Consequent-Pole PM Synchronous Linear Motors (BHCP-PMSLM) by using the combination of unequal height PMs and air flux barrier. Firstly, after analyzing the structural magnetic leakage by the magnetic circuit method, the new motor structure proposed by adding an air flux barrier is used to suppress the magnetic leakage and to determine the structural shape of the air flux barrier. Secondly, the GA-ELM-GA algorithm was used to optimize the structural parameters of the motor with the optimization objectives of increasing thrust and reducing thrust ripple, the optimum motor structure parameters are obtained. Then, calculation and comparison of the electromagnetic characteristics of the new structure with three conventional PM synchronous linear motors with non-salient (NS-PMSLM) and Halbach consequent-pole (HCP-PMSLM). From the comparison results, the proposed structure has advantages, so the prototype was machined and experimented. The experimental results show that the optimization algorithm is effective, and the new structure increases the PM utilization by 41.1% and 7.4%, the thrust density by 5.3% and 12.1%, and the thrust fluctuation by 21% less than HCP-PMLSM compared to the conventional non-salient poles and Halbach consequent-pole.

Design Considerations of a New IPM Rotor With Efficient Utilization of PMs Enabled by Additive Manufacturing

Design Considerations of a New IPM Rotor With Efficient Utilization of PMs Enabled by Additive Manufacturing

Design and Performance Optimization of Flux-Focusing PMSMs With Consequent-Pole Rotor Considering PM Utilization Ratio

Design and Performance Optimization of Flux-Focusing PMSMs With Consequent-Pole Rotor Considering PM Utilization Ratio

Analysis of Contra-Rotating Brushless Integrated Flux-Modulation Machine With Open-Slot Structure for Wind Power Generation

This paper presents a contra-rotating (CR) brushless integrated flux-modulation (BIFM) machine with open-slot structure for wind power generation, termed CR-BIFM machine. The presented machine employs two contra-rotating rotors coupled with two sets of wind turbine blades, thus being able to capture more wind energy than conventional single-rotor wind turbines. Due to the dual flux-modulation effect and flux-bridge effect, the presented machine exhibits high torque/power density, making it suitable for direct-drive wind power generation without issues related to mechanical gearboxes. As two sets of windings share the same stator slots in the presented machine, the decoupling design of windings is systematically investigated from the perspective of air-gap modulated magnetic field, considering the influence of both stator and rotors. The advantages of the presented machine are comprehensively evaluated compared to the baseline machine, showing that the presented machine exhibits higher torque/power density, higher efficiency, higher power factor, higher PM utilization, and better vibration performance. Finally, a prototype is fabricated and tested to validate the analysis.

Torque Performance Enhancement for Hybrid PM Motor Considering Magnet Characteristic Difference and Variation

In this paper, for the hybrid permanent magnet (HPM) motor using multi PM materials as excitation sources, considering the characteristic difference and coupling effect between magnet materials, a preliminary design of the hybrid PMs is presented to improve the PM utilization and the superposition rate of torque components. Besides, according to the magnet characteristic variation under different operation conditions of the motor, a multi-objective variable condition weighted optimization design method is carried out to further improve the torque performance, efficiency and anti-demagnetization capability of HPM motor.

A novel tubular High-Power-Factor Transverse-Flux linear machine with Concentrated-Flux teeth

Due to principle constraints of the conventional transverse flux permanent magnet linear machine, its PM utilization is less than half. Besides, the complex structure and the serious magnetic leakage also lead to the limited thrust increase and the sharp decline of power factor. Therefore, the high-power-factor transverse-flux permanent-magnet linear machine (HPF-TFPMLM) using the concentrated-flux teeth is proposed in this paper. First, the topology and operation principle of the circumferentially distributed HPF-TFPMLM are investigated. The concentrated-flux teeth and multi-unit concentrated windings are introduced to improve power factor of the HPF-TFPMLM. To further study the proposed HPF-TFPMLM, its counterpart of the axial distributed topology is proposed for comparative analysis. Then, the key electromagnetic performance of power factor, thrust and thrust density of the HPF-TFPMLM are analyzed. Its performances including no-load EMF, magnetic field distribution and overload capacity are evaluated and compared with its counterpart. Finally, the feasibility and correctness of the investigated HPF-TFPMLM are verified.

