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Comparative Study of Hybrid PM Memory Machines Having Single- and Dual-Stator Configurations
Abstract
In this paper, the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations. Two types of permanent magnets (PMs), i.e., NdFeB and low coercive force (LCF) PMs, are located in the stationary part. Thus, the developed machines can achieve easy online PM magnetization control, excellent air-gap flux control, and acceptable torque capability. In order to address the issue about the limited stator space encompassing dual PMs and magnetizing coils in the SS-SFMM, a DS design is further developed, where all excitations are placed on a separate inner stator to improve the torque density. A comparative study between the SFMMs with SS and DS structures is established. The investigated machine topologies and operating principle are described first based on a "U"-shaped hybrid PM arrangement, and the PM sizing of the DS machine is optimized with a simplified magnetic circuit model. In addition, the electromagnetic characteristics of the SFMMs with SS and DS structures are investigated and compared by finite-element (FE) method. The FE results are validated by the experiments on two fabricated prototypes. IEEE
... Variable flux memory machine (VFMM) has been considered as an effective solution to resolve the conflict between high torque at low-speed conditions and constant power maintaining capability at high-speed conditions in conventional PM machines [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The low coercive force (LCF) magnet in VFMM makes air-gap flux regulation convenient by applying a temporary magnetizing or demagnetizing current pulse [3,4]. ...
... Meanwhile, there is a negligible associated excitation loss during the flux regulation, which achieves excellent FW capability and high efficiency over a wide speed range. Nonetheless, due to the low torque density of VFMMs having the LCF magnet as the only magnetomotive force (MMF) source, some hybrid PM VFMMs were presented and extensively investigated [5][6][7][8][9][10][11][12][13][14][15]. ...
... In order to qualitatively reflect the possible effects of the PM arrangements on the flux adjusting range, a simplified equivalent magnetic circuit of PHMMM is established as shown in Figure 5. The peak air-gap fluxes at the flux-enhanced/weakened states are expressed as [7]. ...
This paper presents a comparative analysis of two parallel hybrid magnet memory machines (PHMMMs) with different permanent magnet (PM) arrangements. The proposed machines are both geometrically characterized by a parallel U-shaped hybrid PM configuration and several q-axis magnetic barriers. The configurations and operating principles of the investigated machines are introduced firstly. The effect of magnet arrangements on the performance of the proposed machines is then evaluated with a simplified magnetic circuit model. Furthermore, the electromagnetic characteristics of the proposed machines are investigated and compared by the finite-element method (FEM). The experiments on one prototype are carried out to validate the FEM results.
... Permanent-magnet (PM) synchronous machines (PMSMs) are widely used in servo systems, traction fields and household applications owing to their high power density and high efficiency. 1 However, the unadjustable air-gap flux of the conventional rare-earth PM machine leads to limited constant-power speed range (CPSR), and the efficiency is lower at high speed region which results from the inescapable flux-weakening current. 2 To improve this situation, the concept of variable-flux PMSM (VF-PMSM) is proposed. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Since the low coercive-force (LCF) magnet is utilized in the VF-PMSM, the air-gap flux can be changed by applying d-axis current pulse to re/demagnetize the LCF magnet. The magnetization states (MSs) of the LCF magnet can be 'memorized' depending on the amplitude of the current pulse, and the copper loss during the re/demagnetization process is negligible. ...
... 5,6 Due to the low torque density of VF-PMSMs where the LCF magnet are employed only, hybrid-PM variable-flux machines (HPM-VFMs) are proposed to combine the high torque density of the rare-earth PM machine and flux adjustability of the VF-PMSM. [10][11][12][13][14][15][16] Generally, HPM-VFMs are classified into parallel and series configuration according to the arrangement of the low and high coercive-force magnets. For parallel-configuration HPM-VFMs, wide range of flux regulation capability can be realized, because the magnetization orientation of LCF magnets can be changed in two directions. ...
... For parallel-configuration HPM-VFMs, wide range of flux regulation capability can be realized, because the magnetization orientation of LCF magnets can be changed in two directions. [10][11][12] However, the working points of LCF magnets tend to be easily affected by q-axis armature reaction and the high coerciveforce (HCF) magnet, so the torque density of parallel-configuration machines is reduced. [13][14][15][16] Owing to the enhancement of the HCF magnet, the LCF magnet in series-configuration HPM-VFMs can resist the demagnetization effect from the load armature reaction. ...
Aiming at extending the operating speed range and increasing the machine efficiency, three series-configuration hybrid-permanent-magnet variable-flux machines (HPM-VFMs) with both low and high coercive-force magnets are proposed. The magnetization characteristics of the machine with different dimensions of the high coercive-force (HCF) magnet are investigated. Then, in order to improve the contribution rate of the HCF magnet, two improved topologies are presented. The electromagnetic characteristics of the two proposed machines, including back electromotive force (EMF), maximum torque characteristics, magnetization state (MS) variation range and magnetic field distribution, are comprehensively analyzed and compared. The influence of different types of windings on the performance of the machine is also investigated. Finally, the torque-speed curves of the machine under different MSs are given by finite element method (FEM). The results show that the HPM-VFM can operate over a wide-speed range with high efficiency.
... under on-load operation. On the other hand, all the stator PM machines, e.g., doubly salient [15][16][17], and switched flux (SF) [18][19][20][21][22][23] topologies can be converted into DC-magnetized type MMs. Compared with conventional stator PM machines, DC magnetizing coils are added in the stator PM MMs to generate a transient current pulse to change the intensity of magnetization level of the LCF PM materials. ...
... The design possibilities of various PM configurations for the PS-HMMMs are investigated in reference [21], which shows the spoke-type PM design is preferable for the torque enhancement. In reference [22], the performance comparison of SF-HMMMs with single-or dual-stator structures is conducted, which confirms the benefits of the PS design in terms of torque improvement and wider flux regulation range. Triple magnets are employed in reference [23] to further improve the unintentional demagnetization withstand capability. ...
... Triple magnets are employed in reference [23] to further improve the unintentional demagnetization withstand capability. In reference [22], comparison between the PS-HMMMs and the commercialized EV machine has been made regarding the back-EMFs (electromotive force), torque characteristics, and efficiency maps. It shows that the PS-HMMMs have comparable torque density, better efficiency maps, and higher torque at light load. ...
This paper presents general design considerations of a partitioned stator switched flux hybrid magnet memory machine (PS-SF-HMMM). The armature windings and permanent magnets (PMs) are placed on two separate stators, respectively, in the PS-SF-HMMM, and thus both high torque density and wide flux regulation capability can be obtained. The topology and working principle of the machine are introduced briefly first, and then different magnet arrangements and stator/rotor pole combinations are investigated. In addition, various design parameters are optimized based on finite element (FE) methods. Finally, a prototype is fabricated to experimentally validate the FE results.
... First, for the parallel case, the air-gap fluxes Φ pδ+ and Φ pδ− at 274 the flux-enhanced and flux-weakened states can be formulated 275 [26]. ...
... where H c1 and H c2 are the coercive forces of LCF and NdFeB 277 PMs, respectively; h m 1 and h m 2 are the thicknesses of LCF and 278 NdFeB PMs, respectively; R g is the air-gap magnetic reluctance. 279 For the series type, the corresponding peak open-circuit 280 air-gap fluxes Φ sδ + and Φ sδ − at the flux-enhanced and flux-281 weakened states can be analogously expressed as [21], [26] 282 ...
... It is ap-408 parent that both the HMC and series designs show a comparable 409 saliency ratio; whereas, the negligible reluctance torque can be 410 observed in the parallel case, which is mainly due to the sig-411 nificant cross-coupling demagnetization effect occurring in the 412 LCF PMs [16]. In addition, the steady-state torque waveforms 413 of the three VFMMs under-rated current (I rms = 5.3 A, "rms" 414 denotes root-mean-square value) are shown in Fig. 13 coverage process relatively time-consuming in FE software due 424 to the nonlinear hysteresis property [26]. ...
