Hybrid Excitation Flux Switching Research Articles

Investigation of a Partitioned-Primary Hybrid-Excited Flux-Switching Linear Machine With Dual-PM

A novel partitioned-primary hybrid-excited flux-switching linear machine with dual-PM excitation (DP-PPHEFSLM) is proposed and investigated in this paper. Unlike conventional single-primary hybrid-excited topologies, this proposed topology separates armature windings and field windings into two different parts of the partitioned-primary, with each part also having sandwiched or buried PMs. Due to greatly increased armature and field slot areas, it thus solves the problem of a crowded primary, which is typically encountered with conventional structures. Besides, the thrust density is further increased by skillfully positioning PMs on both primary parts. In this paper, first, the topology, operation principles, and viable primary/secondary pole-number combinations of the proposed machine are elaborately addressed. Based on 2D finite-element method (FEM), the proposed machines are globally optimized using genetic algorithms and their electromagnetic performances further investigated. Moreover, the proposed machine is compared with conventional topologies in terms of electromagnetic performances, which shows that the proposed machine exhibits multiple merits such as higher thrust density, improved space utilization, and more flexible flux control capability. Finally, a 6/7 DP-PPHEFSLM prototype machine is manufactured and tested to validate the 2D FEM-predicted results.

Maximum Ratio of Torque to Copper Loss Control for Hybrid Excited Flux-Switching Machine in Whole Speed Range

This paper proposes an optimized control strategy for hybrid excited flux-switching machine (HEFSM) in the whole speed range. First, the machine topology, operating principle, electromagnetic performance, and dynamic models of HEFSM are briefly introduced. Second, in the constant torque range, the optimized positive excitation is utilized to improve the load capacity, and minimize the copper loss, as well as achieve a faster response than the strategy of random combination of excitation and armature current and the zero excitation current control. In constant power range, there are several constraints like torque, current, voltage and speed. The optimized negative excitation current and d -axis current are not only used to achieve higher speed and produce reluctance torque, but also minimize the copper loss for a certain value of torque in the optimized strategy. Then, the maximum ratio of torque to copper loss is realized. Finally, other losses (such as iron loss, friction, and windage losses) and efficiency of HEFSM are analyzed. The feasibility and effectiveness of the proposed control strategy for the HEFSM drive system are confirmed by simulation and experiment.

Comparative Investigation of Hybrid Excitation Flux Switching Machines

In this paper, the effect of partitioned stator (PS) structure and iron flux bridges in hybrid excitation flux switching (HEFS) machines is comprehensively discussed and compared. Firstly, the operating principles of four HEFS machines with single stator and PS respectively with and without iron flux bridges are described. Then an equivalent lumped parameter magnetic circuit model is developed to analyze the characteristics of PS structure and iron flux bridges. In order to achieve a fair comparison among different HEFS machines, the multi-level design optimization method is used to obtain the optimal parameters efficiently, based on which the electromagnetic performances of four machines are comprehensively evaluated by using 2D finite element analysis (2D-FEA). The results reveal that the machines with PS structure can exhibit not only a better flux regulation capability but also a higher torque density than conventional HEFS machines. Moreover, by adopting iron flux bridges, enlarged wide constant power speed region (CPSR) can be achieved, but the PM utilization will be slightly sacrificed.

Cyclic Parameter Refinement of 4S-10 Hybrid Flux-Switching Motor for Lightweight Electric Vehicle

A great deal of attention has been given to the reduction of lighting the vehicle because the lighter the vehicle the energy consumption is comparatively low. Hence, the lightweight electric vehicle was introduced for lower carbon footprint and the sizing of the vehicle itself. One of the components to reduce the weight of the vehicle is the propulsion system which comprised of electric motor functioning as the source of torque to drive the propulsion system of the machine. This paper presents the refinement methodology for the optimized design of the 4S-10P E-Core hybrid excitation flux switching motor. The purpose of the refinement methodology is to improve the torque production of the optimized motor. The result of the successful improvement of the torque production is justifiable for a lightweight electric vehicle to drive the propulsion system.

