Zhang Yihuang

A direct field-circuit-motion coupled modeling of switched reluctance motor

A direct field-circuit-motion coupled model combined with finite-element analysis is presented to simulate the steady operating state of switched reluctance motors and to calculate the dynamic currents and torques of the motors. The related control strategies of driving system could be implemented easily using this model, and various phase windings energized operating states could be analyzed accounting for material nonlinearities and the effects of mutual coupling between motor phases. The model is used to study normal operating state and a fault operating state with one branch of a phase winding broken. The comparison and analysis of the numerical and measured results indicates the validity of the model and method proposed in this paper.

Influence of Copper Screen Thickness on Three-Dimensional Electromagnetic Field and Eddy Current Losses of Metal Parts in End Region of Large Water-Hydrogen–Hydrogen-Cooled Turbogenerator

Aiming at the complexity of the structure in the end region of large turbogenerators, 3-D mathematical and physical models of nonlinear transient eddy current field are given by taking a 330-MW water-hydrogen-hydrogen-cooled turbogenerator for example. Both nonlinearity of B-H curve and noncontact structure between the copper screen and press plate, as well as the evolvent of stator end windings, were taken into consideration. When the copper screen thickness is different in the end region of the generator, 3-D transient electromagnetic field and losses of metal parts were calculated under no-load and rated-load conditions by finite-element method. The metal part losses, which were obtained from transient electromagnetic field, were applied to the thermal field as heat sources. Temperatures of copper screen were gained after the thermal field was calculated in the end region. The calculated results coincide well with the measured data.Aiming at the complexity of the structure in the end region of large turbogenerators, 3-D mathematical and physical models of nonlinear transient eddy current field are given by taking a 330-MW water-hydrogen-hydrogen-cooled turbogenerator for example. Both nonlinearity of B-H curve and noncontact structure between the copper screen and press plate, as well as the evolvent of stator end windings, were taken into consideration. When the copper screen thickness is different in the end region of the generator, 3-D transient electromagnetic field and losses of metal parts were calculated under no-load and rated-load conditions by finite-element method. The metal part losses, which were obtained from transient electromagnetic field, were applied to the thermal field as heat sources. Temperatures of copper screen were gained after the thermal field was calculated in the end region. The calculated results coincide well with the measured data.

Nonlinear modeling of switched reluctance motor based on combination of neural network and genetic algorithm

Switched reluctance motor is very difficult to create a precise mathematic model for its nonlinear electromagnetism characteristic. But the optimal control of SRM needs an accurate mathematical model. Neural network has the ability of self-learning and can approach the result with any accuracy. However neural networks ability of convergence and searching a global optimal solution is poor. Genetic algorithm is able to search for a global optimal solution in a short time, so an accurate result can be speedily obtained through combining neural network and genetic algorithm. In this article the method of construct a nonlinear modeling of SRM with the combination neural network and genetic algorithm is presented. The results of simulation show that through combining neural network and genetic algorithm the speed of convergence and the accurate of computation are improved. So it can be used in optimal control of SRM.

Field circuit coupled time stepping finite element analysis on permanent magnet brushless DC motors

A time-segment circuit and field coupled time stepping FEA model is put forward in this paper, which is very suitable to analyze the permanent magnet brushless DC (BLDC) motors. According to the operation states and modes the time segment circuit equations can be determined. Magnetic field equations are directly coupled with the circuit equations. The armature current and torque can be obtained directly through calculation. The element analysis about the coupling problem of circuit and field is studied. A prototype is research using above model. The calculation results show good accordance with the experimental results

Influence of the End Ventilation Structure Change on the Temperature Distribution in the End Region of Large Water–Hydrogen–Hydrogen Cooled Turbogenerator

Flow network was built according to the ventilation structural characteristics of a 330 MW large water-hydrogen-hydrogen cooled turbogenerator. The variation of the fan inlet velocities, and the flow rates and pressures (boundary conditions) of each end region outlet were obtained, respectively, with different air gap spacer heights and different shelter board widths between the long press fingers by flow network method, and the relative law was analyzed. In order to study the influence of the changed end ventilation structures on the temperature distribution of the end parts, 3-D transient electromagnetic field in the turbogenerator end was calculated, and the eddy current losses (heat sources) of the end parts were gained by the finite-element method. Meanwhile, the fluid and thermal mathematics and physical models of the end region were given. Using the finite-volume method, the influence of the changed end ventilation structures on the surface heat transfer coefficient and the temperature of end parts was researched. It shows that the proper changes in the air gap spacer height and shelter board width decrease the copper shield temperature and result in a reasonable temperature distribution in the end parts. It provides the useful reference for the further design of the large turbogenerators.