Investigation of a Novel Linear Partitioned Primary Hybrid-excited Consequent-pole Flux-reversal Permanent Magnet Machine

This paper proposes a novel linear partitioned hybrid-excited consequent-pole flux-reversal machine featuring a wide flux adjusting range with less PM consumption. Due to the space confliction between armature and field windings in conventional hybrid-excited machine, the consequent-pole partitioned primary structure is employed to improve the PM utilization ratio and further enhance the flux regulation capability. Firstly, the topology, operation principle and flux regulation mechanism are introduced. Then, using finite element method (FEM), the dimensional parameters of the proposed machine and a conventional machine for comparison are globally optimized for higher thrust force and wider flux adjusting range. The electrical performance of optimized structures including open-circuit airgap flux density, open-circuit phase back-electromotive force (back-EMF), flux-adjusting capability and force characteristics are investigated. Furthermore, demagnetization and normal force are analyzed. Finally, a prototype is manufactured to validate the effectiveness of the proposed topology and analysis. The proposed machine is observed to have better flux regulation capability than conventional machine with improved PM utilization ratio, which means it is suitable for wide speed range system applications.

Design and analysis of a new field-modulated permanent magnet machine with an improved rotor

In this paper, a new field-modulated permanent magnet (FMPM) machine with an improved rotor is proposed and analyzed. The proposed FMPM machine enjoys the advantages of high PM utilization and better heat dissipation. For a fair comparison, the proposed FMPM machine is designed with the same geometrical parameters based on the existing FMPM machine. The electromagnetic performances of existing FMPM (E-FMPM) machine and proposed FMPM (P-FMPM) are compared and analyzed by using finite element method, verifying that the proposed FMPM machine with an improved rotor can obtain high torque density and high PM utilization.

A Novel Slot-PM-Assisted Consequent-Pole-PM Machine With Hybrid Magnets of Ferrite PMs and Rare Earth PMs

In this article, slot-PM-assisted consequent-pole-PM machine (SPMA-CPMM) is proposed. The key is that the consequent-pole ferrite PMs are employed in the stator yoke to reduce the PM material cost largely, while a small amount of tangential magnetized rare-earth PMs is placed in the slot opening to improve the torque production. This proposed hybrid magnet design can greatly enhance the PM utilization ratio and reduce the PM cost while maintaining a relatively large torque density. In this article, the configurations of ferrite-PM machine (FPMM), consequent-pole ferrite-PM machine (CFPMM), and SPMA-CPMM are illustrated, while equivalent magnetic circuits (EMCs) of them are compared. Then, the electromagnetic performances of three machines are investigated and compared, which verifies the validity of the proposed machine.

Investigation of a Novel Consequent-Pole Flux-Intensifying Memory Machine

This paper mainly focuses on the investigation and analysis of a novel consequent-pole flux-intensifying memory machine (CP-FIMM). The proposed CP-FIMM exhibits the advantages of a satisfactory flux-regulation range, reduction of the required magnetizing current magnitude, as well as similar torque with much less PM utilization compared to its conventional counterpart. By designing the q-axis flux barriers, the flux-intensifying structure can be realized to enhance the demagnetization withstand capability of the CP-FIMM. The machine topology and operating principle are described. Moreover, the equivalent magnetic circuit model is developed to highlight the performance improvement of the proposed CP-FIMM. Finally, the electromagnetic performance of the proposed CP-FIMM is compared with that of a benchmark conventional FIMM by 2-D and 3-D finite element analysis.

