Outer Stator Research Articles

Performance improvement of asymmetrical-pole partitioned stator permanent magnet generator by optimizing stator teeth number

The partitioned stator doubly salient permanent magnet generator (PS-DSPG) with asymmetrical-pole configuration has been widely applied for producing electrical power due to their high reliability, high flux linkage and high electromagnetic force (EMF). Therefore, we aim to improve the performance of this generator an asymmetrical-pole structure technique applied to outer stator pole. The phase flux linkage and phase EMF were characterized by finite element method. It was verified that the flux linkage and EMF were increased when increasing the number of outer stator. Especially, the 30/8/14-pole (outer stator/rotor/PM-pole) of PS-DSPG structure with asymmetrical-pole technique produced high symmetric EMF waveform. the arc variation of rotor iron piece of all proposed structures was investigated. It was found that the 30/8/14-pole of the proposed asymmetrical-pole PS-DSPG structure provides EMF about 61.29% higher than the conventional structure at expanded rotor arc of 140%. Hence, the 30/8/14-pole asymmetrical-pole PS-DSPG structure can be utilized for electrical generation in low-speed applications.

Comparative Study of Partitioned Stator Memory Machines With Series and Parallel Hybrid PM Configurations

In this paper, the partitioned stator (PS) structure is extended to variable-flux memory machines, forming two newly emerged PS switched-flux memory machines (PS-SFMMs) with series and parallel hybrid magnet configurations. From the perspective of geometry, both two PS-SFMMs share identical outer stator and rotor segments, while two different types of permanent magnet (PM) arrangements are employed in the inner stationary part. Thus, the developed machines can inherent the geometric separation of the armature winding and PM excitations from the PS design, thus achieving acceptable torque capability, and excellent air-gap flux control. A comparative study between PS-SFMMs with series and parallel structures is established. First, the topologies and operating principle are introduced, respectively. In addition, the design tradeoffs and PM sizing of the two PS machines are revealed and optimized with a simplified magnetic circuit model. Then, the electromagnetic characteristics of PS-SFMMs with different magnetic circuits are investigated and compared with the finite-element (FE) method. The FE results are validated by the experiments on a parallel prototype.

Influences of Stator Teeth Number on PM Coupling Levels of Co-Axial Dual-Mechanical-Port Flux-Switching PM Machines

In this paper, the influence of stator teeth number on permanent magnet (PM) field couplings of co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machines for fuel-based extended-range electric vehicles is investigated. First, the relationships between the inner and outer stator teeth numbers are analytically evaluated. Second, four typical structures, including 5/6-12/22, 10/12-12/22, 5/6-18/42, and 10/12-18/42, of CADMP-FSPM machines are analyzed, and three key stator teeth types, namely, series, parallel, and independent teeth, are defined. Third, the PM field coupling levels of four structures, featured by PM field distributions and air-gap flux densities, are compared with stator teeth matchings. The results indicate that the 10/12-12/22 structure exhibits the lowest PM field coupling and the prior open-circuit performance. Furthermore, the PM field coupling effects on the inner and outer air-gap flux densities are analyzed. Finally, a prototyped 10/12-12/22 CADMP-FSPM machine is designed, optimized, and manufactured, and the experimental results verify that the PM field coupling level of the prototype is negligible, which agrees well with the finite-element predictions and the proposed matching criteria for the selection of the inner and outer stator teeth numbers of CADMP-FSPM machines.

Electromagnetic Analysis and Optimization for a Dual-Rotor Switched Reluctance Machine

A dual-rotor switched reluctance motor is proposed in this paper. The structure and working principle of the motor are introduced in detail. The structural parameters have great influence on the performance of the motor, so sensitivity analysis of several important structural parameters to the output torque is carried out based on the two-dimensional finite element method, which improves the average torque of the rotor in the outer air gap. Additionally, the performance of the motor with various pole distributions is analyzed and compared. The results show that when the magnetic polarity distribution of the outer stator is NSNSNSNSNSNS and the magnetic polarity distribution of the inner rotor is NSNSNS, the motor has the best performance. The torque of the motor is compared with that of the traditional single-rotor switched reluctance motor. It shows that the performance of the motor proposed in this paper is better.

