Ping Zheng

Optimization of the Magnetic Pole Shape of a Permanent-Magnet Synchronous Motor

A kind of six-slot/four-pole permanent-magnet (PM) synchronous motor is very popular nowadays for the advantages of saving coppers and because it is easy to manufacture. The magnetomotive force (MMF) produced by the six-slot stator windings are not symmetrical under the four poles, and more harmonics exist in the air gap, which will increase the torque ripple and noise. In this paper the rotor structure is optimized from the aspects of magnetic-pole embrace, magnetic bridge, and magnetic-pole eccentricity to obtain better air-gap magnetic field distribution and torque curves

Research on the High Power Density Electromagnetic Propeller

With the rigorous requirements of high power density, high efficiency, and low noise for propulsion system in many fields, an electromagnetic propeller tends to replace the traditional heat engine propeller. A permanent-magnet synchronous motor used for the electromagnetic propeller is investigated in this paper. The electromagnetic and thermal fields are analyzed with the finite-element method. The influences of different water flow parameters on the winding and permanent-magnet temperatures are discussed and the water cooling system is designed. The power density of approximately 4.18 kW/kg can be obtained for the investigated motor through the electromagnetic and thermal analysis

Investigation of the winding current distribution in a 4-quadrant-transducer prototype machine

The 4-quadrant energy transducer (4QT) is a solution to realize both the torque and speed control of the internal combustion engine (ICE) for hybrid electric vehicles. Since the base frequency of the prototype 4QT is much higher than the industrial one, the effect of eddy current on winding current distribution is considered in this paper. A two-dimensional (2-D) eddy-current FEM model is established and used for analysis. Current density and strand current distribution are given. It is pointed out that owing to the effect of eddy current, the conductor currents are unevenly distributed within the strands of the same turn. According to the 2-D FEM analysis, when the uneven current distribution is considered, the average rms turn current is increased by 1.05 times for the stator and 1.65 times for the inner rotor, and the copper loss is increased by 1.1 times for the stator and 3.16 times for the inner rotor. Since the inner rotor slots are much deeper than the stator slots, the inner rotor current distribution is more uneven than the stator. It means that for high-frequency deep-slot machine the eddy current effect should be considered seriously. Because of the increased current and copper loss, more ventilation will be needed for the 4QT, especially for the inner rotor. The average torques of stator machine and double rotor machine meet the requirements, and the torque ripples are small owing to the skewed slots.

Widely developing electric launch technology in China

It can be seen from the 20 abstracts submitted to the 11th Electromagnetic Launch (EML) Technology Symposium by five Chinese departments, that China is developing extensive electric launch technology. At least four Chinese ministries support the experimental research on electrothermal launch technology, electromagnetic rail launch technology, coil launch technology, and reconnection launch technology, respectively. There is also research being done on the electric armor and electromagnetic pumping technologies that are correlative with the electric launch technology. Some other ministries have established various foundations to support the theoretical research on electric launches. In addition, international cooperation in science and technology is under way. For example, we are currently doing cooperative experimental research on the electromagnetic launch with some foreign experts, and coauthoring a book titled Physics of Electric Launch (English version). China emphasizes the cultivation of successors on the electric launch technology. Since the first Peter Kemmy Memorial Student Scholarship was awarded to a Chinese young scholar in 1998, more universities have begun to offer courses in electric launch technology for undergraduates as well as for Masters and Ph.D. degree students. Furthermore, some postdoctoral researchers are researching electric launch technology in their theses. To organize and unite national researchers on electric launch technology, encourage more people to enter the field, and stimulate further development, recently we have initiated to establish the China Electromagnetic Launch Society. The establishment of the Society makes it convenient for us to accept the lead of the international EML Permanent Committee, and to offer an opportunity of academic exchange and cooperation from home and abroad.

