Quanbin Zhao

Investigation of a Novel Radial Magnetic-Field-Modulated Brushless Double-Rotor Machine Used for HEVs

A novel brushless compound-structure permanent-magnet synchronous machine (CS-PMSM) with six different topologies is proposed based on the magnetic field modulation principle. As the key part of the brushless CS-PMSM, the radial magnetic-field-modulated brushless double-rotor machine (MFM-BDRM) is investigated on the speed and torque relations of the first-stator magnetic field, the first-PM rotor and the modulating ring rotor by analytical method. Besides, on the basis of analyses of magnetic field distribution in the inner and outer air gap, the back electromagnetic force and torque performance of the radial MFM-BDRM are further studied by finite-element method (FEM). The results indicate that the low power factor is a major problem of the radial MFM-BDRM. Therefore, the influence of parameters, such as combinations of magnetic block number and PM pole pair number, the span ratio and radial thickness of magnetic blocks, and the length of air gap, on the power factor is analyzed. Additionally, to investigate the distribution law of core loss in the radial MFM-BDRM, amplitudes and frequencies of the magnetic fields in each part of the machine are analyzed. Furthermore, considering the weak mechanical strength of modulating ring rotor employing DW310 laminations, an attempt to use iron instead of DW310 in modulating ring rotor is investigated.

Characteristic Analysis and Verification of the Magnetic-Field-Modulated Brushless Double-Rotor Machine

The magnetic-field-modulated brushless double-rotor machine (MFM-BDRM), composed of the stator, the modulating ring rotor, and the permanent-magnet (PM) rotor, is a new power-split device for hybrid electric vehicles (HEVs). Compared with traditional double-rotor machines (DRMs), the MFM-BDRM shows more complicated electromechanical energy conversion relations, due to its special operating principle-the magnetic field modulation principle. To analyze the speed relation in the MFM-BDRM, a diagrammatized method is proposed. It shows that the speeds of stator magnetic field, modulating ring rotor, and PM rotor present a collinear speed characteristic. On this basis, the torque relations of stator, modulating ring rotor, and PM rotor are investigated from the view of a conservative lossless system. Then, a lever-balanced torque map is proposed to analyze their torque characteristic. It shows that the torques of stator, modulating ring rotor, and PM rotor can be calculated by the lever balance principle. The power flow map is further proposed to analyze the power flow characteristic among three ports. In addition, comparison of the MFM-BDRM and the planetary gear shows that the MFM-BDRM can be totally equivalent to an electrical machine and a planetary gear, making it gain a great advantage particularly when the MFM-BDRM is used in HEVs. The electromagnetic performance of MFM-BDRM is investigated by a finite-element method, which shows that the MFM-BDRM has advantages of fine sinusoidal back electromotive force and low torque fluctuation. Finally, the speed and torque analysis and FE results are verified by experiment.

A Brushless Claw-Pole Double-Rotor Machine for Power-Split Hybrid Electric Vehicles

This paper investigates a claw-pole double-rotor machine (DRM) for power-split hybrid electric vehicles (HEVs). Based on the mathematical analysis of the machine, the boundary speed-torque characteristic required by the hybrid electric system is studied. To achieve high power density with acceptable torque ripple for automotive applications, the back electromotive force (EMF) and torque performance of the DRM are investigated with respect to the configurations of permanent-magnet rotor, claw-pole dimensions, and air-gap length. Based on the optimized model, characteristics of the claw-pole DRM, such as flux density, inductance, torque, core losses, and efficiency, are investigated by finite-element method. A downsized prototype machine is manufactured and tested. The experimental EMF, inductance, and torque performance agree well with simulation data. A drive cycle containing various working modes of the DRM is carried out, and the feasibility of using the machine as a power-split device for HEVs is validated.

Research on electromagnetic performance of an axial magnetic-field-modulated brushless double-rotor machine for hybrid electric vehicles

This paper proposes an axial magnetic-field-modulated brushless double-rotor machine (MFM-BDRM), which is suitable for application in hybrid electric vehicles (HEVs). As the axial MFM-BDRM has dual mechanical ports, two connection ways of the machine in HEV system are evaluated, and the better connection way is selected based on power comparison. Speed decoupling characteristic and operation modes of the axial MFM-BDRM as generator, magnetic gear and motor are discussed. Electromagnetic performance of three operation modes, viz. the waveforms of no-load back electromotive force (EMF), torque transmission capability, torque ripple and power factor, is investigated. The above analyses are simulated with three-dimensional (3-D) finite-element method (FEM).