Squirrel Cage Induction Motor Design and the Effect of Specific Magnetic and Electrical Loading Coefficient

3-phase induction motors are widely used in industrial applications such as pumps, blowers, compressors, conveyors, etc. In addition, single-phase motors also have domestic use. For this reason, the design of the induction motor is of great importance. During the design, according to the parameters given as input, there are many situations that are contradictory to each other in order to achieve the goal. For example, if high efficiency is required, the motor size and the price will increase, and if lower price is required, other performance characteristics should be ignored. In the practical design of an induction motor, the designer has to comply with a number of constraints because of the large number of input variables. For this reason manual calculation becomes a very long and difficult process. To overcome this tiresome process, it is necessary to create a computer aided program or simulation model to determine the induction motor design parameters. In induction motor design, many parameters directly affect motor performance. Therefore, the selection of these parameters is of great importance. The C0 coefficient, which takes place in the first steps of the design process, also has a great influence on the motor design. In this paper, a program for optimizing design of 3-phase induction motors written in MATLAB is presented. The structure of the program is modular and therefore can be modified for the various requirements of the induction motor design. C0 constant (output coefficient), one of the design parameters, also varies with some other parameters. The most important ones are the specific electrical loading coefficient (A1) and the specific magnetic loading coefficient (Bav), making dramatic effect on the output coefficient. The effect of the variation of the C0 constant on the performance of the induction motor was investigated in the study. Stator inner and outer diameter, stack length, stator and rotor slot parameters, equivalent circuit parameters, losses and efficiency was obtained according to the change of Bav and A1 values. The obtained results are given and interpreted in tables and graphs.

Sensorless control on a dual-fed flux modulated electric motor

This paper proposes the operation principle and a new flux estimation method for sensorless control strategy for the dual-fed flux modulated electric motor (DFFM). The DFFM is designed based on the flux modulation theory, it includes two stator windings and one rotor which simplify the mechanical structure. The rotor has only modulation iron and no permanent magnets on it, so there is no cogging torque problem in this motor. With adjustment of the outer and inner stator flux rotating frequency and amplitude, different rotation speed and torque of the sandwiched rotor can be gained for the DFFM. Furthermore, an improved flux estimation based sensorless control strategy is performed on the proposed machine to fit the two winding set control situation. The startup and performance of the proposed control strategy is verified by the simulation and experiments.

Analysis of a New Dual-Stator Vernier Machine With Hybrid Magnet Flux-Reversal Arrangement

This paper proposes a new hybrid magnet (HM) dual-stator vernier machine (DSVM) with flux-reversal (FR) magnet arrangement, in which NdFeB and ferrite magnets are reversely mounted on tooth tips of outer and inner stators, respectively. The hybrid dual excitation topology enhances the magnetic fields of inner and outer air-gaps, which are modulated by the rotor composed of iron poles. The proposed topology, operating principle, and design consideration are described. The merits of the proposed HM-FRDSVM are verified when compared to the same FRDSVMs with dual NdFeB magnet excitation and with dual ferrite magnet excitation and the conventional dual stator synchronous permanent magnet machine. The two-dimensional finite element analysis results show that the proposed machine has high torque cost performance with low torque ripple and low cogging torque that are desirable for large telescope drive application.

Analytical Model of a Spoke-Type Permanent Magnet Synchronous In-Wheel Motor With Trapezoid Magnet Accounting for Tooth Saturation

This paper presents an analytical model for the prediction of the performance in a spoke-type permanent magnet synchronous in-wheel motor with a trapezoid magnet accounting for tooth saturation. The impact of magnet shape on modeling is considered. To match the standard boundary conditions, the trapezoid magnet is simplified to sector magnets. According to the invariance principle of the magnetic field created by the magnet, the dimension of the sector magnet is calculated with a lumped magnetic circuit model. Then, the motor is divided into six subdomains, i.e., shaft, inner sector magnet, outer sector magnet, rotor slot, air-gap, and stator slot. Based on the boundary conditions, the magnetic field, back electromotive force, and torque are obtained by solving Poisson's and Laplace's equations. The effect of tooth saturation is considered. The finite-element method and experiments are employed to validate the accuracy of the analytical model. In addition, the proposed method can also be used to evaluate the performance of the spoke-type motor with any irregular magnet.