Analysis of Permanent Magnet Demagnetization Effect Outer-rotor Hybrid Excitation Flux Switching Motor

This paper addresses the irreversible permanent magnet (PM) demagnetization analysis of hybrid excitation flux switching motor (HEFSM) with outer-rotor configuration. PM demagnetization cause the PM strength used in the motor significantly reduces and hence contributes less torque performance. The study is focused on thermal analysis and conducted at various temperature up to as high as 180 degrees Celsius which has a tendency to be demagnetized. Therefore, PM demagnetization is among a critical issue and influences the choice of the applied motor. The analysis is carried out based on finite element method (FEM) and percentage of PM demagnetization is then calculated. Finally, based on simulated and calculated results the final design outer-rotor HEFSM has only 0.85 percent PM demagnetization at very high temperature and obviously the is no PM demagnetization at normal operating conditions.

Investigation of a Five-Phase E-Core Hybrid-Excitation Flux-Switching Machine for EV and HEV Applications

In this paper, to improve flux-regulation and constant-power speed range, a 10-stator-pole/18-rotor-pole five-phase hybrid-excitation flux-switching (HEFS) machine with “E”-core stator cell is proposed and analyzed. The topology and operation principle are investigated first. Then, the different armature winding connection methods are evaluated to reduce the total harmonic distortions of phase permanent magnet (PM) flux linkages. Furthermore, based on a simplified magnetic circuit, the analytical power-sizing equations are derived to determine the main design dimensions and parameters of E-core HEFS machines with given performance specifications. The electromagnetic performance, including the conventional static characteristics, such as phase PM flux, back electro-motive-force, cogging torque, electromagnetic torque, and flux-regulation capability, is analyzed by means of two-dimensional (2-D) and 3-D finite-element analysis to take end effect into account. The predicted results indicate that the proposed five-phase E-core HEFS machine exhibits improved flux-regulation capacity and wide range of speed regulation. The performances of HEFS machine are verified by experimental results on a prototype machine. Therefore, the HEFS machine is a promising candidate for electric vehicle and hybrid electric vehicle applications especially for direct-driven systems where the wide range of speed regulation and high-efficiency performance are crucial.

Design and Comparison of Two Six-Phase Hybrid-Excited Flux-Switching Machines for EV/HEV Applications

Multiphase flux-switching permanent-magnet (FSPM) machines inherit the merits of conventional FSPM machines and the common advantages of multiphase machines, e.g., low torque pulsations, a high torque density, and a high fault-tolerant capability. When a hybrid excitation is applied, postfault armature currents can be reduced by applying a positive field current (PFC). Hence, in this paper, based on both 2-D and 3-D finite-element analyses (FEAs), two six-phase hybrid-excited flux-switching (HEFS) machines with E-core and C-core stator laminations are designed, respectively. Iron bridges are adopted in each machine, and the influences on the performance are investigated. In addition, alternative-tooth-wound armature windings are employed in the C-core machine to obtain physical and magnetic isolations between armature phases. A comprehensive comparison of the two designs is carried out. Then, more attention is paid to fault-tolerant operating capabilities when an open-circuit fault occurs to only one phase and two phases of armature windings, respectively. The PFC can be applied in the C-core machine under fault-tolerant operating conditions; thus, the postfault armature current can be reduced while maintaining the torque output. Overall, the torque output can be effectively maintained in each HEFS machine during postfault operations. Finally, the FEA-based studies are validated by experimental measurements on two HEFS machine prototypes.