Research On Enhanced Harmonic Effect of a Dual-PM-Excited Flux-Modulated Motor

In this paper, an improved design for a dual-permanent-magnet-excited (DPME) motor is proposed, where the harmonic characteristics are newly introduced into the design process to enhance the harmonic effect. Based on the role that harmonics play in the torque generation process, not only the amplitude characteristics of harmonics are considered, but also the phase characteristics of harmonics are introduced, which is the key to improve PM utilization. In addition, the harmonics excited by stator PM (SPM) source or rotor PM (RPM) source are considered separately due to the unique dual-PM source characteristic of the DPME motor, which can further enhance the amplitude and phase characteristics of harmonics and then improve the PM utilization. Firstly, the dominant harmonics excited by SPM or RPM are picked out with the analysis of amplitude characteristics. Then, by taking into account the phase characteristics, the effective harmonics excited by SPM or RPM are selected within the dominant harmonics and serve as design objectives. After that, a collaborative design can be realized with the parameters and the two harmonic characteristics of effective harmonics. Finally, the electromagnetic performances are investigated by the Finite Element Analysis (FEA), and the results verify the effectiveness of the design considering harmonic characteristics of dual-PM sources.

Analysis of Split-Tooth Stator-Slot Permanent-Magnet Machines With Different PM Arrangements

In this paper, the split-tooth stator-slot permanent-magnet (ST-SSPM) machines with different PM arrangements are comprehensively analyzed. Four types of ST-SSPM machines are first introduced and classified by the positions and polarities of PMs. Then, the operation principles are elaborated and the slot-pole combinations are derived from the view of field modulation theory. Besides, four types of ST-SSPM machines with different slots and rotor poles are globally optimized to achieve maximum torque and minimum torque ripple. Furthermore, the electromagnetic performances of the optimal designs are thoroughly analyzed by using the finite-element analysis (FEA), including the cogging torque, back-EMF, steady torque, PM utilization ratio, loss, efficiency, and PM demagnetization. Finally, some conclusions are drawn based on the optimal designs and analyzed results.

Comparative study of partitioned stator flux-modulation motors with different permanent magnet arrays

By incorporating the merits of partitioned stator and flux modulation techniques, the partitioned stator flux modulation motors featuring high torque, have attracted much attention. This paper investigates four partitioned stator flux modulation motors with different types of PM arrays, including surface-mounted type, consequent-pole type, Halbach-array type, and half-Halbach type. The influences of key parameters on the average electromagnetic torque is conducted and compared. Then, based on the optimal designs, four motors are compared in terms of magnetic field distribution, back-electromotive force, torque characteristics, loss and overload ability. The result reveals that the half-Halbach motor is capable of utilizing more PM to improve electromagnetic torque. Also, the consequent-pole motor achieves the highest torque per PM usage. In addition, performance comparison under the same PM usage is carried out. The result shows that the half-Halbach motor not only exhibits the highest average torque but also achieves the highest PM utilization. Last, the prototype of half-Halbach motor is built for experimental verification.

Comparative Study of Electromagnetic Performance of Stator Slot PM Machines

This paper firstly explains how the stator slot PM (SSPM) machines have evolved from the conventional flux reversal PM machines (FRPMs), by placing the magnets over the tooth tips or between the tooth tips. The influence of tooth tips and PM configurations of five types of SSPM machines with various PM structures in stator slots, two with tooth tips and three without tooth tips, on the electromagnetic performance are then investigated and compared. It shows that, no matter what winding configurations (non-overlapping windings or overlapping windings), appropriate design of tooth tips can increase the average torque, the SSPM machines having flux focusing structures (i.e. Halbach array PM and spoke array PM) exhibit higher torque than those without flux focusing, and the SSPM machines with tooth tips have higher PM utilization rate than those without tooth tips. Non-overlapping windings can help provide higher torque density when the prototype machine length is less than around 125mm while overlapping windings are more advantageous if the machine length is over 125mm.

