The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature...The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature such as wind loading. This imposes a periodic force on the conductors which is highly undesirable. It is therefore important for engineers to account for the possible effect of the wind loading when designing the power line. Investigations have shown that modeling the exact dynamic behaviour of a conductor is very difficult. Based on this fact, getting the exact analytical solution to conductor vibration is difficult, which is almost impossible, hence the numerical approximation becomes an option. This paper presents the developed finite element method used to analyse the dynamic behaviour of transmission line conductors. The developed FEM （finite element method） is implemented on MATLAB. The numerical analysis using MATLAB that is presented in this paper is used to simulate the response of the conductor when subjected to external loading in the time domain. The simulation is used to analyse the transverse vibration of the conductor. The formulation of the stiffness matrix and load vector is done and the results obtained are used to evaluate the conductor＇s internal energy dissipation. This finite element solution is compared with the results documented in literature. This numerical simulation is also used to investigate the effects of varying the axial tension on energy dissipation within the strands. Hence, this evolved in physically appropriate energy characterization process that can be used to evaluate the conductor self-damping with respect to line contact.展开更多
A major source of electric vehicle energy loss is the vibration energy dissipated by the shock absorbers under irregular road excitation,which is particularly severe when active wheel systems are employed because thei...A major source of electric vehicle energy loss is the vibration energy dissipated by the shock absorbers under irregular road excitation,which is particularly severe when active wheel systems are employed because their greater unsprung mass leads to greater shocks and vibrations.Therefore,a tubular linear energy harvester(TLEH)with a large stroke and low electromagnetic force ripple is designed to convert this vibration energy into electricity.The proposed TLEH employs a slotted external mover with three-phase winding coils and an internal stator with PMs to increase the stroke,adopts a fractional slot-per-pole configuration to reduce its size and improve the winding factor,and realizes significantly reduced cogging force by optimizing the incremental length of the armature core.A finite element model of the TLEH is first verified against a theoretical model and then used to investigate the influences of various road excitation frequencies and amplitudes on the electromotive force(EMF)waveforms and generated power,the efficiency and damping force according to load condition,and the energy recovery and nonlinear electromagnetic force characteristics of the TLEH.A resistance controller is then designed to realize a self-damping electromagnetic suspension.The results indicate that the EMF and the generated power waveforms depend on the excitation frequency and amplitude,the efficiency increases and the damping coefficient decreases with the increasing load resistance.展开更多
文摘The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature such as wind loading. This imposes a periodic force on the conductors which is highly undesirable. It is therefore important for engineers to account for the possible effect of the wind loading when designing the power line. Investigations have shown that modeling the exact dynamic behaviour of a conductor is very difficult. Based on this fact, getting the exact analytical solution to conductor vibration is difficult, which is almost impossible, hence the numerical approximation becomes an option. This paper presents the developed finite element method used to analyse the dynamic behaviour of transmission line conductors. The developed FEM （finite element method） is implemented on MATLAB. The numerical analysis using MATLAB that is presented in this paper is used to simulate the response of the conductor when subjected to external loading in the time domain. The simulation is used to analyse the transverse vibration of the conductor. The formulation of the stiffness matrix and load vector is done and the results obtained are used to evaluate the conductor＇s internal energy dissipation. This finite element solution is compared with the results documented in literature. This numerical simulation is also used to investigate the effects of varying the axial tension on energy dissipation within the strands. Hence, this evolved in physically appropriate energy characterization process that can be used to evaluate the conductor self-damping with respect to line contact.
文摘A major source of electric vehicle energy loss is the vibration energy dissipated by the shock absorbers under irregular road excitation,which is particularly severe when active wheel systems are employed because their greater unsprung mass leads to greater shocks and vibrations.Therefore,a tubular linear energy harvester(TLEH)with a large stroke and low electromagnetic force ripple is designed to convert this vibration energy into electricity.The proposed TLEH employs a slotted external mover with three-phase winding coils and an internal stator with PMs to increase the stroke,adopts a fractional slot-per-pole configuration to reduce its size and improve the winding factor,and realizes significantly reduced cogging force by optimizing the incremental length of the armature core.A finite element model of the TLEH is first verified against a theoretical model and then used to investigate the influences of various road excitation frequencies and amplitudes on the electromotive force(EMF)waveforms and generated power,the efficiency and damping force according to load condition,and the energy recovery and nonlinear electromagnetic force characteristics of the TLEH.A resistance controller is then designed to realize a self-damping electromagnetic suspension.The results indicate that the EMF and the generated power waveforms depend on the excitation frequency and amplitude,the efficiency increases and the damping coefficient decreases with the increasing load resistance.