Steady-State Characteristics Analysis of Hybrid-Excited Flux-Switching Machines with Identical Iron Laminations

Since the air-gap field of flux-switching permanent magnet (FSPM) machines is difficult to regulate as it is produced by the stator-magnets alone, a type of hybrid-excited flux-switching (HEFS) machine is obtained by reducing the magnet length of an original FSPM machine and introducing a set of field windings into the saved space. In this paper, the steady-state characteristics, especially for the loaded performances of four prototyped HEFS machines, namely, PM-top, PM-middle-1, PM-middle-2, and PM-bottom, are comprehensively compared and evaluated based on both 2D and 3D finite element analysis. Also, the influences of PM materials including ferrite and NdFeB, respectively, on the characteristics of HEFS machines are covered. Particularly, the impacts of magnet movement in the corresponding slot on flux-regulating performances are studied in depth. The best overall performances employing NdFeB can be obtained when magnets are located near the air-gap. The FEA predictions are validated by experimental measurements on corresponding machine prototypes.

Investigation of an Improved Hybrid-Excitation Flux-Switching Brushless Machine for HEV/EV Applications

In this paper, based on 2-D finite-element analysis (FEA), the hybrid-excitation principle of a hybrid-excitation flux-switching (HEFS) machine is analyzed, and consequently, an improved topology is proposed to enhance the flux-regulation capability. These two machines are termed as the basic HEFS machine and the improved HEFS machine, respectively. In the basic HEFS machine, each permanent magnet (PM) is located at the middle of the corresponding slot and wound by a field winding coil. When field excitation is applied, it is found that the currents in the two field slots adjoining each PM exhibit reversal excitation functions, thus reversal flux-regulation functions. Hence, to improve the flux-regulation performances, an improved HEFS topology is proposed based on the basic one by reversing current direction in one of the field slots. Therefore, the improved topology shares identical structure with the basic one but has different field current directions in some field slots and thus different field winding accommodations. Comparisons of the FEA predictions indicated that both armature no-load flux-regulation capability and armature load torque capability in the improved HEFS machine are much better than those in the basic one. Finally, the FEA results are validated by experimental measurements on two prototyped HEFS machines.

Flux-Regulation Theories and Principles of Hybrid-Excited Flux-Switching Machines

A hybrid-excited flux-switching (HEFS) machine was proposed by reducing the permanent-magnet (PM) length of an original flux-switching PM machine and introducing a set of field windings into the saved space. According to the PM locations, three typical topologies of HEFS machines emerged, namely, PM-Top, PM-Bottom, and PM-Middle, respectively. The preliminary analysis indicates that different configurations of magnets and field windings have significant influences on the electromagnetic performance of HEFS machines. Hence, this paper is focused on the flux-regulation theories and principles of the three topologies of HEFS machines employing two typical magnet materials, namely, ferrite, and NdFeB, respectively. It is found that the field winding in the PM-Top machine exhibits reversal flux-regulation functions to that in the PM-Bottom one. The weakest flux-regulation capability is found in the PM-Middle one, since this can be considered as a combination of PM-Top and PM-Bottom ones. Overall, the highest magnet utilization and a strongest flux-regulation capability are exhibited in the PM-Bottom HEFS machine. The theoretical analysis is validated by both 2-D finite-element analysis-based predictions and experimental measurements on three prototype HEFS machines.

Performance Comparison of 12S-14P Inner and Outer Rotor Field Excitation Flux Switching Motor

Hybrid excitation flux switching machines (HEFSMs) have a several advantages such as robust rotor structure, high torque and power capabilities, and high efficiency suitable for light load and heavy industry applications. However, the general structure of HEFSMs employed with three main flux sources namely permanent magnet (PM), field excitation coil (FEC) and armature coil located on the stator body causes high manufacturing cost. Therefore, a new non-PM field excitation flux switching machine (FEFSM) consists of rugged rotor structure suitable for high-speed operation with capability to keep similar torque and power density of HEFSM is proposed and examined. In this paper, performances of both outer and inner rotor 12S-14P FEFSMs are analyzed and compared. As conclusion, the inner-rotor topology provides much higher torque and power when compared with outer rotor configuration.