Torque Performance Improvement of Consequent-Pole PM Motors With Hybrid Rotor Configuration

Both the consequent-pole permanent magnet (CPM) motor and the spoke-type PM motor have the potential to reduce the consumption of PMs while suffering from the high-torque pulsation. This article proposes a new hybrid rotor CPM motor, in which the hybrid rotor is composed of consequent-pole surface-mounted PM (SPM) modules and spoke-type PM rotor modules. Compared with the existed hybrid rotor CPM motor with half of spoke-type PM rotor modules, the whole of spoke-type PM rotor modules and their shifting are capable to adjust the harmonics of the rotor-MMF, which is the benefit to improvement of the torque performances. To obtain high-torque performances and low PM volume, multiobjective optimization is employed to optimize the key parameters. Afterward, the proposed motor is compared with three PM motors. The results show that, compared with the SPM motor, the proposed CPM motor offers high PM torque and PM utilization ratio, such as other CPM motors. Besides, the torque pulsation is reduced significantly compared with the traditional CPM motor. Hence, the proposed motor offers a high PM utilization ratio and low-torque pulsation simultaneously. Through the finite element method (FEM) analysis and experimental test, the merits of the proposed hybrid CPM motor are verified.

Highly efficient double plasma mirror producing ultrahigh-contrast multi-petawatt laser pulses.

We present a highly efficient double plasma mirror (DPM) that provides ultrahigh-contrast multi-petawatt (PW) laser pulses with a temporal contrast ratio reaching 1017 up to 160 ps and 1012 up to 2 ps before the main pulse. The high reflectivity of 70%, along with the high-contrast enhancement factor of 700,000, was achieved from the DPM installed after the final stage of a 4 PW Ti:sapphire laser. The 4 PW laser was equipped with cross-polarized wave generation and optical parametric chirped-pulse amplification stages for initial high-contrast operation. The DPM operation was undertaken with conditions that did not modify the spatiotemporal profiles of incident multi-PW laser pulses. This highly efficient DPM with the high-contrast enhancement promises the utilization of multiple PMs as a practical rear end for upcoming tens of petawatt lasers to achieve ultrahigh temporal contrast.

Which Device Is Favorable for Intubation Attempts of Pediatric Residents on Four Different Pediatric Airway Simulations?

Endotracheal intubation is an essential skill for the pediatric airway management. Although direct laryngoscopy (DL) is the standard method, several videolaryngoscopes (VLs) have been recently enhanced as an alternative especially for difficult intubations. We aimed to compare McGrath MAC (McG) and Storz C-MAC PM (ST) VLs with DL in terms of intubation success rate, time to intubation (TTI), and duration of obtaining glottis view of intubation attempts performed by pediatric residents on different pediatric airway manikins. The pediatric residents with no experience in videolaryngoscopy were included. After a brief demonstration, intubation attempts with 3 randomly handled different devices with 6 different blades were performed on a child manikin, an infant manikin, a Pierre-Robin sequence infant manikin, and a child manikin with cervical immobilization sequentially. Fifty pediatric residents were enrolled. The attempts of DL on child manikin and attempts of all devices on child with cervical immobilization simulation were completely successful. For the attempts on both infant manikin and Pierre-Robin sequence infant manikin, the success rate of McG was significantly lower than ST and DL (P = 0.011 and P = 0.001). In the child manikin, McG and ST had prolonged TTI compared with DL (P = 0.016 and P = 0.001). For the child with cervical immobilization simulation, TTI of DL was significantly shorter than McG and ST (P = 0.011 and P = 0.001). Time to intubation of McG was significantly longer than DL and ST for the attempts on both 2 infant manikins. The rate of Cormack-Lehane grade I glottis view was similar for the attempts on both 2 child airway simulations. For infant manikin and Pierre-Robin sequence infant simulation, the rate of Cormack-Lehane grade I of ST was higher than attempts of DL and McG. The attempts of pediatric residents on infant normal airway and Pierre-Robin sequence infant airway simulations resulted with enhanced glottis view by the utilization of Storz C-MAC PM, but both 2 VLs did not provide the improvement of intubation success rate and TTI compared with DL on these 4 different pediatric manikins. Further clinical studies of different VLs in different clinical courses are required for a reliable utilization in children.