This paper proposes a novel hybrid-magnetic-circuit variable flux memory machine (HMC-VFMM) by combining series and parallel hybrid magnet structures. Thus, the synergies of wide flux regulation range in parallel type and excellent on-load demagnetization withstand capability in series type can be simultaneously obtained with the proposed HMC design. Meanwhile, two sets of the permanent magnets (PMs) with high coercive force (HCF) and low coercive force (LCF), i.e. NdFeB and AlNiCo PMs, are employed to achieve high torque density and energy-efficient magnetization state (MS) adjustment. The topologies and tradeoffs of traditional parallel and series VFMMs are addressed first. In addition, the structure evolution, features and operating principle of the proposed HMC-VFMM are described, respectively. A simplified equivalent magnetic circuit is modelled to reveal the performance improvement of the machine. Then, the design improvements with q-axis barriers are presented to elevate the LCF PM working point for preventing the on-load demagnetizing effect, while maintaining the torque capability. The electromagnetic characteristics of the HMC design are investigated and compared with the parallel/series counterparts. Finally, the experiments have been carried out to validate the finite element (FE) analyses.
... Nevertheless, due to the crowded stator issue in single-stator dc-magnetized MMs [9]- [17], the torque density is inevitably compromised. In order to alleviate this issue, a partitioned stator switched-flux MM (PS-SFMM) is developed [15]- [17]. The armature windings and PMs are separately located on two stators, respectively. ...
... Hence, high torque density and energy-efficient flux control capability can be simultaneously realized. However, the previous studies mainly focus on the new topology development [15], [16] and performance analysis [17] in individual cases. Nonetheless, the feasibility of possible magnetic circuits and the corresponding characteristic investigation for the PS-SFMMs remains unreported. ...
... The simplified magnetic circuits of the spoke-type PS-SFMMs with series and parallel PM arrangements are portrayed in Figs. 4 and 5, which neglect the magnetic reluctances of iron parts. First, for the parallel case, the air-gap fluxes δ+ and δ − at the flux-enhanced and flux-weakened states can be analytically formulated for the further optimization [15] ...
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.
... For the rotor-PM machines [7]- [12], the thermal management and protection issues associated with the PMs tend to be problematic issues for the DS machine with cantilever cupped rotor. On the other hand, the stator-PM DS [13]- [19] machine can well facilitate the PM heat dissipation, but also have simple and robust rotor which is preferable for high-speed critical-safety operation. ...
... The switched flux (SF) [13]- [19] and doubly salient [20] designs were extended to the DS structures in potential context of automotive traction applications. In general, the stator-PM DS machines can be divided into yoke [13]- [14] and yokeless [15]- [19] types based on the rotor structure. ...
... The switched flux (SF) [13]- [19] and doubly salient [20] designs were extended to the DS structures in potential context of automotive traction applications. In general, the stator-PM DS machines can be divided into yoke [13]- [14] and yokeless [15]- [19] types based on the rotor structure. The former type can be considered as a combination of two identical singlestator SFPM machines [14]. ...
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 DS-BPMM prototype is manufactured and tested to verify the FE analyses.
... The flux-modulated concept is extended to DC-magnetized MM to combine high torque density and wide flux regulation capability [39]. Very recently, various switched flux MMs (SFMMs) [40]- [43] were presented to resolve the demerits of relatively complicated decoupling current control in AC-magnetized ones, and large torque ripple issue in DSMMs. ...
... On the other hand, for high-speed region, the LCF PMs are reversely demagnetized to short-circuit and weaken the NdFeB PM fields, and hence the CPSR can be effectively extended within the limitation of the inverter power rating. The variable flux principle of the proposed DSPM-MM can be characterized by a simplified illustration of the parallelogram hysteresis model of LCF PMs as shown in Fig. 4 [32]- [40]. It can be seen that the coercive force of LCF PM is much lower than that of NdFeB. ...
... Hysteresis curves of hybrid PM materials[32]-[40]. ...
Memory machine (MM) equipped with hybrid permanent magnets (PMs), i.e., NdFeB and low coercive force (LCF) PMs, exhibits acceptable torque capability at low speeds and high efficiency at high speeds. Previous literatures have addressed that the constant power speed range (CPSR) of MMs can be further extended by online PM flux control, and the requirement of flux-weakening (FW) inverter current can be reduced as well. Nevertheless, how to coordinate the d-axis vector FW and PM magnetization control over a whole operating range in a reasonable manner remains unreported. Therefore, this paper proposes and implements a stepwise magnetization control strategy on a DC-magnetized memory machine based on the operating characteristics under various PM magnetization states and speed ranges. The configuration, principle and mathematical model of the investigated machine are introduced first. Then, the proposed control strategy is established by dividing the operating envelop into several FW regions, and an appropriate FW control scheme is utilized at each stage. It demonstrates that the CPSR can be effectively extended by simply applying the demagnetizing current pulses in several steps. This simplifies the control efforts considerably without resorting to continuous PM flux control and frequent actions of the switching devices. The effectiveness of the proposed control strategy is verified by experimental results. IEEE
... Very recently, in order to achieve an energy-efficient flux adjustment, the concept of memory machine (MM) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] has been extended to SFPM machines, forming a new type of switched flux hybrid magnet MM (SF-HMMM) [23][24][25]. The auxiliary DC magnetizing coils are employed to generate a current pulse, thereby facilitating the online magnetization, since transient remagnetizing and demagnetizing current pulses are applied to adjust the air-gap flux, which simply requires a short action time with negligible copper losses. ...
... In order to quantify the UD level and associated performance degradation, an on-load demagnetization ratio k emf , which refers to the reduction ratio of the back-EMF fundamental magnitudes, is defined as [23] ...
This paper investigates the unintentional demagnetization (UD) characteristics of low-coercive-force (LCF) permanent magnets (PMs), in switched flux hybrid magnet memory machines (SF-HMMMs). Although the LCF PM field is magnetically in parallel to the magnetic fields produced by the NdFeB PM, as well as the armature reaction in the investigated machines, the UD phenomenon of LCF PMs still possibly occurs, particularly, under on-load operation due to the magnetic saturation effect. First, the UD effect is revealed by the frozen permeability method (FPM), and analytically explained via a magnetic circuit model. Various UD types are then identified with the finite-element (FE) method, coupled with a virtual linear hysteresis curve (VLHC) of LCF PM and FPM. In addition, the dimension and grade of the LCF PM are designed with the aid of VLHC, in order to prevent the UD effect. Finally, a fabricated SF-HMMM prototype is tested to verify the theoretical analyses.
... Furthermore, [110]- [111] have proposed the use of the thrust force to copper loss ratio as a comparison factor of linear machines. For the proposed CP FM-PMLSM, this ratio at 1m/s is 6.65 N/W. ...
... Moreover, the machine power factor is lower than the conventional machines. It has been reported previously that flux modulated machines suffer from the lower power factor due the issues like [110]. Several attempts have been made to improve the power factor such as the use of double-sided topology or two slot pitches winding etc. [112]- [113]. ...