Optimization of Single Phase E-Core Hybrid Excitation Flux Switching Machine

Research and development on hybrid excitation flux switching machines (HEFSM) for various applications have been carried out in the last years. The designed HEFSM consist of permanent magnet (PM) and DC field excitation coil (DC-FEC) which is located on the stator core as their main flux sources, while a single piece rotor gives the advantages of robust rotor structure. Since most of the designed HEFSMs utilize three-phase windings, more complicated design and control system are required to run the motor. Thus, a new design of single-phase E-Core HEFSM with several advantages of much simpler converter size and smaller battery package due to small voltage capacity when compared with conventional three-phase system is proposed. Consequently, the size of overall configuration systems will also be reduced resulting in reducing total weight and cost. In this paper, initial performances of 4S-4P, 4S-6P, 4S-8P and 4S-10P E-Core HEFSM topologies are analysed. Since 4S-10P design gives highest torque and power performances, deterministic design optimization approach is conducted to enhance much higher and optimum performances. As conclusion, the optimized E-core HEFSM with 4S-10P topology has achieved maximum torque and power of 208.857Nm and 47.31 kW, respectively.

Investigation of a New Topology of Hybrid-Excited Flux-Switching Machine with Static Global Winding: Experiments and Modeling

This paper presents a new structure for a hybrid excitation, flux-switching synchronous machine. The particularity of this machine is its global excitation winding component that creates a three-dimensional (3-D) excitation flux path to control the global air gap flux. Both 3-D finite-element analysis and a comparison with experimental results are provided. This model makes it possible to: show the excitation flux path, explore the flux-regulation capability of a new structure, and identify the influence of material characteristics. The experimental performance of this machine in a dc generator is presented and compared with simulation output.

Performance Comparison and Analysis of (HEFSM) and (FEFSM) Using Segmental Rotor Structure

This paper presents a new structure of hybrid excitation flux switching motor (HEFSM) using segmental rotor and the comparison of HEFSM and FEFSM using segmental rotor is performed to find the best candidate for hybrid electric vehicles (HEV). (HEFSM) using segmental rotor contains both the FEC and PM on the stator to produce maximum flux linkages. Initially, the coil arrangement tests are examined to validate the operating principle of the (HEFSM) using segmental rotor. Moreover the profile of flux linkage, cogging torque, and torque characteristics at various armature current densities of both the (HEFSM) and (FEFSM) using segmental rotor are observed based on 2D-finite element analysis (FEA). Initially performances show that HEFSM using segmental rotor produces torque of 18 Nm with low cogging torque and sinusoidal flux waveform. Thus by further design optimization the proposed motor will effectively achieve the target performances.

Design Optimization of Single-Phase Outer-Rotor 8S-8P Hybrid Excitation Flux Switching Motor for Electric Vehicle

Nowadays, in-wheel motors applied in pure electric vehicles (EVs) propulsion systems have attracted great attention in advance research and development. In-wheel direct drive provides quick torque response, higher efficiency, weight reduction, and increased vehicle space. As one of alternative, a new design of outer-rotor hybrid excitation flux switching motor (ORHEFSM) for in-wheel drive EV is proposed. In this paper, the optimization design of single-phase 8S-8P outer rotor HEFSM is analysed. Open and close circuit of initial and final design is compared based on 2-D finite element analysis (FEA). The design optimization has been made on the initial design machine shows that there is great enhancement on torque and power.

