Conventional Permanent Magnet Motor Research Articles

Comparison of permanent magnet synchronous machine and permanent magnet flux‐modulated machine in direct drive considering number of rotor poles

AbstractDirect drive permanent magnet (PM) motors have become a very attractive choice for electric vehicles. Generally, PM motors are divided into PM synchronous motors (PMSMs) and PM flux‐modulated motors (PMFMMs). High torque density is the main requirement of direct drive motors, therefore, the structure of conventional PM motors is modified to boost the torque. Increasing the number of poles is a structural modification to achieve high torque density in PMSMs; however, a large number of poles affects motor characteristics such as power factor, flux weakening, losses, and efficiency. The other way to have high torque is to use PMFMMs, which have a high intrinsic torque density. This paper first compares the performance of PMSMs with different number of poles. Then the performance of PMFMMs and PMSMs are compared to show their differences. The performance of PMFMMs with different teeth modulators and magnetic gear ratios are predicted to show their effects upon its performance. The simulation results using finite elements method|finite element method (FEM) are presented, and finally, a PMFMM with 36 slots and 40 poles as case study is subjected to an experimental test and its results are compared with FEM.

Research on power density improvement for interior permanent magnet synchronous machine based on permanent magnet minimization

In order to improve the power density of the permanent-magnet synchronous machine and reduce the cost of effective materials, this paper investigated approaches of power-density improvement and discussed the influence of flux-weakening level and salient ratio parameters on the characteristics of torque and power for the interior permanent magnet synchronous machine (IPMSM) based on the permanent magnet (PM) minimisation. Firstly, the model of PM minimisation can be established based on the principle of equal area of stator and rotor magnetomotive force. According to the minimisation model, a formula is derived for calculation of structural parameters of the permanent magnets in the IPMSM. Besides, the relation among the interior multilayer permanent magnets is established. Then, comparing and analysing the extremum characteristics of the maximum torque output and maximum power output of the motor under different parameters, the regular influence on the IPMSM can be summarised between the parameter and the internal power factor angle. So, it can be proposed that the corresponding internal power factor angle with respect to the golden section ratio of the maximum torque output is around −35°. Finally, combined with the results of the finite element and analytical calculation, a 45 kW PM motor for electric vehicles was manufactured and tested in no-load, load and thermal experiment, respectively. The peak torque of the prototype lasted for 94 s and reached 2.3 times the rated torque. Compared with the conventional PM motor used for the electric vehicle, the power density was increased by more than 0.5 kW/kg which can verify the correctness of the theoretical analysis.

Torque Ripple Reduction for Permanent Magnet Motor using New Configuration for Concentrated Windings

This paper presents a new configuration for the concentrated windings of permanent magnet motors in order to reduce the torque ripple. There are limited choices for the concentrated windings in conventional permanent magnet motors when selecting the numbers of poles and slots, which results in winding factors for harmonics that cannot be zero and the corresponding torque ripple remains. Unlike conventional concentrated-winding motor, whose teeth are all wound with one coil, the proposed concentrated-winding motor has some teeth with multiple coils wound around. The number of turns for each coil can be optimized to reduce its winding factors for harmonics to nearly zero so that the corresponding torque ripple could be significantly reduced. Prototypes of the conventional and proposed motors were constructed, and the experimental results are compared. Simulation and experimental results confirm the torque reduction effect of the proposed concentrated-winding motor.

Torque Ripple Reduction for Permanent Magnet Motor using New Configuration for Concentrated Windings

This paper presents a new configuration for the concentrated windings of permanent magnet motors in order to reduce the torque ripple. There are limited choices for the concentrated windings in conventional permanent magnet motors when selecting the numbers of poles and slots, which results in winding factors for harmonics that cannot be zero and the corresponding torque ripple remains. Unlike conventional concentrated-winding motor, whose teeth are all wound with one coil, the proposed concentrated-winding motor has some teeth with multiple coils wound around. The number of turns for each coil can be optimized to reduce its winding factors for harmonics to nearly zero so that the corresponding torque ripple could be significantly reduced. Prototypes of the conventional and proposed motors were constructed, and the experimental results are compared. Simulation and experimental results confirm the torque reduction effect of the proposed concentrated-winding motor.