Tubular unified magnetic‐field flux‐switching PMLM for free‐piston energy converter

A tubular flux-switching permanent-magnet linear machine (PMLM), which features unified magnetic field between the mover and two stators, is investigated for free-piston energy converter. The topology evolution, topology, operating principle and design considerations of the machine are thoroughly analysed. With the sinusoidal speed characteristic of free-piston Stirling engine considered, a tubular unified magnetic-field flux-switching PMLM is designed by finite-element analysis. Several main structural parameters, which include the outer and inner radius of the mover, the mover tooth width, the magnet thickness, the tooth widths of both the outer and inner stators and the widths of both the outer and inner stator yokes are studied to achieve high-force and mass-power density. Finally, the proposed machine is compared with two typical flux-switching PMLMs. The comparison results show that the unified magnetic-field flux-switching PMLM is suitable for applications which require high-power density, light mover structure and fast dynamic.

Study on Different Connection Modes of Dual-Stator Brushless Doubly-Fed Machine Based on Field-Circuit Method

The different winding connection modes of dual-stator brushless doubly-fed machine (DSBDFM) are investigated to ensure the electromagnetic characteristics consistency of outer and inner stator. The electromagnetic characteristics consistency is not only required that the electromotive force (EMF) amplitude and phase match the requirements of outer and inner stator winding connection mode, but also the number of parallel branches of winding should be considered to avoid the circular current and phase difference. This paper proposes a method for the number of parallel branches of winding, which is helpful to determine the number of parallel branches of two sets of winding with different pole pairs number in stator slots and ensure the EMF amplitude and phase of per branch winding. The field-circuit method (FCM) is used to analyze the different connection modes of DSBDFM, such as series, parallel, series and parallel. The finite element method was confirmed agreement with the FCM, indicating the validity and rationality of FCM.

Analysis of Performance Improvement and Acoustic Property of Giromill Vertical Wind Turbine with Outer Stators

Analysis of Performance Improvement and Acoustic Property of Giromill Vertical Wind Turbine with Outer Stators

Novel Dual-Stator Machines With Biased Permanent Magnet Excitation

This paper proposes high-torque-density dual-stator permanent magnet machines with biased permanent magnet (PM) excitation in the inner stator. The developed machine can be geometrically considered as an outer-rotor stator PM machine plus a separate outer stator similar to the conventional fractional-slot machines. Consequently, the proposed designs feature two different stator structures. Meanwhile, two sets of armature windings are employed to improve the space utilization ratio and torque density. The machine topologies and operating principles are first described. In addition, the analytical models of the machine are introduced, which are utilized to optimize the stator/rotor pole combination as well as the power splitting ratio between two stators. This design optimization is performed in order to maximize the torque capability with the constraint of copper loss. The electromagnetic characteristics of the proposed machine with different inner stator structures are evaluated and compared by the finite-element (FE) method. Finally, an optimized dual-stator biased PM machines prototype is manufactured and tested to verify the FE analyses.

Electromagnetic Flux Analysis of Ds Hesfm for Directly Driven Actuator Used in Aircraft Applications

This paper presents the electromagnetic flux analysis of dual stator hybrid excitation switched flux machines (DS HESFM) using segmental rotor for the directly driven electromechanical actuator aimed to use in aerospace applications. The advantage of designing a machine with directly driven system is to eliminate the intermediate gear box system with having minor component count and reduced jamming possibility. The proposed design of DS hybrid excitation with high torque density is investigated in this paper as a potential solution for aircraft applications. The key intentions of the design are high level of actuator integration to reduce the overall weight and volume and fault tolerance ability. The proposed design of DS HESFSM has simple structure, which consist of only six field excitation coils (FECs) housed in outer stator along with six armature coils (ACs) whereas, six permanent magnets (PMs) are positioned in the inner stator. Moreover, DS HESFM structure is analyzed at open circuit and short circuit conditions conditions by means of “commercial 2D FEA package, JMAG-designer ver. 14.0,” released by JSOL Corporation.