Magnetic circuit and torque analysis of a brushless transverse flux dual-rotor machine used for HEVs

The paper proposes a new compound-structure transverse flux permanent-magnet synchronous machine (CS-TFPMSM) system to fulfill power split for hybrid electric vehicles (HEVs). The key component of this system is one brushless transverse flux dual-rotor machine (TFDRM) which originates from transverse flux machines. The TFDRM can realize speed adjustment and torque transfer. The structure and operation principle are first introduced. The magnetic flux path and its characteristics are then described. The magnetic circuit model of the proposed TFDRM is also developed. Based on the magnetic circuit analysis, the expressions for d-, q-axis magnetic flux and electromagnetic torque are deduced. The 3D finite element method (FEM) is used to simulate the impact of main parameters on the torque. The methods to obtain high average torque and reduce torque ripple are finally discussed.

An axial magnetic-field-modulated brushless double-rotor machine for hybrid electric vehicles

This paper proposes an axial magnetic-field-modulated brushless double-rotor machine (MFM-BDRM) for hybrid electric vehicles (HEVs), which can realize the function of speed decoupling. Without brushes and slip rings, it has significant advantages such as low maintenance and high heat dissipation capacity. In this paper, topology and operating principle of the machine are investigated. As the axial MFM-BDRM is simulated with 3-dimensional finite element method, the electromagnetic calculation model is simplified to save calculating time. Moreover, the principle of simplification is summarized. After that, due to the poor power factor of the machine, parameters that influence the power factor are analyzed with simplified model.

Torque ripple reduction in an interior permanent-magnet synchronous motor for servo applications

An interior permanent-magnet synchronous motor (IPMSM) used for high-performance industrial servo applications is investigated. Compared with surface mounted PMSM, the IPMSM features simple fixing of permanent magnets. However, torque ripple reduction is still an important issue. Three rotor structures are comparatively studied by the finite-element method (FEM) in this paper. The optimizations of rotor eccentricity for models of 48-slot/8-pole, 36-slot/8-pole and 18-slot/8-pole are investigated, respectively. Moreover, the influences of the permanent magnet (PM) width, the PM slot span angle and the width of slot notch on torque ripple are also discussed.

Scheme optimization of an axial magnetic-field-modulated brushless double-rotor machine

The magnetic-field-modulated brushless doublerotor machine (MFM-BDRM) system, mainly consisting of the MFM-BDRM and a conventional permanent magnet synchronous machine, is a novel power-split concept to realize both the speed and the torque control of the internal combustion engine (ICE) for hybrid electric vehicles (HEVs). Without brushes and slip rings, the system has significant potential advantages such as low maintenance and high heat dissipation capacity. As a key part of the MFM-BDRM system, an axial MFM-BDRM is investigated in this paper. As the axial MFM-BDRM realizes stable torque transmission based on the effective harmonic magnetic field, modulation effect of the machine is discussed. In order to determine the scheme, electromagnetic performance is evaluated with models of different combination between the pole-pair number of the stator and that of the permanent magnet rotor. After that, the preferred scheme is optimized to improve the torque transmission capability. The above analyses are simulated with the three dimensional (3-D) finite-element method (FEM).

Research on the vibration and noise of less rare-earth interior U permanent magnet synchronous machine

In recent years, a lot of attentions have been paid to the less rare-earth permanent magnet synchronous machine (LRE-PMSM). The LRE-PMSM combines the features of two machine types: high energy density, high efficiency of the permanent magnet synchronous machine and the lower cost of the synchronous reluctance machine. The design optimization of the less rare-earth interior U permanent magnet synchronous machine (LRE-IUPMSM) is investigated in this paper. And a general approach for the analysis of noise is presented.

Torque density improvement of transverse-flux dual rotor machine for power-split hybrid electric vehicle application

A new brushless compound-structure transverse-flux permanent magnet synchronous machine (CS-TFPMSM) is proposed in this paper. It can help the hybrid electric vehicles (HEVs) to fulfill power split and adjust the torque and speed from the internal combustion engine (ICE). As the key component of the CS-TFPMSM, the transverse-flux dual rotor machine (TFDRM) originates from the transverse-flux machine (TFM). The TFDRM can keep the principle of TFM unchanged, and fulfill the elimination of brushes. The operation principle is described; and the expression for the torque density is deduced. Based on that, the characteristics of the TFDRM are investigated. Because of the three-dimensional (3D) complicated magnetic circuit, the 3D finite element method (FEM) is used to simulate the performances of the TFDRM. The influences of main geometry parameters, such as the pole-pair number, the length of the outer/inner air gap, the sizes of the permanent magnets, and so on, on the torque density are simulated with the 3D FEM. The methods to enhance the torque density are discussed.