Influence of saturation and saliency on the inductance of a four-quadrant transducer prototype machine

An inductance determination method that can be based on both experiments and calculations is discussed in this paper. The inductances of a four-quadrant transducer (4QT) prototype machine were measured and calculated with the two-dimensional time-stepping finite-element method (FEM), and the measured and calculated results are in good agreement. It is found that the d- and q-axis inductances are different, and the inductances obtained from the phase and line voltage are also different for both the two machines of the 4QT prototype machine. Analysis shows that the differences are caused by the saliency and d-axis saturation. Although there is little saliency for the double rotor machine (DRM), the two kinds of the inductance differences of the DRM are more serious than that of the stator machine (SM). This is because of the higher level of the d-axis saturation of the DRM. The inductances obtained from the phase voltage at very low frequency are recommended as final results for both experiments and calculations

Finite-element analysis for the active electromagnetic armor projectile interceptor

Along with the continuous development of the intellectualized antitank ammunition and the application of the future electric gun in the battlefield, the armored vehicles encounter an increasingly heavy threat in the battlefield. So the armor protection has to develop new technologies so as to enhance the armored vehicles survivability in the battlefield. A new concept practical application of the pulsed power technology-active electromagnetic (EM) armor was discussed in this paper. It combined the intellectual fire-control, advanced detector, and precise EM projectile interceptor. It must be the developing direction of the active protection system. A structural and mathematical model of the active EM armor projectile interceptor based on the principle of single stage coil launcher is given in this paper. It analyzes the effects of the electric parameter in the discharge circuits and the structural property of the interceptor to the launching velocity and efficiency of the interceptor. Finally the model is simulated numerically by finite-element analyses.

Research on the passive electromagnetic armor

The three-dimensional finite-element method (3-D FEM) model of the passive electromagnetic (EM) armor is established. The passive EM armor is analyzed with 3-D magnetostatic field. The magnetic field and ampere force distribution on various cross sections and the total force acting on the projectile are given. The force calculated by 3-D FEM is almost the same as that obtained by analytical method. The dynamic principle of the projectile is analyzed.

Research on a tubular yokeless PM linear machine

Free-piston energy converter, which has great potential in applications of space and electric vehicles (EVs), has drawn wide interests in recent years. Free-piston energy converter consists of a free-piston Stiring engine and a linear machine. Tubular permanent-magnet (PM) linear machines are widely adopted due to the salient characteristics like high power density and high efficiency. Radially-magnetized, axially-magnetized, and quasi-Halbach PM linear machines are developed [1-3]. However, the common demerit of the developed machines is the low utilization of space, which provides potential for the improvement of power density. Hence, a novel yokeless PM linear machine is reported in this paper. Compared with conventional PM linear machines, the proposed machine has advantages of higher power density, higher efficiency, and higher utilization of space.

Magnetic circuit analysis and performance improvement of a tubular staggered-tooth transverse-flux linear machine for free-piston energy converter

A free-piston energy converter (FPEC) integrated by a combustion engine and a linear electric machine is suitable for series HEV or other applications stand-alone generators . The transverse-flux machine (TFM) is considered advantageous for such application because of its high specific power and force density. The finite element method (FEM) is widely used in the machine analysis, which is time-consuming . The equivalent magnetic circuit analysis is a time-effective method compared with FEM. In this paper, a tubular staggered-tooth transverse-flux permanent magnet (PM) linear synchronous machine (STTF-PMLSM) is proposed, which is used for FPEC. The machine is characterized by a relative high power factor due to the low flux leakage. An equivalent magnetic circuit model of the machine has been proposed . The magnetic circuit analysis results are validated by the results of 3-D FEM simulation. The influence of leading design parameters, mainly containing PM magnetization length (hm), pole pitch (p) and length of the stator core (ls), on the performance of machine is analyzed in detail.

Research on the magnetization of a tangentially magnetized brushless DC motor

For the permanent magnets used in a tangentially magnetized brushless DC motor, normally they can be magnetized by three ways: component magnetization, sub-assembly magnetization and post-assembly magnetization. In this paper the post-assembly magnetization is investigated and compared with the component magnetization. After two times of post-assembly magnetization, the permanent magnets in the tangentially magnetized brushless DC motor can be fully magnetized. The rotor surface flux densities and motor performance curves of component magnetization and post-assembly magnetization are consistent.