Design of Innovative Radial Flux Permanent Magnet Motor Alternatives With Non-Oriented and Grain-Oriented Electrical Steel for Servo Applications

Permanent magnet (PM) synchronous motors have become excellent alternatives for traditional induction and dc motors in numerous applications in recent years. Therefore, torque density and efficiency improvements in the development of PM synchronous motors have become a significant issue. In this study, various PM synchronous motor alternatives are proposed with both non-oriented (NO) and grain-oriented (GO) silicon steel material in the same stator in order to increase the power density and efficiency. A detailed performance comparison using 2-D/3-D finite element analysis (FEA) is completed and a feasible stator design is manufactured. The proposed design with GO material is also compared with a conventional PM motor with NO stator steel. As a result of the investigations, it is observed that the proposed motor with GO material in the stator has higher torque density and efficiency as opposed to the conventional PM motor.

Design and analysis of a new partitioned stator flux‐modulation motor for direct drive applications

In this study, in order to improve the torque density of the conventional permanent magnet (PM) motor, a flux-modulation (FM) motor employing the magnetic gear effect is proposed. However, the FM motor has space conflict in the finite stator area, which limits the further improvement of torque density. Therefore, a new partitioned stator flux-modulation (PSFM) motor with separated PM excitation and armature windings is artfully proposed. The main design parameters influence on the average electromagnetic torque in the proposed PSFM motor is investigated, together with the proposed FM motor. Furthermore, based on the optimal designs for the highest average electromagnetic torque in this study, the electromagnetic performances of the three motors, including back-electromotive force performances, torque characteristics and several other performances with respect to speed are analysed by finite-element method. Additionally in the PSFM motor, torque generation mechanism and the reduction method of torque ripple are theoretically analysed. Results show that the proposed PSFM motor exhibits 29.1% higher torque density than the FM motor and 87.6% higher than the conventional PM motor with reduced torque ripple and superior loss performance. Finally, the proposed PSFM motor is prototyped for verification.

Design and Analysis of Halbach Ironless Flywheel BLDC Motor/Generators

Halbach array-based permanent magnet (PM) brushless machines exhibit attractive features when compared with conventional PM brushless machines with normal segmented magnets, including the flux-concentration effect, essentially sinusoidal air-gap flux density due to PMs, and negligible cogging torque. However, as for a motor/generator used in flywheel, an external rotor composed of Halbach array and rotor back-iron is necessary to increase the inertia of flywheel system, which is different from the conventional external-rotor machines. In this paper, a Halbach array PM motor is studied compared with the radial magnet array. The relationship between the air-gap field distribution and the magnet array is discussed. Finally, the eddy current loss in PMs of the external-rotor ironless brushless dc motor is analyzed between the Halbach PM motor and the conventional PM motor.

A New Nine-Phase Permanent Magnet Synchronous Motor With Consequent Pole Rotor for High-Power Traction Applications

Although three-phase permanent magnet (PM) motors are quite common in industry, multi-phase PM motors are used in special applications where high power and redundancy are required. Multi-phase PM motors offer higher torque/power density than conventional three-phase PM motors. In this paper, a novel multi-phase consequent pole PM (CPPM) synchronous motor is proposed. The constant power-speed range of the proposed motor is quite wide as opposed to conventional PM motors. The design and the detailed finite-element analysis of the proposed nine-phase CPPM motor and performance comparison with a nine-phase surface mounted PM motor are completed to illustrate the benefits of the proposed motor.

Minimization of Eddy-Current Loss in a Permanent-Magnet Tubular Linear Motor

This paper presents a minimization of eddy-current loss (ECL) in permanent-magnet (PM) of three tubular linear PM motors (TLPMMs). Three-dimensional Finite-Element Analysis has been used for the simulations. The ECL component is usually not taken into consideration in conventional PM motors. In present technologies, ECL is generated inside magnets of PM motors, due to both the high conductivity of the rare-earth magnets and the harmonics of the slot. This loss can increase the temperature inside the magnets and that may deteriorate their magnetic properties and potential risk of thermal demagnetization. Therefore, in the translator, segmented magnets has been used, because the cancelation of the ECL with this technique is possible as illustrated by the FEA results. Meanwhile, for the stator core of the three proposed motors, soft magnetic composite (SMC) material, Somaloy 700 has been used for its low cost and approximately zero ECL.

