Consequent-pole Permanent Magnet Research Articles

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.

Design and Research of Novel Consequent-Pole Dual PM Vernier Machines with Spoke and Halbach Array

Design and Research of Novel Consequent-Pole Dual PM Vernier Machines with Spoke and Halbach Array

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.

Comparative Study of Field Modulation Effects in Consequent-Pole PM Machines With Different Stator Slot Configurations

Comparative Study of Field Modulation Effects in Consequent-Pole PM Machines With Different Stator Slot Configurations

Design and Analysis of Consequent-Pole Permanent Magnet Vernier Motor With Cancellation of Even-Order Harmonics

Design and Analysis of Consequent-Pole Permanent Magnet Vernier Motor With Cancellation of Even-Order Harmonics

A Novel Flux Concentrated Stator Consequent-Pole Permanent Magnet Machine With Nonuniform Stator Modulation Teeth

A Novel Flux Concentrated Stator Consequent-Pole Permanent Magnet Machine With Nonuniform Stator Modulation Teeth

Influences of Magnet Arrangements on Air-Gap Field Modulation Effects in Interior Consequent-Pole PM Machines

This article comprehensively investigates and compares the influences of permanent magnet (PM) arrangements on air-gap field modulation effects (AFMEs) in interior consequent-pole PM (ICPM) machines. Four typical single-layer PM structures, i.e., flat-type, spoke-type, U-shaped, and V-shaped magnet designs, are exemplified in order to identify how different rotor structures perform AFMEs due to a double-side slotting and affect the torque behavior. The contributed torque components and corresponding torque proportions of the main air-gap flux density working harmonics are quantificationally distinguished by adopting the Maxwell stress tensor (MST) method. It shows and confirms a fact that the flat-type and V-shaped ICPM cases present the lowest and the highest torque proportions due to their AFMEs, respectively. In addition, the influences of rotor PM parameters on AFMEs of the four single-layer ICPM machines are subsequently studied. Finally, the prototype of the ICPM machine with V-shaped PM structure is manufactured. The corresponding experimental results are conducted to validate the theoretical and finite element (FE) analyses.

Investigation of Flux-Modulating Consequent Pole Motors

This article investigates the electromagnetic performance of a novel variable-flux permanent magnet (PM) motor, named the “flux-modulating consequent pole motor (FCM),” through finite element analysis (FEA) and experiments. The FCM is a combination of a flux-modulating (FM) motor and a consequent-pole PM motor, whose torque can be generated from both the FM and PM motors without causing unbalanced magnetic forces (UMFs). Two models with 16 and 20 poles are used to analyze the torque, efficiency, and power factor of the FCM. Moreover, efficiency maps of the FCM are compared with those of the conventional PM synchronous motors. It is revealed that the torque of the FCM depends on the values of winding factors of the FM and PM motors. Finally, experimental results on a 20-pole prototype machine are presented to validate the operating principle of the FCM and the FEA simulations.

Reduction of Unipolar Leakage Flux and Torque Ripple in Consequent-pole PM Vernier Machine

This paper proposes a new consequent-pole permanent magnet vernier machine (CPMVM), which can be regarded as a combination of two conventional CPMVM with opposite polarities. Based on the simplified axial magnetic circuit model, it is verified that the proposed CPMVM can reduce the unipolar leakage flux. In order to reduce the torque ripple of machine and improve the output torque of machine, the flux barrier is placed on the rotor of the proposed machine. Then, the parameters of the proposed CPMVM are optimized and determined. Moreover, the electromagnetic performance, including no-load air-gap flux density, average torque and torque ripple, flux linkage, back-electromotive force, cogging torque, average torque, torque ripple, power factor and loss, is compared with conventional surface-mounted permanent magnet vernier machine (SPMVM) and CPMVM. Finally, it is demonstrated that proposed CPMVM with flux barrier can effectively reduce the unipolar leakage flux and greatly reduce the torque ripple of machine. Also, compared with the SPMVM, the proposed CPMVM with flux barrier saves more than 45% of the permanent magnet material without reducing output torque.

Analysis of Dual PM Vernier Machines With Different Consequent-Pole PM Topologies

In order to further improve the torque density of flux modulation machines, two novel dual-PM vernier machines (DPMVMs) with two PM pieces and two ferromagnetic iron poles on each stator tooth are proposed in this paper. Together with two conventional DPMVMs, four types of DPMVMs with different consequent-pole PM topologies are comprehensively investigated and compared. The working harmonics and the dominating harmonics that contribute to torque production of four machines are analyzed. Aiming at maximum torque, four machines are all optimized and their electromagnetic performances in terms of cogging torque, back-EMF, rated torque, overload capability, power factor, loss, and efficiency are evaluated and compared using finite element (FE) method. Finally, a prototype is fabricated and tested. The experimental results have validated the theoretical analysis.

