Shen Jiafeng

Study on three-phase four-leg control technology of permanent magnet synchronous motor in electric vehicle

The permanent magnet synchronous motor (PMSM) has many advantages, such as high energy density, high efficiency and high power factor, and its application in electric vehicle is rapidly expanding. The traditional main circuit structure of three-phase three-leg topology with the space-voltage vector pulse width modulation (SVPWM) technology can reduce the winding harmonic currents and meanwhile improve the utilization rate of the DC voltage, thus reduce the torque ripple of the motor and broaden the speed range of motor effectively. However, in a-phase fault, the system reliability will be difficult to be maintained by the traditional topology structure. Therefore, it is limited on some occasions where reliability is strictly required, such as highway traffic, aviation, marine and explosion-proof, etc. On this basis the paper puts forward a three-phase four-leg control system with the fault-tolerant function. Namely, on the basis of traditional three-phase four-leg control system, the fourth leg is added and connected to the motor neutral point, and three dimensional voltage space vector modulation (3D-SVPWM) technique is utilized to drive PMSM, which make PMSM has a good running characteristics and can guarantee system safe and reliable running in the case of the lacking phase or the one-phased open-circuit fault, and in the aspect of electric vehicle drive has higher application value.

Analysis of the influence of rotor material on IMCCR temperature field

A new kind of induction motor with compound cage rotor(IMCCR) is developed in this paper, in which rotor bar is composed of upper part made of alloy material (conductor of electric and magnetic) and lower part made of cast aluminum. Firstly, the calculating models of the machinepsilas electromagnetic field and whole region(include stator and rotor) temperature field were established and some losses were obtained through analyzing electromagnetic field of IMCCR by using finite element method(FEM), which taken as the heat souse of temperature fields. Thus the unidirectional electro-thermal weak coupling analysis was achieved. Then, by changing the heat conductivities of the rotor alloy cage, its influence on motor temperature distribution was analyzed, and some references for rotor material study could be obtained.

The heat conducting analysis of transient temperature field in IMCCR with discontinuous blocked rotor under different structure

A new kind of induction motor with compound cage rotor(IMCCR) is developed in this paper, in which rotor bar is composed of upper part made of alloy material (conductor of electric and magnetic) and lower part made of cast aluminum. The transient heat conducting process of IMCCR running with discontinuous blocked rotor was studied, in which two different structure rotors were compared analyzed. The transient temperature field was numerically calculated by using the method of coupling electromagnetic field and temperature field, in which the continuous process with application of full voltage during 10s rotor locked, natural cooling during 600s disconnection of motor and during repeated next 10s rotor blocked is simulated. Based on the above, this paper presented the heat conducting process of the stator equivalent windings and change trend of bidirectional heat conducting of parts of stator. Then radial transient heat conducting processes of rotor when blocked and natural cooling were analyzed. At last, the influence of different material conductivity on the temperature distribution near the inner circle of stator was explored, in which the calculated values at the measured points were compared with the tested ones.