Hybrid Permanent Magnet Research Articles

Mode recognition and coordinated magnetisation control method for variable flux memory machine

The hybrid permanent magnet (PM) variable flux memory machine employs high- and low-coercive-force hybrid PMs to simultaneously obtain a high torque density and regulable PM flux property. The operating trajectories and steady working-points of this type of machine switch back and forth in multiple regions. To identify operating modes under various PM magnetisation states and speed ranges, this paper proposes a mode recognition and coordinated control method based on probabilistic neural networks (PNNs). A PNN algorithm is trained offline and executed in real-time to obtain a certain operating mode with the maximum probability of current state. According to the mode recognition result, a coordinated control scheme for applying short-time pulses or continuous flux-weakening current in a reasonable manner is presented. The proposed method exhibits an excellent capability in real-time operating modes identification, hence achieving magnetisation current control of multiple modes easily. Its feasibility and effectiveness are validated by experimental results on a hybrid PM VFMM prototype.

Design and analysis of a two-phase brushless DC motor with hybrid permanent magnet material for only-pull drive technique

This paper proposes a two-phase radial flux brushless DC motor comprising a rotor decorated with hybrid permanent magnet (PM) material, i.e., rare-earth NdFeB magnets combined with ferrite magnets. The rare-earth NdFeB magnets are used on the surface, and ferrite magnets in the spoke-type configuration. The combined surface and spoke-type topology are used to improve the output torque as well as to protect magnets of different grades against irreversible demagnetization. The motor is operated using the only-pull drive technique, which allows the use of thin magnets in the motor without the effect of irreversible demagnetization. The electromagnetic performance of the proposed motor is compared with those of a two-phase surface-type PM motor and the spoke-type motor, all driven by the only-pull drive technique. Furthermore, the operating point of the ferrite magnets is analyzed using finite element analysis to confirm the demagnetization endurance of the proposed motor.

Design and Optimization of a Hybrid Excitation System for Magnetically Driven Rotating DC Arc Plasma Generators

To eliminate the disadvantages of both the uncontrollability in the magnetic field of a permanent magnet excitation system and the high energy consumption of an electric excitation system in a traditional magnetically rotating arc plasma generator, a novel topology of a hybrid permanent magnet and electrically excited coil system is proposed. The proposed system will generate a large enough magnetic field to drive the arc rotation with a minimum consumption of materials and electric energy in the normal operation duty, and will guarantee a nearly zero magnetic field in the arc triggering stage. To optimize the hybrid excitation system, a comprehensive analysis and an optimization methodology; by combining finite element analysis, the moving the least squares approximation and an adaptive weighted particle swarm optimization, are proposed. Finally, a prototype hybrid excitation system is optimized with promising results in views of both saving a huge amount of electric power consumptions and ensuring a nearly zero magnetic field in the arc triggering.

Implementation and suspension force evaluation of a permanent magnet hybrid type magnetically levitated carrier system

Implementation and suspension force evaluation of a permanent magnet hybrid type magnetically levitated carrier system

Investigation of Hybrid-Magnet-Circuit Variable Flux Memory Machines With Different Hybrid Magnet Configurations

This article investigates and compares the electromagnetic performance of two novel hybrid-magnetic-circuit variable flux memory machines (HMC-VFMMs) with different hybrid permanent magnet (PM) configurations. The investigated HMC-VFMMs are both geometrically characterized by a combination of series and parallel magnetic circuit topologies, but with different positions of series and parallel PM branches. The developed HMC design can combine the merits of wide flux adjustment range in parallel structure and excellent unintentional demagnetization withstand capability in series structure. The topologies, features, and working principles of the studied HMC-VFMMs with different hybrid magnet configurations are described, respectively. The magnetic circuit model is utilized to analytically reveal the performance metrics of the two machines. The electromagnetic characteristics of the radially magnetized (RM) and circumferentially magnetized LCF types of HMC-VFMMs are evaluated and compared by the finite-element method. Furthermore, the performance comparison of the proposed RM-type HMC-VFMM with a benchmark interior PM machine is conducted. The experiments on RM-type HMC-VFMM prototype with RM-structure are carried out to validate the FE analyses.