Design and Evaluation of Reduced-Rare-Earth Interior Consequent-Pole Permanent Magnet Machines for Automotive Applications

This article investigates the feasibility of interior consequent-pole permanent magnet (ICPM) machines with reduced rare-earth magnet consumption for automotive applications. A new ICPM machine with a double-layer V-shaped permanent magnet (PM) arrangement is proposed and compared with a commercial Nissan Leaf interior PM (IPM) machine. Their basic electromagnetic performances and rotor mechanical strength are evaluated by finite-element (FE) simulation. It shows that the proposed ICPM machine exhibits comparable torque capability, similar high-efficiency region, and significantly improved PM utilization ratio compared with traditional Nissan Leaf IPM case. Besides, to verify the universality of ICPM designs with reduced-rare-earth consumption, two typical ICPM machines with different magnet configurations (single- and double-layer V-shaped) and power levels (80 kW and 2 kW) are, respectively, investigated and compared with their corresponding traditional IPM counterparts. Finally, some tested results on an ICPM machine prototype with V-shaped magnets are carried out to validate the FE analysis.

Influence of Armature Reaction on Electromagnetic Performance and Pole Shaping Effect in Consequent Pole Pm Machines

Consequent pole permanent magnet (CPPM) machines can improve the ratio of average torque to PM volume, but suffer from more serious armature reactions. In this paper, the variations of electromagnetic performance of surface-mounted PM (SPM), conventional CPPM machines, and pole-shaped CPPM machines with armature reaction at currents up to 5 times overload are analyzed and compared. The flux densities, flux linkages, back EMFs, inductances, torque characteristics, and demagnetization withstand capabilities are analyzed by the finite element method (FEM) and frozen permeability method. It is validated that the third order harmonics in inductances for CPPM machines tend to be reduced as current rises since the saturation in iron pole is prone to reducing the saliency effect. But the armature reaction tends to result in the increase of torque ripple components for all the machines. It is also found that the overall torque ripple of asymmetric pole-shaped machine tends to increase significantly under overload conditions. On the contrary, the symmetrical pole-shaped machine can maintain a relatively stable torque ripple under overload conditions which is similar to the SPM counterpart. Additionally, due to the large armature reactions, CPPM machines suffer from weaker demagnetization withstand capabilities and weaker overload capabilities than their SPM counterparts. Four CPPM prototypes with and without pole shaping are tested to confirm the FEM analysis.

Vibration Reduction Design of Consequent Pole PM Machine by Symmetrizing Local and Global Magnetic Field

The consequent pole permanent magnet (CPM) machine is well known for its high magnet utilization ratio and poor vibration performance. This article focuses on electromagnetic vibration and its reduction design in CPM machines, and the conventional surface-mounted permanent magnet (SPM) machine is used as a benchmark. First, the asymmetrical magnetic field and unbalanced radial force of the CPM machine are investigated with emphasis. The slot-pole combination and force modulation effect are the two reasons for the unbalanced radial force generation. Afterward, two new designs to reduce the vibration caused by the unbalanced radial force are proposed, and the reduction principles are described in detail. Finally, the prototypes of the 12-slot/10-pole SPM and proposed CPM machines are manufactured. The tests are conducted to validate the theoretical analysis and proposed vibration reduction design.

Design and analysis of consequent pole permanent magnet synchronous motor with low torque ripple

AbstractPermanent magnet (PM) motor with consequent pole (CP) rotor can improve the PM utilisation ratio. However, one group of PMs with the same polarity is replaced by iron core, which deteriorates the electromagnetic performances of the motor, including asymmetric air‐gap magnetic field and larger torque ripple. To solve this problem, this study analyses the relationship between the torque ripple and the stator‐rotor magnetomotive force (MMF) harmonics, determines the harmonic orders causing the torque ripple of the CP PM (CPPM) motor, and proposes an unequal‐turn four‐layer winding structure which can eliminate the determining harmonics in the stator MMF. Furthermore, the electromagnetic performances of the CPPM motors with the proposed winding structure and traditional CPPM motors are investigated by the finite‐element analysis. It is verified that the CPPM motor with the proposed structure has better motor performances.

Optimal design of hybrid consequent-pole permanent magnet motor to reduce torque ripple

Compared with the surface-mounted permanent magnet (SPM) motors, the consequent-pole permanent magnet (CPM) motors can obtain the approximate output torque on the basis of saving 30% PM material. However, due to the special arrangement of the CPM motor, its torque ripple is large, which will affect the smooth operation of this kind of motor. Therefore, this paper proposes a hybrid consequent-pole permanent magnet (HCPM) motor with an auxiliary PM on one side of the iron pole, which can reduce the torque ripple and ensure smooth operation effectively. In order to make the performances of proposed motor better, the Taguchi method is used to optimize the proposed HCPM motor. Furthermore, the influence rule and the relative importance of each optimization variable on the optimization goal are obtained by the average value analysis and the variance analysis, respectively. According to the above analysis results, the optimized hybrid consequent-pole permanent magnet (OHCPM) motor is obtained. Finally, the performances of SPM motor, CPM motor, and OHCPM motor are compared to verify the validity of the proposed structure.