Optimization of 6S-14P E-Core Hybrid Excitation Flux Switching Motor for Hybrid Electric Vehicle

Research on hybrid electric vehicle (HEV) which combined battery based electric motor and conventional internal combustion engine (ICE) have been intensively increased since the last decade due to their promising solution that can reduce global warming. Some examples of electric motors designed for HEV propulsion system at present are dc motor, induction motor (IM), interior permanent magnet synchronous motor (IPMSM) and switched reluctance motor (SRM). Although IPMSMs are considered to be one of the successful electric motor used in HEVs, several limitations such as distributed armature windings, un-control permanent magnet (PM) flux and higher rotor mechanical stress should be resolved. In this paper, design improvement of E-Core hybrid excitation flux switching motor (HEFSM) for hybrid electric vehicles (HEVs) applications are presented. With concentrated armature and field excitation coil (FEC) windings, variable flux capability and robust rotor structure, performances of initial and improved 6S-14PE-Core HEFSM are analyzed. The improved topology has achieved highest torque and power of 246.557Nm and 187.302 kW, respectively.

Analysis of Two Novel Five-Phase Hybrid-Excitation Flux-Switching Machines for Electric Vehicles

In this paper, two five-phase hybrid-excitation flux-switching (HEFS) machines with different stator topologies are designed and analyzed with the identical stator outer diameters and stack lengths. The electromagnetic performances, including the conventional static characteristics, such as phase flux, back-EMF, inductance, cogging torque and electromagnetic torque, and so on, are presented first. Then, both the flux-strengthening and flux-weakening capabilities are evaluated in detail according to the electromagnetic torque characteristics under different field currents with the help of 2-D finite element analysis. The corresponding predictions and conclusions indicate that the U-core topology is preferred for the five-phase HEFS machines.

Design optimisation of an axial flux‐switching hybrid excitation synchronous machine at no‐load

This paper presents an optimization analysis of an axial flux-switching hybrid excitation synchronous machine (AFHESM) to improve its no-load electromagnetic performances. The shapes of permanent magnet (PM), rotor-teeth and stator slot of AFHESM are investigated for a better design scheme by finite element analysis (FEA). Some optimal results under no-load are achieved, which mainly including the induced electromotive force (EMF), cogging torque and field control ability. Both FEA and experimental results show that the induced EMF can be improved when PM shape coefficient is 0.95 and the rotor-teeth bevel angle is 6°.

Excitation Winding Short-Circuits in Hybrid Excitation Permanent Magnet Motor

This paper presents two short-circuit fault models of a hybrid excitation flux switching permanent magnet machine, i.e., excitation phase short-circuit and interturn short-circuit in excitation windings. Two-dimensional finite element (FE) method is used to calculate the major parameters, such as armature and excitation inductances, which are not only functions of rotor position, but also of armature and excitation currents. Moreover, in case of short-circuits, the variations of armature and excitation currents are often significant. This in turn leads to an important change in winding inductances. Therefore, in order to precisely predict machine performance under short-circuit conditions, the use of inductances versus rotor position and RMS currents is essential. With the obtained FE results, two MATLAB/Simulink-based models are established. Then, the previously mentioned short-circuits have been studied and their influences on electromagnetic performances, such as armature and excitation currents, speed and torque, armature and excitation copper losses, stator and rotor core iron losses, as well as permanent magnet (PM) eddy current losses are analyzed. Experiments have been carried out to validate the simulations.

Analytical Design of Flux-Switching Hybrid Excitation Machine by a Nonlinear Magnetic Circuit Method

The flux-switching hybrid excitation machine is an interesting brushless machine with magnets and excitation windings in the stator. Due to the unique structure and hybrid excitation, the assignment for electric excitation and permanent magnet excitation becomes a difficult issue. To explore a rapid design method, the nonlinear magnetic circuit analytical model of the element machine has been developed, which introduces the technologies of critical regions subdivision and iterative solutions for magnetic permeability into the magnetic circuit model. Then, the ampere turns of electric excitation, the recommended value of initial magnetic bridge flux density, the influence of stator yoke thickness on magnet dimensions and field regulating coefficient are also included. Finally, the finite element analysis and the experimental results are presented. The proposed method is not only reasonable and effective but also efficient, which provides a reference for the flux-switching hybrid excitation machine (FSHM) design and performance analysis.