Computationally efficient hybrid PM loss prediction method for surface‐mounted permanent magnet machine over entire working conditions

This study proposes a computationally efficient hybrid approach to calculating permanent magnet (PM) loss in surface-mounted PM machine (SPMM) over the whole working points. By analysing the impact of current amplitude, current angle, rotor speed, and PM temperature on the corresponding subdomain PM loss results, a simplified model that considers harmonic current and explicitly expresses the relationship between PM loss and working point variables is derived. Unlike the corresponding subdomain method, the proposed model does not involve a Fourier expansion or summation over a large number of terms, which simplifies the calculation and makes the PM loss under any operating condition can be acquired instantly. Thus, the needs for PM loss table and massive experiments or calculations are eliminated. The accuracy of this hybrid approach is validated against the finite element method results of a six-phase SPMM over a wide range of working conditions. However, the cross-verification studies demonstrate that the proposed method has good efficiency and high precision, making it a promising tool for online PM loss prediction.

Development of Brushless Claw Pole Electrical Excitation and Combined Permanent Magnet Hybrid Excitation Generator for Vehicles

Aiming at the problems of large excitation loss and low power generation efficiency of silicon rectifier generators and the unstable output voltage of permanent magnet (PM) generators, a hybrid excitation generator (HEG) with suspended brushless claw pole electrical excitation rotor (EER) and combined magnetic pole PM rotor is proposed in the present work. With only one fractional slot winding stator, the generator adopts PM field as the main magnetic field and electrical excitation field as the auxiliary magnetic field, which not only retains the advantages of high efficiency of PM generators but also effectively reduces excitation consumption. The main structure parameters and the design method were analyzed, and a simulation analysis of no-load magnetic field distribution and flux regulation ability was carried out using finite element software to verify the rationality of the hybrid excitation parallel magnetic circuit design. Moreover, the no-load, load, regulation, and voltage regulation characteristics of the designed generator were tested, and the results show that the designed generator has a wide range of voltage regulation, which can ensure stable output voltage under variable speed and load conditions.

A Novel Stator Flux-Concentrated Hybrid Permanent Magnet Memory Machine

This article proposes a novel stator flux-concentrated hybrid permanent magnet memory machine (SFC-HPM-MM), which features that its armature windings, magnetizing coils, and U-shaped hybrid PMs are all located in stationary side. Besides, the salient rotor pole exhibits high robustness and simple manufacturing. The low-coercive-force (LCF) PM magnetization state (MS) can be regulated by temporarily applying a current pulse in magnetizing coils, which means that online magnetization variability can be achieved. Due to the consequent-pole hybrid PM arrangement, this new topology exhibits reduced required magnetization current level, good flux concentrated effect, and increased torque capability. The machine topology and operating principle are introduced first. Subsequently, the multi-objective genetic algorithm is adopted to optimize the design parameters of the proposed machine on the basis of optimizing rotor pole number. Finally, the electromagnetic performance of the machine is investigated by finite-element (FE) analysis, which confirms the feasibility of the proposed design.

A new fault-tolerant switched flux machine with hybrid permanent magnets

This paper put forward a new fault-tolerant hybrid switched-flux PM (HSFPM) machine design employing the synergy of NdFeB and Ferrite Magnet. The key of the proposed HSFPM designed machine is the unique design E-core laminated stator with the hybrid magnet to ensure a drastic reduction of NdFeB magnet without compromising the output performances and efficiency in the conventional SFPM machine design to avert the huge demand of NdFeB and its associated volatile high price increase. Additionally, the fault-tolerant stator teeth designed principle implemented in the proposed HSFPM machine provides enhanced segregation among the various phases and ensures continuity of operation with acceptable operating performance under fault-condition. For fair evaluation and comparison, both the proposed HSFPM and the conventional SFPM (CSFPM) machine have the same slot-pole combination, winding arrangements, and stator/rotor dimensions except for the unique outer-stator of the proposed design. Meanwhile, compared to the CSFPM machine, the proposed HSFPM machine design makes use of only 60% of the PM (NdFeB) length. Finally, the evaluation of the no-load in conjunction with the load condition performances was carefully investigated by the Finite Element Method (FEM) of the ANSYS Maxwell software. The results depicted that the proposed HSFPM exhibits similar sinusoidal back electromotive force, comparable output torque, and slightly higher efficiency compared to that of the CSFPM machine.

3D Analytical Model of Permanent Magnet and Electromagnetic Hybrid Halbach Array Electrodynamic Suspension System

In this paper, a 3D analytical model of permanent magnet (PM) and electromagnetic hybrid Halbach array electrodynamic suspension (EDS) system for a conductive plate is presented. When the hybrid Halbach array moves to cut the conductive plate, the 3D eddy current forces are derived using the second-order vector potential (SOVP) based on y-component of the source magnetic flux density, which is derived using the Biot–Savart law and surface current method. The accuracy of the derived equations is verified by a 3D finite-element analysis (FEA) model. Furthermore, the effects of the main characteristic parameters on the levitation force are analysed.