Analysis of coupling between two sub‐machines in co‐axis dual‐mechanical‐port flux‐switching PM machine for fuel‐based extended range electric vehicles

The permanent magnet (PM) field coupling between inner and outer machines of co-axis dual-mechanical-port flux-switching PM (CADMP-FSPM) machines is investigated. Firstly, the relationships between the inner and outer stator teeth are analytically evaluated, with three key stator teeth types defined, i.e. series, parallel, and independent teeth. Secondly, the negative effects of PM field coupling, including high even-order electromotive force (EMF) harmonics, three-phase EMFs asymmetry and DC bias component in flux-linkages, are investigated and verified by two CADMP-FSPM machines, namely, 5/6-12/22, and 5/6-18/42 structures. It is found that for avoiding the negative effects of PM field coupling, all inner and outer stator teeth types should be the same, thus, a 10/12-12/22 structure CADMP-FSPM machine is introduced for analysis. Thirdly, the performance of the 10/12-12/22, 5/6-12/22, and 5/6-18/42 structures, featured by PM field distributions, d-axis flux-linkage ripples, cogging torques, electromagnetic torques, losses and efficiencies, are comparatively analysed by finite element (FE) analysis. The results indicate that the 10/12-12/22 structure exhibits the lowest PM field coupling level and the best performance. Moreover, the 10/12-12/22 structure can avoid all the negative effects of PM field couplings. A prototyped 10/12-12/22 CADMP-FSPM machine is built and tested to verify the FE predicted results.

Vibroacoustic Prediction of a High-Temperature Superconducting Field-Modulation Double-Stator Machine with Stationary Seal

This paper predicted the vibroacoustic regularity of a high temperature superconducting (HTS) field-modulation double-stator (HTS-FMDS) machine with stationary seal for low-speed and direct-drive applications. The originality of this paper lies in that the spatial order and angular velocity of electromagnetic-force density of the HTS-FMDS machine were derived by using the analytical method. Moreover, the validity of the analytical solutions was verified by the finite element analysis (FEA) results. Then, the modal shapes and frequencies of the outer stator were obtained by using multiphysics coupling simulation. By transferring the electromagnetic force to the stator structural model, the regularity of electromagnetic vibration and noise of the HTS-FMDS machine were revealed.

Electromagnetic Characteristics Analysis of a High-Temperature Superconducting Field-Modulation Double-Stator Machine with Stationary Seal

This paper has proposed a high temperature superconducting (HTS) field-modulation double-stator (HTS-FMDS) machine with a stationary seal for low-speed and direct-drive applications. The originality of this paper lies in the HTS field-excitation windings, which were fed with a direct current in order to offer strong field excitation, were placed in the inner stator, while the armature windings were installed in the outer stator so that the stationary seal of the cryogenic cooling system could be achieved. Moreover, a ferromagnetic ring was mounted on the top of each HTS coil to prevent the quench of the HTS wires resulting from the armature-reaction magnetic-field. By using finite-element analysis (FEA), the influence of the armature-reaction magnetic-field on the critical current and the electromagnetic properties were carried out so as to verify the validity of the proposed machine.

