The simulation model of an unloading welding transformer was established on the basis of MATLAB software, and the modeling principle was described in detail in the paper. The model was made up of three sub models, i....The simulation model of an unloading welding transformer was established on the basis of MATLAB software, and the modeling principle was described in detail in the paper. The model was made up of three sub models, i.e. the linear inductor sub model, the non linear inductor sub model and series connection sub model controlled by current, and these sub models were jointed together by means of segmented linearization. The simulating results showed that, in the conditions of the high convert frequency and the large cross section of the magnet core of a welding transformer, the non linear inductor sub model can be substituted by a linear inductor sub model in the model; and the leakage reactance in the welding transformer is one of the main reasons of producing over current and over voltage in the inverter. The simulation results demonstrate that the over voltage produced by leakage reactance is nearly two times of the input voltage supplied to the transformer, and the lasting time of over voltage depends on time constant τ 1. With reducing of τ 1, the amplitude of the over current will increase, and the lasting time becomes shorter. Contrarily, with increasing of τ 1, the amplitude of the over current will decrease, and the lasting time becomes longer. The model has played the important role for the development of the inverter resistance welding machine.展开更多
The rocks surrounding a roadway exhibit some special and complex phenomena with increasing depth of excavation in underground engineering.Quasi-static analysis cannot adequately explain these engineering problems.The ...The rocks surrounding a roadway exhibit some special and complex phenomena with increasing depth of excavation in underground engineering.Quasi-static analysis cannot adequately explain these engineering problems.The computational model of a circular roadway considering the transient effect of excavation unloading is established for these problems.The time factor makes the solution of the problem difficult.Thus,the computational model is divided into a dynamic model and a static model.The Laplace integral transform and inverse transform are performed to solve the dynamic model and elasticity theory is used to analyze the static model.The results from an example show that circumferential stress increases and radial stress decreases with time.The stress difference becomes large gradually in this progress.The displacement increases with unloading time and decreases with the radial depth of surrounding rocks.It can be seen that the development trend of unloading and displacement is similar by comparing their rates.Finally,the results of ANSYS are used to verify the analytical solution.The contrast indicates that the laws of the two methods are basically in agreement.Thus,the analysis can provide a reference for further study.展开更多
文摘The simulation model of an unloading welding transformer was established on the basis of MATLAB software, and the modeling principle was described in detail in the paper. The model was made up of three sub models, i.e. the linear inductor sub model, the non linear inductor sub model and series connection sub model controlled by current, and these sub models were jointed together by means of segmented linearization. The simulating results showed that, in the conditions of the high convert frequency and the large cross section of the magnet core of a welding transformer, the non linear inductor sub model can be substituted by a linear inductor sub model in the model; and the leakage reactance in the welding transformer is one of the main reasons of producing over current and over voltage in the inverter. The simulation results demonstrate that the over voltage produced by leakage reactance is nearly two times of the input voltage supplied to the transformer, and the lasting time of over voltage depends on time constant τ 1. With reducing of τ 1, the amplitude of the over current will increase, and the lasting time becomes shorter. Contrarily, with increasing of τ 1, the amplitude of the over current will decrease, and the lasting time becomes longer. The model has played the important role for the development of the inverter resistance welding machine.
基金supported by the National Natural Science Foundation of China (Nos.51479108 and 51174196)the National Basic Research Program of China (No.2014CB046300)+1 种基金Shandong University of Science and Technology (No.2012KYTD104)Research Start-up Project of Shandong University of Science and Technology (No.2015RCJJ061)
文摘The rocks surrounding a roadway exhibit some special and complex phenomena with increasing depth of excavation in underground engineering.Quasi-static analysis cannot adequately explain these engineering problems.The computational model of a circular roadway considering the transient effect of excavation unloading is established for these problems.The time factor makes the solution of the problem difficult.Thus,the computational model is divided into a dynamic model and a static model.The Laplace integral transform and inverse transform are performed to solve the dynamic model and elasticity theory is used to analyze the static model.The results from an example show that circumferential stress increases and radial stress decreases with time.The stress difference becomes large gradually in this progress.The displacement increases with unloading time and decreases with the radial depth of surrounding rocks.It can be seen that the development trend of unloading and displacement is similar by comparing their rates.Finally,the results of ANSYS are used to verify the analytical solution.The contrast indicates that the laws of the two methods are basically in agreement.Thus,the analysis can provide a reference for further study.