ICE/HPM generator range extender for a series hybrid EV powertrain

This study discusses an optimised auxiliary power unit for applications in series hybrid electric vehicles (SHEVs). The auxiliary power source consists of an internal combustion engine (ICE) and a hybrid permanent magnet (HPM) generator. The ICE acts as a prime mover to the HPM generator the electrical output of which is connected to the vehicle DC-link via a passive rectifier. The vehicle primary energy is supplied by a ZEBRA battery system while the ICE/HPM generator provides a range extension. The SHEV performance is evaluated over some driving cycles using performance indicators such as driving range, fuel consumption, emissions and, battery utilisation. A dynamic model of the ICE/HPM generator system is developed and a vehicle range, with consideration of the battery dynamics, is numerically evaluated via a simulation platform. The predicted results are compared with measurements from a laboratory prototype HPM generator system, which shows a good agreement hence validating the models and simulation platform.

Comparative Study on Variable Flux Memory Machines With Different Arrangements of Permanent Magnets

Compared with conventional permanent magnet synchronous motor, variable flux memory motor (VFMM) possesses the advantage of adjusting the magnetization state online. Because of its wide speed range and large high-efficiency region, it becomes a competitive candidate for the electric drive system. This paper presents a novel parallel hybrid magnets VFMM which is obtained by updating a conventional series hybrid permanent magnets VFMM. The proposed motor adopts a new permanent magnet arrangement and the combination of low coercive force permanent magnet and high coercive force permanent magnet is used. The proposed parallel hybrid permanent magnets VFMM and the series hybrid permanent magnets VFMM are compared. The equivalent magnetic circuit models of the motors are used to explain the principle of the motors. The finite element analysis method is used to study the fundamental properties, such as open circuit radial flux density, unintentional demagnetization with q-axis current, intentional demagnetization with d-axis current, torque capability, and efficiency characteristics. It was shown the efficiency of the parallel hybrid permanent magnets VFMM is higher in the high-speed region and the magnetization state adjustment range of the parallel hybrid permanent magnets VFMM is larger.

Research and Design on Reducing the Difficulty of Magnetization of a Hybrid Permanent Magnet Memory Motor

In this article, magnetic barriers setting on both sides of a low coercive force magnet (low-Hc) and forward/reverse magnetization process of a parallel memory motor are analyzed by using magnetic circuit method and finite element analysis (FEA). The results show that magnetic barriers on both sides of the low-Hc magnets can weaken the influence of high coercive force magnets (high-Hc) on the low-Hc magnets and improve anti-demagnetization ability of the low-Hc permanent magnets. At the same time, the motor has difficulties in forward magnetization. In order to reduce the difficulty in magnetization of the motor, a new type of parallel hybrid permanent magnet memory motor is proposed. The structure and the operation principle of the motor are elaborated in detail in the paper. The analysis results by using the magnetic circuit method and FEA show that the new structure can greatly reduce the magnetization current of the motor. Compared with the existing parallel hybrid permanent magnet memory motor, the improved motor has comparatively less difficulty in magnetization and stronger anti-demagnetization ability. Finally, a prototype is fabricated and the magnetization performance and efficiency of the motor is verified. The measured results show that the motor has advantages of low magnetizing current and high efficiency.

Characterization of a Hybrid PM Generator Using a 32-Phase Brushless Excitation Scheme

This paper presents characterization and operational envelope of a hybrid permanent magnet (HPM) generator in a series hybrid electric vehicle (SHEV) powertrain. A proposed control strategy is applied to characterize the system during vehicle operation within new european driving cycle (NEDC). The HPM generator utilizes a permanent magnet topology assisted with a wound field (WF) rotor while the machine 9-phase output is rectified and connected to the SHEV main dc-link. A brushless exciter with dc stator and multiphase rotor is designed to provide an adjustable dc current and voltage to the HPM generator WF. The brushless exciter dc stator is fed from the vehicle dc-link using a dc/dc converter while its rotor output connects to an integrated 32-leg rotating rectifier the output of which provides a high quality dc to the HPM generator WF. A control strategy incorporating a dynamic model of the HPM generator, brushless exciter, and dc/dc converter is proposed under which the system operational envelope is obtained. The HPM generator efficiency map, torque speed, and WF current behavior is analyzed to realize an optimum operating region while the SHEV operates over the NEDC driving cycle. The analytically predicted results are validated against measurements from a laboratory prototype HPM generator and exciter system. The comparison shows the effectiveness of the control method and accuracy of the developed models.