Numerical investigation of pump performance and internal characteristics in ALIP with different winding schemes

Annular linear induction pump (ALIP) is considered as an ideal type of coolant pump in liquid metal cooled reactors. However, the low pump efficiency and the flow instability have yet been solved, especially for large-scale pump design. In this work, a two-dimensionally symmetrical ALIP model is de veloped and both single-sided (SS) and double-sided (DS) windings in stators are simulated in the designed ALIP model. The pump performance characteristics (H-Q curve) are obtained by calculating the differential pressure between inlet and outlet at varying flow rate conditions. The simulated results are validated with the previously published experiment. The results show that the differential pressure of the DS-type pumps is slightly lower than that of SS pump with the same input energy while the radial velocity profile in the channel of the DS pumps with the winding number of outer stator twice that of inner stator shows the best uniform velocity distribution. By peeking into the Lorentz force and induced magnetic field, the DS pump with equal winding numbers at inner and outer stators actually deteriorates the induced magnetic field, resulting in a highly non-uniform Lorentz force in the channel radial direction, particularly at high flow rate. The results demonstrate the importance of finding an appropriate ratio of winding numbers in the DS-type pump design in order to improve the pump performance.

Electromagnetic Design and Losses Analysis of a High-Speed Permanent Magnet Synchronous Motor with Toroidal Windings for Pulsed Alternator

The configuration of conventional high-speed Permanent Magnet Synchronous Motors (PMSMs) is usually long and thin, with overlong axial end winding lengths, which is not suitable for those applications that place severe restrictions on the axial length, such as pulsed alternators. This paper first studied the key design aspects of a flat-structure high-speed PMSM. The toroidal-windings, low-conductivity material of the retaining sleeve, large airgap and segmentation of magnets were studied to reduce the axial length of the motor. The division of the stator and the employment of a non-magnetic outer stator were used to improve overall performance. Then the losses of the prototype were calculated and the factors having an influence on the losses were also investigated, after which, their effects on the total loss were evaluated. The total loss could be effectively reduced by the decrease of strand number of conductors and the division of stator, while only being slightly reduced by epoxy resin pole fillers. Metal-stack pole fillers have the same effect on the reduction of rotor loss as epoxy resin, while maintaining the good thermal-conductivity of metal. In addition, the influence of the carrier frequency of the inverter on the losses was analyzed, and it was found that high carrier frequency was helpful to reduce rotor losses. Finally, a small-scale prototype was manufactured and the experimental results were provided.

Design Optimization of a Novel Scale-Down Hybrid-Excited Dual Permanent Magnet Generator for Direct-Drive Wind Power Application

This paper presents a novel scale-down hybrid-excited dual permanent magnet (PM) generator for direct-drive wind power application. Two sets of consequent-pole PMs are used in the proposed design, with one on the outer stator and the other on the middle rotor. PMs are separated by iron poles one by one, to form the magnet-iron sequences, which can provide PM excitation and flux modulating simultaneously. Since both the outer stator and middle rotor have flux modulating effect, bi-directional flux modulating can be achieved. Besides the fundamental field components, some other major field harmonics are also synchronous due to the bi-directional flux modulating effect, and these harmonics can contribute to the electromagnetic generation. Therefore, the proposed machine can achieve high torque density and suitable for direct-drive applications. Field windings are employed on the outer stator, so the air-gap field can be easily regulated by controlling the dc current. Hence, the proposed generator can maintain constant output voltage when the wind speed varies. Finite-element method coupled with genetic algorithm is used to optimize a scale-down design of the proposed generator, and its electromagnetic performances are studied in detail.

Design and Analysis of In-Wheel Double Stator Slotted Rotor BLDC Motor for Electric Bicycle Application

<p>This paper discusses about design and analysis of double stator slotted rotor (DSSR) BLDC motor for electric bicycle application. Usually single stator (SS) BLDC motor is used in an electric bicycle. This type of motor has low performance and need to be charged regularly. The objective of this research is to design and analysis DSSR motor that have high torque. At starts, design specification for the electric bicycle is calculated. Next, design process for DSSR is carried out by using the desired parameter. Lastly, analysis for double stator slotted rotor is simulated using FEM. Result for average back emf, average inductance, inner stator flux density, outer stator flux density, average torque and estimate torque constant is obtained. Result for average torque from FEM archieve the requirement of motor torque for DSSR design where the maximum average torque is 16.2 Nm. This research will give benefit to mankind and society in term of environment protection and energy consumption.</p>