The dissertation presents the design and analysis of a consequent pole flux modulated permanent magnet linear synchronous motor (CP FM-PMLSM) for long track application. Usually, for linear actuation applications in industry, surface permanent magnet linear synchronous motors (SPMLSM) are widely used. However, due to the presence of the permanent magnets (PMs) on the long stators, the cost of the SPMLSM based linear actuator systems increases as the track length increases. Therefore, to provide a low-cost alternative to the SPMLSM for long track applications like gantry robots, in this dissertation the design and analysis of the CP FM-PMLSM are proposed. The flux modulation principle of the CP FM-PMLSM is derived from the magnetic gearing effect inspired by the operation of the coaxial magnetic gear (CMG). Based on the magnetic gearing effect, the slot pole-pair numbers of the CP FM-PMLSM are decided. Next, the design process to find the optimal geometric and physical parameters is developed. The design process decides the parameters considering both magnetic and electric loadings under the condition to maximize the torque producing harmonic also known as working harmonic. During the design process, the help of the magnetic equivalent circuit (MEC) and the finite element analysis (FEA) are taken. Also, the design process considers the irreversible demagnetization of the permanent magnet (PM) by introducing nonlinear PM modeling and the effect of the PM magnetization direction is studied. Based on the optimal model obtained from the design process, the electromagnetic performance is analyzed next. To analyze the electromagnetic performance an extended mathematical model in the dqn reference frame is developed. The mathematical model considers the cross-coupling effect in the proposed CP FM-PMLSM resulting due to the presence of dual saliency. With the mathematical model, the consequences of the cross-coupling on the thrust characteristic are studied. It has been found that the cross-coupling produces a fluctuating thrust ripple component along with the average thrust. The results obtained from the mathematical model are validated against the 2D and 3D-FEA models. Furthermore, final model parameters are used to manufacture a prototype of the CP FM-PMLSM and different tests are performed by installing the model to a gantry system. The tests under no-load and different loading conditions are performed by varying the speed of the mover. Also, the dynamic operation of the system is checked under field-oriented control (FOC) using predefined speed reference commands. The electromagnetic losses are analyzed using Bertotti’s loss model and the efficiency is obtained using the three phase three wattmeter test. Moreover, the structural performance is checked by analyzing the noise and vibration and the causes of noise at the high-speed range are studied. To analyze the entry-exit point end effect on the machine performance like the mover’s initial position detection, a position detection algorithm including the compensation method for end effect is tested. Finally, the performance of the CP FM-PMLSM is compared with the commercial models to check its effectiveness in long track applications.
... (b)NS(p)-NS(p)-p partitioned stator DDMM[47].(c) NS(p)-NS(s)-p FS DDMM[48]. (d)NS(p)-NS(s)-p PS DDMM[48]. ...
... NS(p)-NS(s)-p FS DDMM[48]. (d)NS(p)-NS(s)-p PS DDMM[48]. ...
The field winding based flux adjustable permanent magnet (FWFAPM) machines, including the hybrid excitation topology and the memory topology, can offer excellent capabilities in terms of flux regulation, wide constant power operation as well as de-excitation (flux-weakening) under fault, thus, they are capable for using in More Electric Aircraft (MEA) generator systems. First, this paper probes four basic hybrid excitation modes, and based on that, a general method deriving PM machines to hybrid excitation machines is established. The basic characteristics of each hybrid excitation mode considering the relationship between S-pole and N-pole are obtained for the first time. The performance differences of each hybrid excitation mode combined with different PM machines are summarized. Then, this general topology derivation method are extended for the memory topology, The unified derivation method of the single-PM topologies, the double-PM topologies and the triple-PM topologies for memory machines is systematically established.The general laws of the electromagnetic performance of each double-PM mode and triple-PM mode considering different relationships between NdFeB and AlNiCo are summarized for the first time. Finally, the control strategies for voltage regulation of aircraft generator systems are discussed based on the different critical control variables and controller types, a torque impulse balance control method which shows excellent dynamic performance for both target control variable and critical control variable has been achieved experimentally.
... By controlling the polarity and amplitude of the field current, the corresponding speed range can be widened obviously [21][22][23] . To further widen the speed range and improve the efficiency, a type of memory motor equipped with low coercive force PMs has attracted considerable attention [24][25][26][27] , where the different magnetization of PMs can be online tunable by only injecting a d-axis current pulse temporarily. However, it is worth noting that the motors mentioned above mainly realize the widening speed range by flux regulation, yet, the efficiency and loss are not directly considered. ...
With the increasing complexity of electrical vehicles (EVs), the wide-speed-range high-efficiency characteristics of EV drive motors have been put forward in strict demand. In this paper, the “variable magnetic flux effect” is introduced into the permanent magnet (PM) motor, and the variable magnetic flux permanent magnetic (VMF-PM) motor is proposed. Firstly, by introducing the variable flux leakage topology, the flux can be adjusted flexibly, so the speed regulation range and high-efficiency region can be broadened synchronously. Then, the efficiency analytical model is constructed, considering motor speed, current, and flux variation comprehensively. It is indicated that, by the purposeful design of variable flux leakage topology, the efficiency under high speed can be improved based on the theoretical investigation of the high-efficiency boundary. Besides, based on the finite element analysis, the performances before and after optimization of key parameters of the VMF-PM motor are investigated, including flux variable characteristics and efficiency characteristics. Finally, a prototype motor is built, and the experiments are carried out. Both theoretical analysis and experimental results verify that based on the assistance of the “variable magnetic flux effect”, the motor high-efficiency region is broadened effectively, which provides a potential research path for designing a wide-speed-range high-efficiency motor.
... By employing additional windings as an assisted excitation source, it is possible to flexibly regulate the air gap magnetic field of hybrid-excited permanent magnet motors. 9,10 It is also possible to make the air gap flux adjustable by using low coercivity PM materials, such as aluminum-nickel-cobalt (AlNiCo), and by adjusting the current pulse to directly change the magnetization state of the low coercivity PM. 11,12 Due to the lower coercivity of PMs, their torque density and efficiency are significantly lower than those of NdFeB PM motors. So, it is still full of challenges for lessrare-earth PM motors to realize broadened speed range and reduced loss, while maintaining competitive torque performances. ...
In this paper, a new hybrid permanent magnet variable leakage flux (VLF-HPM) motor is proposed. In order to enhance motor speed range, short arc-shaped and elliptical-shaped magnetic barriers are placed on the q-axis magnet circuit, realizing the so-called leakage flux effect. In addition, ferrite PMs are artfully designed, so self-leakage flux can be reduced while main flux is enhanced. The relationship among PM topology, flux barrier and flux-regulation capability are also investigated in detail. Finally, the electromagnetic performance of VLF-HPM motor is evaluated by the finite element analysis and compared with a conventional V-typed PM motor. It is noted that, compared with conventional V-typed PM motor, the VLF-HPM motor possesses lower core losses and a wider speed range, which offers a new research path for high-performance PM motor.
... [18] Presents the simple analytical modeling for switched flux memory machine. In [19], the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations. In [20], a new 12/7-pole FSPM motor is proposed and investigated by FEM. ...
... Combined winding (permanent magnet, armature winding and excitation current winding) has been done and its zero-dimensional, two-dimensional and threedimensional models are extracted and average torque quantities, torque pulses, torque Tooth and losses are obtained by considering saturation and demagnetization [22]. The structure of three permanent magnet machines that are different in terms of magnet placement (three different structures where the magnet is placed only on the stator, on the rotor, and on both the stator and the rotor) and has 12 stator poles for the pole are studied and different quantities of average torque, torque pulses, induced voltage and tooth torque are calculated by considering decay effect, end effect and unsaturated core with the help of finite element method and analytical model [23]. In a new structure for the permanent magnet machine with one moving part and two stators is introduced, whose stator has a back yoke of the stabilizing part, and this new structure with a linear induction machine with two stators and one moving part is quantitatively Induced voltage, thrust force, tooth force, losses and flux density are compared, and the quantities are calculated with the help of finite element method [24]. ...
... Analytical subdomain model for magnetic field computation in segmented permanent magnet switched flux consequent pole machine is studied in [24]. In the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations [25][26][27][28][29][30][31]. ...
... Presents the simple analytical modeling for switched flux memory machine [5]. In the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations [6]. In a new 12/7-pole FSPM motor is proposed and investigated by FEM [7]. ...
... Combined winding (permanent magnet, armature winding and excitation current winding) has been done and its zero-dimensional, two-dimensional and three-dimensional models are extracted and average torque quantities, torque pulses, torque Tooth and losses are obtained by considering saturation and demagnetization. [23] The structure of three permanent magnet machines that are different in terms of magnet placement (three different structures where the magnet is placed only on the stator, on the rotor, and on both the stator and the rotor) and has 12 stator poles for the pole are studied and different quantities of average torque, torque pulses, induced voltage and tooth torque are calculated by considering decay effect, end effect and unsaturated core with the help of nite element method and analytical model. In [24], a new structure for the permanent magnet machine with one moving part and two stators is introduced, whose stator has a back yoke of the stabilizing part, and this new structure with a linear induction machine with two stators and one moving part is quantitatively Induced voltage, thrust force, tooth force, losses and ux density are compared, and the quantities are calculated with the help of nite element method. ...