Design and Multi-Objective Stratified Optimization of a Less-Rare-Earth Hybrid Permanent Magnets Motor With High Torque Density and Low Cost

The price fluctuation and the unstable supply chain of rare-earth permanent magnet (PM) have posed potential risks for further application of rare-earth PM motors. To alleviate the consumption of rare-earth PM material, a less-rare-earth PM brushless motor with two types of PM materials is proposed in this paper. The key of this motor is that the rare-earth PM is purposely combined with a non-rare-earth ferrite PM, forming the hybrid PM excitation. To design the proposed motor efficiently, a multi-objective stratified optimization strategy is proposed, where the selected five optimization objectives of output torque, PM cost, cogging torque, torque ripple, and efficiency are divided into two levels. Then, different optimization methods are skillfully combined to meet the specific design requirements. The corresponding electromagnetic performances are analyzed and compared with the baseline rare-earth PM brushless motor. Finally, several experiments of the two motors are carried out for evaluation. Both theoretical analysis and experimental results verify the feasibility and validity of the proposed motor and the optimization method.

Design and Analysis of a Flux-Concentrated Linear Vernier Hybrid Machine With Consequent Poles

In low-speed applications, variable-reluctance permanent magnet machines are often proposed due to their efficient use of magnet material and high torque density. This becomes even more important in large linear applications, where the translator is longer than the stator. Often, however, very low power factors are experienced by this class of machines. This paper proposes a V-shaped flux concentrated version of a consequent pole linear Vernier hybrid permanent magnet machine and compares it to a surface-mounted magnet variant. Using finite-element analysis validated by two laboratory prototypes, it is shown that the flux-concentrated version increases the airgap flux density, which potentially leads to an improvement in the force density and efficiency or can be used to increase the operating power factor.

Influence of magnetic field strength of hybrid magnet on vibration isolation of quarter car model

This work studies the vibration isolation of a single degree of freedom (SDOF) quarter car model under the influence of the magnetic field strength of electromagnet of a hybrid electromagnet (EM) and permanent magnet (PM) combination. Furthermore, the time history plot helps to study the influence of the relative movement of the electromagnet and the permanent magnet on the top plate, base plate, stiffness of the system and damping coefficient. A laboratory scale model of a SDOF quarter car with a hybrid magnet is tested on an open loop type shaker table at different frequencies of base excitation. Data acquisition and analysis have been carried out with the aid of two piezoelectric accelerometers and Lab VIEW software. Also, the theoretical analysis is carried out in MATLAB Simulink. From the experimental and Simulink results, it is found that the repulsive force between the electromagnet and permanent magnet varies the base and top plate amplitude, the stiffness of the system and damping coefficient of the suspension elements.

Systematic multi-level optimization design and dynamic control of less-rare-earth hybrid permanent magnet motor for all-climatic electric vehicles

Motors that convert electrical energy to mechanical energy, have been considered as one of the most crucial components of all-climatic electric vehicles (EVs). In order to realize high-quality energy conversion, motor optimization has attracted considerable attention in the research field of motors. In this paper, systematic multi-level optimization design and dynamic control strategy is proposed for a less-rare-earth hybrid permanent magnet (LRE-HPM) motor. In the proposed systematic optimization strategy, the design requirements of the motor design level and control level are considered comprehensively. In the motor design level, the comprehensive sensitivity analysis is adopted to stratify design parameters, and the response surface method and multi-objective genetic algorithm are implemented respectively. In the motor control level, the resonance compensation strategy is established to further suppress torque ripple and speed vibration. Finally, a prototype motor is built and tested. Both simulation and experimental results not only verify the effectiveness of the proposed systematic optimization and dynamic control strategy, but also offer a research orientation for realizing high-quality energy conversion of all-climatic EVs.

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.

A Hybrid Interior Permanent Magnet Variable Flux Memory Machine Using Two-Part Rotor

In this paper, a novel hybrid permanent magnet variable flux memory machine using two-part rotor is proposed whose rotor comprises an AlNiCo part and a NdFeB part adjacent to each other on the same shaft. With the proposed topology, flexible flux controllability can be achieved since the magnetization state of AlNiCo can be adjusted by a temporary current pulse. The detailed operating principles are described, and the split ratio and some key design parameters are optimized. Then, the electromagnetic performance of the proposed machine with emphases on back electromotive force, flux density, flux-weakening performance, and torque characteristics is investigated. Finally, 3-D finite-element validation is implemented and a machine prototype has been manufactured and tested to validate the analyses.