A Novel Dual Three-Phase Permanent Magnet Synchronous Motor With Asymmetric Stator Winding

Although three-phase permanent magnet (PM) motors are dominant in industry, multi-phase PM synchronous motors present higher torque-to-weight ratios, better efficiency, and low torque ripple compared with three-phase conventional PM motors. These features make fault-tolerant multi-phase PM motors become attractive for safety-critical applications. In this paper, a novel PM multi-phase motor design with a dual three-phase asymmetric stator winding is proposed. The winding structure of the proposed motor is unconventional due to selected slot–pole combinations. Therefore, an asymmetric winding is needed. The detailed finite-element analysis of the proposed motor and a performance comparison between the conventional integer-slot (72-slot/12-pole motor) with symmetric winding and the unconventional fractional-slot (78-slot/12-pole motor) PM motors with asymmetric windings is performed to see the benefits of the proposed motor. It was shown that the novel unconventional multi-phase PM motor has excellent torque quality and slightly higher torque density levels.

Analysis of New Modular Linear Flux Reversal Permanent Magnet Motors

In the recent years, linear propulsion technology has been increasingly adopted in transportation, electromagnetic launch and aerospace applications. Compared with the conventional rotary-to-lin-early propulsion, the linear propulsion can offers many advantages, such as high efficiency, reduced maintenance cost, vibration and noise [1]-[4]. Among various kinds of linear motors for linear propulsion system, the linear permanent magnet (PM) motors has gained more and more attention due to the merits of high power density and efficiency. However, since the PMs or windings are set on the long stator, the conventional PM motors suffers from high cost for the long stroke applications such as rail transit. The linear flux reversal permanent magnet (FRPM) motor combining PMs and windings on the mover has been regarded as a potential solution, but its fault tolerance is poor [4]-[6]. In [4], the fault tolerance of linear FRPM motor was improved by utilizing a modular mover structure. However, it suffers from the low PM magnetic field utilization and force density due to its homopolar flux linkage. Furthermore, its force ripple and cogging force is very large, which deteriorate the force performance. In order to improve these problems, a new linear FRPM motor with modular mover will be proposed in this paper, which not only retains the advantages of the existing modular linear FRPM motor such as fault tolerance and reduced PM consuming, but also significantly enhances its force density and reduces its force ripple.

Research on ALA+SPM Rotor Synchronous Motor Direct Torque Control

This paper compares the electromagnet torque characteristics of ALA+PM rotor synchronous motor with the conventional permanent magnet motor, the former holds on linearity relationship with the increase of the stator flux linkage, but the later needs restrict condition. The direct electromagnet torque control is the best control method for ALA+PM rotor synchronous motor, but the stator current can increase if the stator flux linkage is bigger or smaller than magnet flux linkage, the maximum torque current percent ampere control method is used to overcome the disadvantage.

INTERIOR PERMANENT MAGNET MOTOR HAVING SEVERAL IMPROVED FEATURES

ABSTRACT The no-load airgap flux density distribution of most conventional permanent magnet motors is square in shape. The rotor configurations having interior magnets employed in these machines also lead to vastly different saliencies along the d- and q-axes giving a quadrature axis inductance larger than the direct axis inductance. A modified rotor configuration is presented that produces a near sinusoidal airgap flux density distribution which is achieved by shaping the rotor airgap profile while keeping the interior magnets rectangular in shape. As a result of this shaping the quadrature axis inductance is reduced significantly while there is almost no change in the direct axis inductance. It is also shown that the new rotor configuration leads to significantly reduced cogging torque and less saturation along the q-axis which assists in maintaining a linear torque versus current relationship in field oriented control employing the quadrature axis current. Airgap flux density levels, inductances and static torque characteristics obtained using the finite element simulation work are presented comparing them with those for a uniform airgap machine. There has been good agreement between the experimental and simulation results. The operational advantages gained by the improvements made are also briefly discussed.