In this paper a 2-dimensional model by solving partial differential equations for single Rotor Double Stator Interior Permanent Magnet Brushless Synchronous Machine with Spoke-Type structure (SRDSIPMBSMWSTS) is formulated to predict ux density in air-gaps at only no load. After extracting relations are governing in each domain (magnetic potential vector and magnetic eld intensity), boundary conditions between each two domain that are in adjacent to each other are applied to determine unknown coe cients. Output results are compared to nite element analysis (FEA) yield from Maxwell software to validate this fast and accurate model.
... Analytical subdomain model for magnetic field computation in segmented permanent magnet switched flux consequent pole machine is studied in [24]. In [25], [26], [27], [28], [29], [30], [31] the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations. ...
In this paper, a model based on Fourier series is presented to predict value of flux density in airgap with respect to mechanical angle for double-stator, double-rotor reluctance motor (DSDRRM). The DSDRRM is an excellent choice to be used as the electric motor in hybrid electric vehicles (HEVs) due to integrating two rotors and two stators into a compact structure and robust structure but torque ripple in this type of machines is high then special and fast model is necessary to design that proposed model can help us to have fast design. Point to point components of radial and tangential for DSDRRM are shown in figures compared between proposed model and finite element analysis (FEA) that the approach can be used for the magnetic field calculation in DSDRRM with any combination of rotor-and stator-pole number eventually, after putting analytical outputs on numerical outputs, efficacy of proposed model is validated.
... [18] Presents the simple analytical modeling for switched flux memory machine. In [19], the memory flux principle is extended to switched flux structures, forming two newly emerged switched flux memory machines (SFMMs) with single-stator (SS) and dual-stator (DS) configurations. In [20], a new 12/7-pole FSPM motor is proposed and investigated by FEM. ...
This paper investigates a two-dimension analytical model for E-core flux-switching permanent magnet brushless machine (FSPMBM) with outer rotor. This method is used to consider the effects of teethes on both the rotor and stator with mathematical method based on integration moreover saturation effect is neglected. This analytical method is implemented for magnetic field calculations in E-core FSPMBM with outer rotor with any combination of rotor-and stator-pole number at no load. To calculate distribution of flux density, initially, the stator and rotor iron is assumed to be infinitely permeable and Maxwell equations are provided then use the boundary conditions at intersection of two sub-regions to find the unknown coefficients for extracting changes of flux density in airgap with respect to each angle and radios. In order to validate the extracted results, the proposed model results are compared with those obtained from finite element method (FEM).
... Analytical subdomain model for magnetic field computation in segmented permanent magnet switched flux consequent pole machine is studied in [35]. In [36], the memory flux principle is extended to switched flux structures, forming two newly emerged SFMMs with single-stator (SS) and DS configurations. In [30], a DS-FSPM is analyzed by frozen permeability method. ...
In this paper, a two-dimensional analytical model is presented for brushless double mechanical port flux-switching permanent magnet machines (BDMPFSPMMs). The BDMPFSPMM is an appropriate candidate to be employed as the electric motor in hybrid electric vehicles (HEVs) due to integrating two rotors and two stators into a compact structure. The radial and tangential components of the magnetic flux density are calculated due to permanent magnets and armature currents in each active region of the machine based on the subdomain method. The effects of the saliency on both the rotor and stator structures as well as their interactions are considered. The approach can be used for the magnetic field calculation in BDMPFSPMMs with any combination of rotor-and stator-pole number. Based on the computed magnetic flux density, electromagnetic torque, self and mutual inductances, flux linkage, induced voltage, local traction and unbalanced magnetic force are obtained. To validate the proposed model, the analytical results are compared with those obtained from the finite element method (FEM).
... However, the motors suffer from high copper loss and relatively less power density. In order to avoid the continuous copper loss, the HMMMs [8]- [10] are proposed with low coercive force magnets, which can realize flux regulation by different magnetization states. And yet, a complicated integration control system is required to limit further application. ...
A novel mechanical variable-leakage-flux interior permanent magnet machine (MVLF-IPMM) is proposed for electric vehicles (EVs) in this paper, which employs a mechanical flux-regulating device and auxiliary rotatable magnetic poles. The magnetic poles acting as the flux adjustors can be rotated by the additional device to vary the leakage flux in magnetic circuit and realize the adjustment of the PM flux linkage. Due to the flux-regulating effect, the flux distribution in this machine is complex and changeable. Therefore, the working principle is illustrated in detail. To obtain the perfect coordination between the dominant magnetic poles and auxiliary magnetic poles, a multi-objective optimization method is presented based on the parameter sensitivity analysis combining with the Coefficient of Prognosis (CoP). Then, some design parameters with strong sensitive are selected by the sensitivity analysis and the initial model of the proposed motor is optimized by utilizing the multi-objective genetic algorithm (MOGA). According to the result of the optimization, the machine performances of the initial and the optimal design under the different flux states are compared and analyzed to verify the validity of the new variable-flux motor and the optimization method.
... Moreover, the combination of the series and the parallel connected, i.e., the hybrid-magnetic-circuit type has been proposed [13]. The low coercive-force magnets can be mounted on the stator as the stator permanent magnet VFMM [14], [15]. With the stepwise magnetization control, the constant power speed range can be effectively extended [16]. ...
Variable flux memory machines (VFMM) use magnetization and demagnetization manipulations to adjust machine voltage, achieving wide-speed high-efficiency operation. The machine magnetization state manipulation is a critical concern in the VFMM control. Thus, this paper proposes an on-line magnetization state estimation and closed-loop control using the magnetization manipulation signals. The magnetization state manipulation requires voltage injection to create the manipulation current. The current shows non-linear response at different magnetization state because the current changes the magnets state and the machine saturation level. The flux change rate, which is calculated by the injected voltage and the current response, is affected by the non-linearity and utilized in the proposed method for the magnetization state estimation. The proposed magnetization state estimation achieves self-sensing characteristic because the signals in the estimation already exist in the magnetization state manipulation. Based on the estimated and the target magnetization state, the closed-loop magnetization state control is achieved by the voltage injection regulation.
... In recent years, a class of double air-gap field-modulation machines, such as double stator/rotor machines, has attracted attention due to the merit of high torque density or the advantage of dual mechanical port function [24][25][26][27][28][29]. However, the comparatively complicated structure brings some obstacles to the analysis of the flux densities in the inner and outer air-gaps. ...
The air‐gap magnetic field analysis of the field‐modulation double‐stator electrical excitation synchronous machine (FM‐DSEESM) is complicated due to its double stator and modulation‐ring rotor configuration. Aimed to investigate the influence of the each part of the machine on the magnetic fields in the air‐gaps, this study focuses on the permeance function analysis of FM‐DSEESM to reveal its air‐gap magnetic field distribution. Due to the limited physical space, the non‐ferromagnetic segments of modulation‐ring rotor in FM‐DSEESM cannot be regarded as infinitely deep slots. Therefore, by adding a new flux line in the non‐ferromagnetic segments, a new permeance function is proposed based on the calculation of the equivalent air‐gaps. Then, analytical results of flux densities in the air‐gaps are calculated and verified by finite element analysis. Finally, a FM‐DSEESM prototype is fabricated to prove the feasibility of the permeance functions.
... Therefore, surface-mounted VFPM [7], [8] and interior-mounted VFPM [9]- [12] have been proposed. The LCF magnets can be mounted on the stator as the stator permanent magnet VFPM [13], [14]. Efforts have been done to increase the overall efficiency [15], [16] and reduce the maximum magnetization current [17], [18], promoting the application of the VFPM. ...