Complementarity analysis of consequent-pole bearingless flux reversal motor windings with different pitch matchings

First, a topology of a consequent-pole bearingless flux reversal (CPBFR) motor suitable for flywheel battery magnetic suspension support systems is proposed, and the specific forms of different winding pitches are analyzed. Then, the phenomenon of winding complementarity, which is unique to certain permanent magnet bearingless motors, is explained theoretically. The magnetic density distribution characteristics of the no-load air gap of the consequent-pole permanent magnet rotor are given, and the influence of different winding pitches on the no-load induced potential as well as the influence of different winding pitches on no-load induced potential harmonics are revealed. Finally, the working feasibility of the CPBFR motor is verified from the perspective of magnetic field distribution and the magnetic line of force.

Verifying the calculation approach for radial suspension force based on the airgap flux density for SPM, consequent‐pole, and bearingless AC homopolar motors

AbstractIn this paper, a calculation method is proposed for the radial suspension force of a bearingless motor with a surface‐mounted permanent magnet (SPM) rotor, a consequent‐pole permanent magnet (CPM) rotor, and a homopolar permanent rotor (HPM). The radial suspension forces are calculated mathematically and analytically using the airgap flux density. It was confirmed that the proposed radial force equations are practical to calculate the suspension force based on the airgap flux density. The CPM bearingless motor and bearingless AC HPM have salient pole rotors that interact with the 2‐pole Magnetomotive force (MMF) to generate 6‐ and 10‐pole components. As a result, the radial suspension force of the CPM bearingless motor is generated by 8‐ and 6‐pole, and 8‐ and 10‐pole magnetic flux, whereas the bearingless AC HPM produces the radial suspension force by DC and 2‐pole components. The shaft torque, the suspension force, and efficiency were also compared for SPM, CPM bearingless motors, and bearingless AC HPM. Consequently, the torque value of the CPM bearingless motor is quite close to SPM bearingless motor. Moreover, the suspension force of the CPM bearingless motor is quite close to bearingless AC HPM.

Mathematical Model Derivation and Experimental Verification of Novel Consequent-Pole Adjustable Speed PM Motor

This paper proposes a novel consequent-pole-type PM motor having a structure different from that of conventional consequent-pole-type PM motors. The proposed rotor structure is composed of a magnetic pole pair using a permanent magnet and an image-pole pair using a high permeability core. The windings facing the magnetic pole pair and the image-pole pair are connected in series in the rotor structure, the three-phase synchronous impedance is balanced, and the d-axis inductance is increased. Therefore, compared with the conventional consequent-pole type, the field weakening operation can be performed efficiently with a lower d-axis current. These advantages make it possible to expand the operating range during field weakening. Furthermore, to fix the driving control method of the proposed consequent-pole PM motor, the voltage equation of the proposed motor is derived and verified by analysis and experiment. In addition, the essential characteristics of the proposed motor were compared with that of a standard surface permanent magnet (SPM) motor and a conventional consequent-pole PM motor.

Suppression of Torque Ripple in a New Consequent-Pole Permanent Magnet Machine by Segmented Structure

A new consequent-pole permanent magnet (CPM) machine with segmented structure/unequal teeth (CPM-SU machine) is proposed in this article. The segmented structure is adopted to decrease the torque ripple. To improve the torque density, the structure of unequal teeth is used in this proposed machine. The five-phase winding located in the stator is composed of three fractional-slot concentrated windings (FSCWs), which are helpful to improve the fault-tolerant capability. Permanent magnets (PMs) are placed in the rotor. To decrease the PM cost, V-type PMs and iron cores are arranged with the sequence of S-iron-S-N-iron-N. The magnetic field generated by PMs is investigated, which is helpful to demonstrate the working mechanism of this proposed CPM-SU machine. To verify the superiority of the proposed CPM-SU machine, a conventional CPM machine with unsegmented structure/equal teeth (CPM-UE machine) is proposed. The electromagnetic properties of these two machines, including the electromagnetic torque, the cogging torque, and the back electromotive force (back EMF), are analyzed by the finite element (FE) method. The simulating results show that the CPM-SU machine can exhibit excellent performances, such as low torque ripple and high torque density.

Design optimization of consequent-pole PMSM by ON/OFF method and multi-objective evolutionary algorithms

Consequent-pole permanent magnet synchronous machines (CP-PMSMs) have attracted considerable interest because they can save considerable permanent magnets and provide acceptable torque performance. The aim of this paper is to discover the full design space potential of the CP-PMSM by optimizing the topology of iron poles. ON/OFF method is used to manage the design region, finding the trade-off relationship between the average torque and torque ripple is the optimization targets. To this end, the topology of iron poles will be optimized by redistributing the iron and air material over the design region. A set of Delaunay mesh-based evolutionary operators is proposed and formulated to apply multi-objective evolutionary algorithms (MOEAs) to the formulated problem. The resulting topologies and convergence of two MOEAs are presented, and the optimization results are discussed.