A graphic monitoring method for electric power of VVVF hydraulic system

In order to online monitor the running state of variable voltage and variable frequency(VVVF)hydraulic system,this paper presents a graphic monitoring method that fuses the information of variable frequency electric parameters.This paper first analyzes how the voltage and current of the motor stator change with the operation conditions of VVVF hydraulic system.As a result,we draw the relationship between the electric parameters(voltage and current)and power frequency.Then,the signals of the voltage and current are fused as dynamic figures based on the idea of Lissajous figures,and the values of the electric parameters are related to the features of the dynamic figures.Rigorous theoretical analysis establishes the function between the electric power of the variable frequency motor(VFM)and the features of the plotted dynamic figures including area of diagram,area of bounding rectangle,tilt angle,etc.Finally,the effectiveness of the proposed method is verified by two cases,in which the speed of VFM and the load of VVVF hydraulic system are changed.The results show that the increase of the speed of VFM enhances its three-phase electric power,but reduces the tilt angle of the plotted dynamic figures.In addition,as the load of VVVF hydraulic system is increased,the three-phase electric power of VFM and the tilt angle of the plotted dynamic figures are both increased.This paper provides a new way to online monitor the running state of VVVF hydraulic system.

DBD电路模型参数的测量与仿真分析

为了能够对介质阻挡放电(Dielectric Barrier Discharge,DBD)的物理机制有更深入的理解,目前国内外许多学者采用电路模型仿真与实验相结合的方法来对介质阻挡放电进行研究,它们通过结合实际的试验条件,提出了许多不同的电路仿真模型。本文在华中科技大学张庭提出的电路模型基础之上,通过实验和理论计算分别得到了试验装置的介质电容和气隙电容,对该模型进行了仿真,并对仿真结果和试验结果进行了比较。在保持电感L和电源频率f及幅值不变的情况下,讨论了当记忆电阻Rmen和记忆电容Cmen变化时,放电电流从单峰模式向多峰模式的演变规律。并对电流脉冲的变化情况与记忆电阻和记忆电容的关系进行了探讨,以期能够对DBD的放电机理有更深入的理解。