Online magnetization current control is a critical concern of the variable-flux permanent magnet machine control. Increasing the magnetization speed benefits the machine system, which reduces manipulation losses and mechanical impact. Thus, this paper proposes an online trajectory prediction method that increases the DC-link voltage utilization, boosting the manipulation speed. The prediction method decouples the rotating voltage and the induction voltage in the machine model. The induction voltage is the source of di/dt, which influences the magnetization manipulation speed. The proposed method updates the maximum available induction voltage at every manipulation stage by excluding the rotating voltage from the DC-link voltage limitation. Based on the induction voltage, the magnetization current trajectory is predicted. The trajectory prediction is cooperated with a feed-forward current controller to increase the control dynamics. Verified by various experiments, the proposed method achieves fast manipulation speed with high control accuracy. Besides, the proposed method shows self-adaptive capabilities in variable-speed and variable-voltage conditions.
... In [61], [62], Yang et al. presented a 6/13-p FSPM memory machine as shown in Fig. 7(g), which can readily perform field adjustment with negligible energy consumption. In which, spoke-array NdFeB PMs and low coercive force (LCF) PMs are sandwiched between an inner stator pole and an outer stator ring, respectively. ...
Flux-switching permanent magnet (FSPM) machines have been gaining interest over the last few decades. This is due to the several advantages that this type of machines provides. These advantages include high torque density due to the flux-focusing effects, favorable thermal management due to the location of PMs on the stator, passive and hence robust rotor structure which is suitable for high-speed applications, etc. The two-part companion papers are going to provide a comprehensive analysis of FSPM machines in terms of opportunities and challenges. In the first part of these two-part series, it covers the principle theory, computation methods, various topologies of FSPM machines, and the comparison with other PM machines. Meanwhile, the basic performance characteristics and design requirements, viz. torque density, over-load torque capability, flux-weakening capability, fault-tolerance capability, as well as the latest development, are also provided.
... Because of better utilization of materials and high performance, three-phase PMSMs are the most common for the mentioned applications [1]. The dual air-gap PMSMs such as dual-stator PM synchronous machines (DS-PMSM) [4][5][6][7] and dual-rotor PM machines [8][9][10][11] offer much higher power density than the conventional ones because of the total output torque results from the torque components produced by the interactions in two air-gap flux densities. ...
... [5][6][7] The corresponding MS can be memorized based on the specific current pulse level, and hence the speed range can be further extended. [8][9][10][11] Furthermore, due to short time duration of the magnetizing current, VFMMs require less flux-weakening copper loss in high-speed area, [12][13][14] leading to high-efficiency operation within a wide speed range. 15 As a result, VFMM is extensively recognized as a competitive candidate for automotive applications. ...
This paper investigates the magnetization characteristics of variable flux permanent magnet (VF-PM) by using a simplified C-core magnetizer device with AlNiCo PMs. A combined methodology with magnetic circuit model, finite element analysis and Fourier series fitting hysteresis model is proposed. By means of the magnetic circuit analysis, the basic sizing parameters of the device are designed for the prototype manufacturing. A simple experimental setup including a device prototype, a Gaussmeter and H-bridge-converter-based magnetizing circuit is established. Then several experimental schemes are conducted to research the magnetization characteristics. According to the experimental results, a new numerical hysteresis model of AlNiCo PMs is proposed based on Fourier-fitting functions, which can be employed to correct the hysteresis model parameters used in finite element (FE) simulation. Finally, the correctness of the proposed Fourier-fitting hysteresis model (FFHM) is experimentally verified by the test results.
... The hybrid-excited motors may inevitably cause some drawbacks, namely additional copper consumption, efficiency reduction and temperature rise. Thus, to solve such problems, a new type of flux memory motor equipped with low coercive force PMs (LCF-PMs) have gained growing research interests [8][9][10]. Since the magnetisation states of LCF-PMs can be varied online by only injecting a pulse d-axis current temporarily, and the additional excitation loss can be ignored, the flux memory motors can maintain a relatively wide-speed range with high efficiency. ...
In this study, based on a magnetisation‐controllable dynamic reluctance network (MC‐DRN) model, an optimisation design method with an efficient modern evolution algorithm for the flux memory motor is proposed. To clarify the method conveniently, a doubly salient flux‐control memory (DS‐FM) motor is involved and taken as a design example. First, according to the motor topology, the detailed MC‐DRN model of the DS‐FM motor is built, in which the magnetisation state adjustment of the low coercivity force material is considered. During the optimisation design process, to meet the diverse design requirements of multiple operation modes, non‐dominated sorting genetic II is employed to obtain the trade‐off optimal design of the DS‐FM motor under different magnetisation states. Moreover, to verify the feasibility of the optimisation method, the electromagnetic performances of the motor in different operation modes are investigated in detail, and the results are compared with that obtained by the finite‐element method. Finally, a prototype is manufactured, and the experiments are carried out. The corresponding results not only validate the reasonability of the investigated DS‐FM motor but also prove the accuracy and the effectiveness of the MC‐DRN model and optimisation design method.
With the merits of high torque density, unintentional demagnetization (UD) withstand capability and satisfactory flux regulation range, series magnetic circuit variable flux memory machines (VFMMs) have been recently utilized in the new-generation household appliance, e.g., washing machine. However, the conventional series structure leads to the increase of cost and magnetization current amplitude due to a larger volume of permanent magnet (PM) material, which are unfavorable for the industrialization of this kind of machines in domestic appliance applications. In order to address the foregoing issues, a novel consequent-pole hybrid magnet VFMM (CPHM-VFMM) with dual-layer delta-type PMs is proposed and optimized for belt-drive washing machine application in this paper. The machine is geometrically characterized by a novel rotor-PM consequent-pole (CP) design, which replaces half of the magnetic poles with iron parts, thus increasing
d
-axis magnetic permeance to decrease the corresponding required magneto-motive-force (MMF) for flux regulation while maintaining satisfactory electromagnetic performance. The topology and operating principles of the proposed CPHM-VFMM are firstly introduced and analyzed. The air-gap flux density and flux regulation range of the machine are analytically identified with equivalent magnetic circuit method. Then the machine is optimized with multimode field-current coupled (MMFCC) solution considering the operation situation in the washing machine. Afterwards, the electromagnetic characteristics of the machine are evaluated and compared with those of a conventional VFMM by finite element (FE) method. It shows that the proposed CPHM-VFMM has the merits of smaller PM usage, higher torque density, lower flux regulation current, wider flux regulation range, as well as higher global efficiency compared with the conventional counterpart. A 36-slot/6-pole CPHM-VFMM prototype is manufactured and tested to validate the FE analyses.
This article presents a novel memory motor drive with integrated winding concept for traction applications. The key feature of the proposed idea is to integrate the excitation winding with armature winding, and hence eliminating additional magnetization winding to achieve online magnetization-state regulations. Hence, the spatial confliction of conventional memory motors can be solved. Upon implantation of the proposed design, the winding utilization, torque/power density and fault tolerant capability are significantly improved. Based on the field modulation theory, the air-gap flux densities under different magnetization states are derived quantitatively to provide design guideline in initial stage. The integrated memory motor drive is presented systematically to consolidate the field and armature windings. To illustrate the effectiveness of the proposed design, two other conventional memory motors are included for comparisons. It is revealed the presented memory motor with integrated winding concept exhibits 28% higher winding utilization, 43% higher torque/power density and 218% higher flux regulation capability than its counterpart with conventional separate windings. In addition, fault tolerant capability can be significantly improved by eliminating mutual coupling between two winding sets. Finally, a prototype is fabricated, and the experimental measurements are carried out to verify the presented concepts.