Influence of Copper Shield Structure on 3-D Electromagnetic Field, Fluid and Temperature Fields in End Region of Large Turbogenerator

A new kind of the copper shield structure called the empty solid copper shield structure (ESCSS) in the large turbogenerator is proposed in this paper. Based on the complex structure characteristics of a 330-MW water-hydrogen-hydrogen cooled turbogenerator, the flow network within a half of the generator is established, and the total flow rate, pressure, flow rates (boundary conditions) of the various ventilation ducts and the chambers in the generator are separately obtained after solving the equations of the flow network when the traditional copper shield structure and the ESCSS are adopted. The 3-D transient electromagnetic field of the generator end region is calculated by using the time-stepping FEM, and the electromagnetic loss distributions (heat sources) are determined separately. Then, the fluid and thermal analysis model for the whole end region is established. Through numerical calculating, the whole end region 3-D fluid and temperature distributions are obtained separately. The results show that the new copper shield structure makes the copper shield temperature much lower. Meanwhile, the copper shield material is saved. The obtained conclusions may provide useful reference for the optimal design and research of the large turbogenerator.

Simulation study of transverse flux linear switched reluctance drive

A transverse flux linear switched reluctance motor (TFLSRM) drive consisting of TFLSRM, speed and current controllers, commutation control, and position sensors, is proposed. Twelve primary side poles are composed of four sectors, and each sector includes three poles corresponding to three phases. Four windings of each phase, respectively located on four sectors, can be connected in series or parallel to achieve high efficiency for whole operating ranges. Each sector can operates in an independent manner, which means that the machine structure allows no simultaneous excitation of poles in different sectors, which enhances robustness of the system due to its fault tolerance capability. The elaborate optimum current waveform with assistance of current controller minimizes the thrust force ripple, meanwhile ensuring high efficiency. Speed control employs the nonlinear characteristic of thrust force to fulfil fast dynamic response. The mathematic models including electrical and mechanical dynamics are established. The parameters of TFLSRM model are obtained through digital computation of ANSYS-based magnetic field. On the basis of analyzing the structure and exciting feature of motor, the complete modeling and simulation, considering the nonlinear characteristic of the drive, are accomplished by using Matlab 6.5 software. The simulated results verify the proposed TFLSRM drive.

Influence of axial ventilation structures on electromagnetic field and heat transfer of traction motor used for high — Speed EMU

In order to fix the problems for high speed EMU that non-uniform temperature rise exist in axial and circumferential directions of asynchronous traction motor. We establish three dimensional solid models to analyze electromagnetic and fluid solid coupling filed of motor. And we make the comparison between numerical results of finite elements and experimental results. Based on that, we adjust circumferential distribution form and structure of axial vent of stator and rotor to research the relationship between the changes of key components inside the motor and temperature rise. By adjusting the incidence angle of fluid, we analysis the effect of fluid velocity to thermal performance of the motor. Through the above research we find the ventilation structure program which has balanced temperature distribution of axial and circumferential within the motor. And provide a reference strategy of temperature rise design of forced ventilation motor.

Influence of material doping degree on performance of IMCCR used for EV

At present, the total or main power energy in plug-in hybrid electrical vehicles and electrical vehicles is a limited energy source, and reducing the unnecessary loss effectively becomes one of the methods to enhance vehicle efficiency. In this paper, a kind of induction motor with compound cage rotor(IMCCR) is proposed, in which rotor bars are composed of upper parts made of alloy (conductor for electric and magnetic) and lower parts made of cast aluminum. By using FEM, starting performances of IMCCR is studied. From the comparison of obtained results with the test data, it can be inferred that IMCCR would be a better choice for driving system in vehicles. Considering the variation of alloy material characteristics caused by different materials components doping degrees, the influences of alloy bar materials on IMCCR flux distribution and machine performance are studied. Meanwhile, the effects special alloy bar positions and numbers on machine starting performance are researched. Some conclusions are summarized, which may provide useful reference for improving on driving induction motors used for vehicles.

Optimal-angle controller of switched reluctance motor based on EPROM

Since traditional angle position control of switched reluctance motor has an off-line calculation about turn-on and turn-off angle or a linear advance of angles with increasing speed and load, an on-line control scheme of angles is presented in this article, which optimize the steady-state performance of the drive as measured by torque per ampere. A method of realization of on-line control using EPROM is discussed in detail. Experimental results are provided to demonstrate the necessity and validity of the on-line control.