A flux switching permanent magnet (FSPM) motor is designed and optimized in this paper to achieve high torque density and expanded speed regulation range from a design viewpoint of pole-changing (PC). Based on the field modulation theory, the PM field in the FSPM motor is modulated by the stator and rotor teeth, generating rich harmonics with different pole-pair numbers in the air-gap flux density. By adopting an appropriate slot pole combination, working harmonics with different slot pitch angles are obtained to establish a basis of the PC-FSPM motor. Then, different working harmonics can be used to achieve different energy conversions with different winding configurations, so the PC operation can be performed to realize the high torque and wide speed regulation range by switching the working modes. Based on the field modulation theory, the operation principle of conventional and PC-FSPM motors are analyzed and compared. Then, according to the design principle of the PC-FSPM motor, a 24/22-pole PC-FSPM motor with the E-core is designed and optimized by a multi-level optimization method. Finally, the electromagnetic performances are analyzed by finite element analysis and the test results of the prototype have verified the feasibility of the motor.
This paper reveals the flux leakage design and modeling principle of a flux leakage controllable permanent magnet (FLC-PM) machine by considering driving cycles. The key is to obtain the relationship between flux leakage characteristics and multiple operating conditions. Based on the flux leakage controllable concept, an FLC-PM machine with an artfully designed flux leakage region is proposed. The design principle of the machine is investigated by analyzing the magnetic circuit of the machine in multiple operating conditions. The flux leakage factor is introduced to characterize the variable magnetic field in multiple operating conditions. On this basis, the mathematical model of the FLC-PM machine is deduced, and the driving characteristics of the machine are studied in detail. In order to evaluate the presented principle of the FLC-PM machine, a prototype is manufactured for experiments. Through the theoretical analysis and experimental testing, it is verified that the proposed principle is feasible and effective.
In this paper, two novel dual stator machines with different biased permanent magnet (PM) configurations are developed and comparatively studied. For the proposed machines, the PMs are only located in the inner stator, but with different configurations, i.e., surface-mounted PM (SPM) and interior PM (IPM), respectively. The machine topologies and operating principle are introduced first. Then, the electromagnetic characteristics, including open-circuit performance, torque characteristics, field weakening capability, loss and efficiency are comprehensively analyzed and compared by finite element method (FEM). The experimental validation are conducted to verify the FEM analyses.
In this paper, a flux-controllable permanent magnet (FC-PM) motor has been designed and optimized to achieve the optimal torque component distribution under different flux leakage conditions. The FC-PM motor can realize the flexible adjustment and control of air-gap magnetic field by reasonable flux bridge design, which further broadens the speed range of the motor effectively. The focus of the research is to analyze and optimize the torque characteristics in combination with typical operation conditions. Firstly, a motor topology is proposed, the mechanism of flux leakage and the distribution of torque characteristics are studied. Then, according to different flux leakage operation conditions, an optimization method considering the torque component distribution is newly proposed. Based on the proposed optimization method, the optimal motor can be obtained. Finally, the performance of the optimal motor is analyzed and compared with the initial motor. The comparison results indicate that, based on the proposed optimization method, the torque output capability is improved effectively while the desired leakage flux adjustment range is maintained.
This paper investigates the design methods and performance optimization of segmented-double-stator switched reluctance machine (SDS-SRM). Firstly, two segmented U-shaped single-stator SRMs are introduced, including inner-rotor and outer-rotor constructions. In order to enhance the torque and power density, these two kinds of single-stator SRMs are combined together to constitute an SDS-SRM. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated to obtain the optimal rotor structure, and the corresponding conduction phase sequences for double-stator excitation mode are also analyzed. Furthermore, the flux distributions of the inner and outer stators with different coil magnetic polarities configurations are researched, and it reveals that the phase windings both on inner and outer stators with NSSNNSSN polarities have better magnetic field decoupling characteristics. To evaluate the final topology of the proposed SDS-SRM, the static magnetic characteristics and dynamic performances are presented. Finally, the SDS-SRM prototype is manufactured and tested to validate the theory and simulation analyses.
This paper presents the effect of different magnetization pulse widths and methods on the back-EMF, no-load losses, and minimum inverter rating at different operating conditions of a variable flux permanent magnet synchronous machine (VF-PMSM/VFM). Precise information of the back-EMF helps to estimate the cogging torque and torque ripple. An accurate determination of the core loss leads to a better efficiency estimation and machine design. An experimentally determined minimum inverter rating reduces the cost of the motor drive system. An adaptive nonlinear filter is used to estimate the VFM back-EMF during the motoring mode. The VFM is often demagnetized and remagnetized by injecting a current pulse to achieve the high speed and high torque requirements. The sudden injection of a d-axis current pulse will change the magnet flux linkage and back-EMF harmonics. In this paper, harmonics present in the machine back-EMF due to different magnetization and demagnetization current pulse widths and magnetization methods are analyzed. Besides, the quality of the back-EMF for different speeds and machine no-load losses are presented for different magnetization levels. The minimum inverter sizing is determined for magnetizing current and magnetizing current at full load considering the minimum pulse amplitude and width to magnetize the VF-PMSM
In this paper, a variable-saliency-ratio permanent magnet (VSR-PM) motor is designed and optimized considering driving cycles. To satisfy the demands of multi-operation conditions of EVs, a variable resistance is adopted and a new variable-saliency-ratio design concept is proposed to enhance output torque, widen speed range and lower irreversible demagnetization risk effectively. A multi-objective optimization considering driving cycles is proposed, where the design objective of saliency ratio is firstly selected and optimized with multi-objective genetic algorithm (MOGA) method. Then, the operation performances of the motor in different operation conditions are investigated in detail. Finally, a prototype motor is built and tested. Both the simulation and experimental results verify the validity of the proposed method.
This paper investigates a multi harmonics linear primary permanent magnet vernier machine. With the adoption of un-uniformly distributed PM arrays along the air gap, richer harmonics are achieved and make its performance superior to the conventional linear primary permanent magnet vernier machine. Firstly, the structures are described and compared. Then, their operation principles are analyzed by flux modulation theory. Electromagnetic performances of two machines are analyzed and compared through the finite element and theoretical analysis. The results show that the multi harmonics linear primary permanent magnet vernier machine offers 15% higher thrust force density compared with the conventional linear primary permanent magnet vernier machine. Finally, the experiments on a prototype of the multi harmonics linear primary permanent magnet vernier machine are carried out for validation.
Partitioned stator (PS) machines employ two separated stators to accommodate armature windings and permanent magnets (PMs) respectively, alleviating the space conflict in stator-PM machines and hence boosting the torque density. However, the PM usage volume in PS machines is relatively large and thus the material cost is high, which is undesirable for the cost sensitive applications. In this paper, a PS machine employing ferrite PM is presented, which takes advantage of larger available space for PMs whilst balances the performance and cost. The electromagnetic characteristics of an optimized ferrite PS machine and an NdFeB PS machine are evaluated, together with a classic Prius2010 interior-PM (IPM) machine as a baseline. Meanwhile, the economic issues are considered. The results reveal that the NdFeB PS machine has higher torque density than the Prius2010 IPM machine but more expensive, while the ferrite PS machine can significantly reduce the cost and still exhibit good performance. The demagnetization behavior of the ferrite PS machine is evaluated and a new method to improve the demagnetization withstand capability is proposed. Moreover, the mechanical analysis is conducted for the cupped rotor of PS machines. Finally, a pair of small-scaled prototypes are manufactured to validate the predictions.
The partitioned stator switched-flux permanent magnet (PM) (SFPM) (PS-SFPM) machine is a novel stator-PM machine in which PMs and armature windings are separately placed in two different stators. Compared with the conventional SFPM machine with a single stator in which both PMs and armature windings are located, the PS-SFPM machine can generate higher torque density due to the utilization of the machine's inner space. In this paper, the magnetic gearing effect in the PS-SFPM machine is investigated in terms of air-gap field harmonics based on a simple magnetomotive force (MMF)-permeance model. It is found that the PS-SFPM machine is one type of magnetically-geared machine, in which the modulations of rotor iron pieces to the open-circuit PM and armature reaction fields are similar to those found in the magnetic gear and the conventional magnetically geared machine. The pole-pair numbers and rotating speeds of the air-gap field harmonics obtained by the MMF-permeance model are verified by finite element (FE) analysis. More than 93% of the average electromagnetic torque is contributed by the main air-gap field harmonics having pole-pair numbers (2i - 1)p PM and Nr,pm, (2i-1)pPM( i = 1,2,3) in a PS-SFPM machine with pPM-pole-pair PMs and Nr-rotor-pole. A prototype machine is fabricated and tested to verify the FE analysis.
High-torque and low-speed electrical drives are often employed for applications where mechanical gearing cannot be accommodated. On the other hand, permanent-magnet (PM) gear has drawn significant attention from both academies and industries due to the conspicuous merits, such as reduced acoustic noise, maintenance free, improved reliability, precise peak torque transmission capability, and inherent overload protection. In this paper, a magnetic-geared PM brushless motor is presented. It is a novel low-speed and high-torque motor which merges the advantages of conventional PM brushless motor and PM gear. Its topology and operation principle are introduced. Some techniques are employed to optimize and improve the motor performance, while the validity of the proposed techniques is verified with finite-element analysis. Moreover, an alternative operation condition, which can further reduce the motor speed and increase its output torque, is proposed and analyzed.
In this paper, a new type of memory motors, namely the dc-excited memory motor, is proposed and implemented. The concept of dc-excited memory is due to the nature that the magnetization level of permanent magnets (PMs) in the motor can be regulated by a temporary dc current pulse and be automatically memorized. Based on an outer-rotor doubly salient motor structure, the proposed dc-excited memory motor can offer effective and efficient online air-gap flux control. Hence, it possesses the advantages of mechanical robustness, high efficiency, and wide constant power operation region. Both simulation and experimentation are carried out to verify the validity of the proposed motor.
This paper present original structures of a permanent magnet synchronous polyphased machine based on the switching flux principle.
In this paper, two methods for flux linkage regulation in a starter/alternator with an axial-flux permanent magnet (AFPM) machine are proposed and compared. Desired regulation is achieved by two different mechanical solutions, each of them capable of modifying the amount of flux linkage through displacement of the two rotors in the AFPM machine. Constant power generation is thus achieved with very inexpensive devices that do not require external energy sources since energy in the airgap doesn't change. The main difference between the two proposed solutions is that the speed dependant device is ideally a constant voltage source while the torque-dependant device behaves as a constant current source. Even if some improvements are still needed, both devices introduce the totally innovative concept of mechanical flux weakening for AFPM power regulation in a wide speed range. Finally, the paper demonstrates that the introduction of these devices doesn't modify machine behavior in starting mode, so that the particular features of AFPM machines in terms of high torque density and overload capability remain unaffected
This paper proposes two novel partitioned stator (PS) memory machines (MMs) based on flux-reversal (FR) and switched-flux (SF) topologies, respectively. The proposed machines geometrically feature two separate stators with armature winding and hybrid PM excitations, i.e., NdFeB and low coercive force (LCF) PMs. The proposed PS machines can offer increased available inner stator space for hybrid PM, which is beneficial to the torque improvement. The machine topologies are introduced first in terms of possible PM types with parallel magnetic circuits. The design considerations for hybrid PM are analytically analyzed. Then, the electromagnetic characteristics of the two proposed machines are comprehensively compared by using finite element (FE) method. The commercially available Toyota Prius 2010 machine is referenced as a benchmark for comparison with the optimal PS machine having identical overall dimension in potential context of traction applications. Finally, The FE analyses are validated by experiments on a small-scaled demonstration machine.
This paper presents a partitioned stator switched flux memory machine (PS-SFMM) with triple magnets to enable expedient flux control with reduced converter power rating. Meanwhile, the torque/magnet cost ratio of the machine has been significantly improved without much compromise of the torque capability. Three kinds of permanent magnets (PMs), NdFeB, SmCo, and AlNiCo, are hybridized, and hence the irreversible demagnetization of vulnerable AlNiCo PMs can be well prevented by SmCo magnets. The machine configurations with dual PM (DPM) and triple PM (TPM) are described first. Thereafter, the performance improvement mechanism is unveiled and addressed in the perspective of hysteresis curves as well as simplified magnetic circuits. In addition, the electromagnetic characteristics of the proposed machine with triple-magnet design are investigated and compared with those having DPMs. Finally, two PS-SFMM prototypes with DPM and TPM are manufactured and tested to verify the theoretical analyses.
As a topology of novel brushless permanent magnet (PM) machines, stator-PM brushless machines having magnets and armature windings in stator (the so-called stator-PM machines), exhibit the merit of convenient heat dissipations. The compact and robust rotor structure also makes stator-PM machines potential candidates for high speed applications. Meantime, the air-gap flux regulations can be realized by hybrid excitations of PMs and field windings, which consequently expands the speed adjustment regions. Overall, the stator-PM machine features the definite advantages of robust structure, high power density and efficiency, high fault-tolerant capability and being applicable of various control strategies. In this paper, a comprehensive and systematical overview on the stator-PM brushless machine systems and their key technologies is conducted, with particular emphasis on machine topologies, operation principles, design and analysis features, and control strategies. Furthermore, the flux- regulation strategies and fault-tolerant control strategies are presented. Some potentials of feasible applications for the stator-PM brushless machines in electrical vehicles, flywheel energy storage system, and urban rail transit, are discussed. Finally, the future trends are prospected.
The paper presents a design procedure for tangentially magnetized variable flux machines that aims to reduce the machine inverter rating. The proposed design can achieve high torque density at low speeds, and high efficiency at an extended speed range, as armature d-axis current pulses are applied at high speeds to reduce the magnet flux, thus avoiding the flux weakening current in conventional permanent magnet synchronous (PMSMs) machines. In order to regain the full torque capability when the motor slows down, a magnetizing current pulse has to be applied. The amplitude of the magnetizing current is usually larger than the machine rated current. Therefore, the machine might need an oversized inverter in order to be able to re-magnetize the magnets. The impact of different machine design parameters on the magnetization current requirement is investigated in order to reduce the inverter cost.
Several switched flux permanent magnet (SFPM) machines with mechanically movable flux adjusting technique are proposed, analyzed, and compared for applications which demand high speed and efficiency. By using ferromagnetic pieces-–one per every stator pole or every alternative stator pole, which are named as flux adjusters (FAs) and located on the outside surface of the stator—the airgap flux density can be weakened and therefore the operation speed range and flux weakening capability can be improved. The influence of using all or alternative FAs on the open circuit results, electromagnetic performance, and torque–speed characteristics of the SFPM machine is investigated through three SFPM machines with different stator/rotor pole combinations, i.e., 12/10, 12/13, and 12/14. Moreover, although using FAs in all stator poles can significantly improve the flux weakening capability, alternative FAs can also achieve remarkable improvement although higher torque ripple is observed. Additionally, it has been found that the 12/13 combination is considered to be the most suitable candidate for alternative FAs technique. In addition to 2-D finite-element analysis (FEA) and analytical methods, 3-D FEA results accounting for the end-effect are presented. Furthermore, experiments are performed to validate the results.
In this paper, the operational envelops and efficiency maps of an electrically excited (EE) machine with/without employing flux weakening control via armature current and/or with/without the field excitation regulating are obtained and comprehensively compared for electric vehicle applications. It shows that even in EE machines, only using the field excitation regulating but without the flux weakening armature current control, the maximum power at high speed is not constant but inversely proportional to the machine speed. Only by employing the flux weakening armature current control, the maximum constant power operation at high-speed region can be achieved while the operational high-speed region can be greatly extended. The maximum efficiency in this extended high-speed region can be achieved when both the field excitation and flux weakening ${d}$ -axis armature current change proportionally. The main benefit of the field excitation regulating is that the efficiency in low-torque region can be significantly improved. All the analyses are validated analytically.
A novel switched flux permanent magnet (PM) machine with a partitioned stator structure is proposed, consisting of a conventional switched flux machine with the PMs removed from the stator teeth and placed on a secondary stator within a salient rotor. This novel machine harnesses two distinct synergies in machine design: magnetically geared and switched flux machines. The machine is optimized and the performance is compared with different numbers of rotor poles and validated by experiment. This machine benefits from reduced copper loss, improved torque density, and torque per magnetic volume, compared with conventional switched flux machines.
This paper describes a variable magnetomotive-force memory motor with a fractional-slot concentrated winding. We propose a method for optimal control of magnetization suitable for a fractional-slot concentrated winding. Our result shows that variable magnetized magnets are more highly magnetized when a fractional-slot concentrated winding is used than those using the conventional method.
This paper presents a design approach for interior permanent-magnet (IPM) machines with variable-flux characteristics using low-coercive-force magnets for improved efficiency and extended operating speed range. A flux-intensifying IPM type with $L_{d} > L_{q}$ is used in the design due to positive $I_{d}$ operation and reduced loaded $I_{q}$ effects. Design considerations of machine structures and variable-flux machine attributes are discussed. In addition, leakage flux in a rotor is particularly designed to also obtain another flux-varying capability. Evaluation of the designed machine is provided by finite-element analysis simulations and experiments on a proof-of-principle machine. The designed machine shows benefits in increasing efficiency and speed range in a low-torque region when variable magnetization control of the low-coercive-force magnets or the design of the leakage flux proposed in this paper is implemented.
This paper presents a novel switched-flux memory motor (SFMM) by artfully incorporating the flux-mnemonic concept into the conventional switched-flux permanent magnet machine. The magnetic susceptibility of AlNiCo PM provides the flexible online controllability of air-gap flux by imposing a transient current pulse. To uniformize magnetization levels of PMs, a time-divisional magnetization strategy (TDMS) is proposed. Due to the uniqueness of hysteresis nonlinearity and instability regarding AlNiCo PM operating point, the time-stepping finite element method (TSFEM) dynamically coupled with a nonlinearity-involved parallelogram hysteresis model (NIPHM) of AlNiCo PM is performed to investigate the electromagnetic performance of the proposed SFMM. The results derived from the combinative algorithm verifies the flux-adjustable capability of the proposed motor equipped with TDMS and the validity of the proposed NIPHM.
This paper proposes and implements a new topology of hybrid excitation doubly salient brushless dc generator (HEDS-BLDCG). Configuration and flux control principle of the generator are presented. Two-dimensional finite-element methods are used to investigate the static field distribution characteristics of this new type of generator. Field-circuit coupled analysis is successfully performed, and the output characteristics of different windings are obtained. A prototype HEDS-BLDCG is designed and developed, and the experimentation is also given to verify the validity of the proposed brushless dc generator with one and dual terminal outputs. The results confirm the excellent field-regulation capability of HEDS-BLDCG, and the rectified output of the permanent-magnet part can serve as the independent power of the excitation winding when the HEDS-BLDCG has two sets of output windings.
A parallel hybrid excitation flux-switching (PHEFS) generator dc power system is presented in this paper. The PHEFS topology is proposed to achieve good flux regulation capability of the system as well as capability of deexcitation at fault and avoid permanent magnet (PM) magnetic shortcircuit and demagnetization. In order to improve the system's steady state and dynamic performance, a direct torque linear control (DTLC) scheme is proposed then. This DTLC scheme, which contains a voltage loop only and develops the direct linear relationship between the torque and sinusoidal value of the torque angle, can regulate the instantaneous torque directly and smoothly without current loop. The flux-weakening control of the DTLC scheme is also studied; the PHEFS generator system with excellent dynamic performance and lower flux and torque ripple has been achieved experimentally.
In this paper, a new type of memory motor, namely flux memory doubly salient motor, is proposed and tested. The key is to incorporate both the online tunable permanent magnets (PMs) and magnetizing windings into a stator-permanent-magnet motor. Thus, the resulting new memory motor can offer effective and efficient flux control. The design method of the memory motor is presented in detail. By combining a piecewise-linear hysteresis model with the finite element method, the static and transient electromagnetic performances are investigated. Experimental results of the prototype are given to verify the validity of the proposed motor. Index Terms—Doubly salient, electric vehicle (EV), flux memory, stator-permanent-magnet motor.
Magnetic-gearing effect has become increasingly at- tractive when designing direct-drive low-speed permanent-magnet machines. The machines derived from the magnetic-gearing ef- fect can be termed as harmonic machines. Unlike the conventional types, harmonic machines rely on the field harmonics to achieve energy conversion and transmission. The detailed knowledge of the field distributions in the air gap is vitally important for pre- dicting and optimizing its performance. In this paper, we present an analytical approach to calculate the magnetic field distribution in a low-speed permanent-magnet harmonic machine. A series-slot model which is composed of a group of partial differential equa- tions concerning the scalar magnetic potential is built up. Then, the field solutions are obtained by using the method of separating variables and analyzing the field boundary conditions. Finally, the flux densities are derived from the scalar magnetic potentials. All the results agree well with those obtained from the finite element method.
Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.
A method is proposed for predicting the flux-weakening performance of permanent-magnet (PM) brushless ac machines accounting for skew and d-q axis cross-coupling. The method is based on a d-q-axis flux-linkage model, a hybrid 2-D finite-element (FE)-analytical method being used to predict the d- and q-axis inductances. However, it only requires 2-D FE analysis of the magnetic field distribution over a cross section of the machine. The developed method is used to predict the torque-speed characteristic of an interior PM brushless ac machine with one stator slot-pitch skew. This is compared with predictions from a direct FE analysis of the machine and validated by measurements.
Permanent magnet (PM) brushless machines having magnets and windings in stator (the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure, high power density, high efficiency, etc. In this paper, an overview of the stator-PM machine is presented, with particular emphasis on concepts, operation principles, machine topologies, electromagnetic performance, and control strategies. Both brushless ac and dc operation modes are described. The key features of the machines, including the merits and drawbacks of the machines, are summarized. Moreover, the latest development of the machines is also discussed.
A new class of permanent-magnet (PM) machines, named memory motors for their ability to change the intensity of magnetization and memorize the flux density level in rotor magnets is described in the article. A memory motor can be built either as a variable-flux or pole-changing machine. In both machine types, the magnetization of PMs can be simply varied by a short current pulse, with no need for permanent demagnetizing current as in conventional internal PM machines at flux-weakening mode. The demagnetizing current flows through stator winding(s) supplied from the same source as the stator current. Memory motors combine advantages of a wound-rotor machine (variable rotor flux) with those of a wide-speed machine (no excitation losses), resulting in a unique machine concept that has the potential to find numerous applications in electric drives.
The paper examines the theoretical and practical limitations to
the field-weakening performance of surface permanent magnet, synchronous
reluctance and interior permanent magnet motors when driven from an
inverter with a limited volt-ampere rating. It is shown that the
`optimal' field-weakening performance consists of an infinite
constant-power speed range but is limited to an inverter utilisation of
about 0.7. The new concept of the interior permanent magnet parameter
plane is introduced. This graphically illustrates the effect of varying
the drive parameters on the shape of the field-weakening characteristic.
The interior permanent magnet parameter plane is used to show that there
are three types of optimal field-weakening designs. When practical
factors and considerations are taken into account, the optimal
high-saliency interior permanent magnet motor design is the most
promising for applications requiring a wide field-weakening range. A 7.5
kW design was built and a constant-power speed range exceeding 7.5:1 was
demonstrated
This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cell vehicles, with particular emphasis on PM brushless machines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operating range, and a high maximum speed capability, as well as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improving the torque and power capability, are described
High-power and high-efficiency permanent-magnet reluctance motor for hybrid electric vehicle
- K Sakai
- K Hagiwara
- Y Hirano
K. Sakai, K. Hagiwara, and Y. Hirano, "High-power and high-efficiency
permanent-magnet reluctance motor for hybrid electric vehicle,"
TOSHIBA REVIEW Japan, vol. 60, No.11, pp. 41-44, Sep. 2005.
Design and evaluation of a variable-flux flux-intensifying interior PM machine
- N Limsuwan
- T Kato
- K Akatsu
- R Lorenz