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Due to inclement weather in recent years, the short-circuit fault cannot be ruled out in a short time on power system, and this make the transformer as the main components of the system will withstand the impact of two consecutive short-circuit current in a short time, which makes the winding disks in the initial short circuit without damage, its residual deformation and vibration situation can meet...
The widely developed and used HVDC transmission systems will cause DC bias phenomenon occurred in some electromagnetic facilities of power grids with the results of several negative effects on the secure and reliable operation, including vibrations and noises. However, there has been few studies regarding the influence DC bias has on shunt reactors. To fully explore the vibration characteristic of...
This paper reports a packaged energy harvester using the novel method of micro-molding bulk electrets of polytetrafluoroethylene (PTFE). Compared with thin film electrets prepared by spin-coating method, bulk PTFE electrets are of higher trapped charge density by 1.2∼2 times, and improved charge storage stability by 1.3 times in charge retain rate over 10 days. Further, the micromolding method guarantees...
In order to further investigate the vibration performance of power transformer for the detection of winding deformation based on the vibration frequency response analysis (VFRA) method, the electro dynamic forces of the winding of power transformer are calculated first by virtue of the field-circuit coupled finite element method. Then the axial vibration model of the winding is built and the harmonic...
In the paper, a variable frequency constant current power supply is developed to provide the variable frequency current to vibrate the power transformer. A proportional resonant controller is applied to control the current constant. The designed experiment of vibration frequency response analysis for the 220kV transformer is made to validate the effective of the power supply. Experimental results...
Chaos anti-control is considered for mechanical vibration control. The linear system under period excitation is guided to a chaotic system by a traditional control method. After the dynamic equation of the system is transferred to a dimensionless one, it was made to track Duffing system by adding a controller. The control parameters were selected according to Mélnikov criterion instead of calculation...
In order to further recognize the relationship between the fault of winding deformation of power transformer with the measured tank vibration, the short-circuit test is done in a 220kV transformer. The vibration sweep frequency response curves for some pre-setting winding deformation fault are obtained by virtue of the vibration measurement system. Correlation coefficient is defined and calculated...
This study calculated the stresses and deformations of the acrylic tanks used in neutrino experiment under dynamic loads and evaluated the safety level of those tanks. The diameters of those large t tanks are ??3m and the thickness of their walls are only 10mm. The measured mechanical properties are: EB=2.95GPa ??8%, SY=77.92 ??7%, SU= 102.13MPa ??12%. The stress distributions of the tanks were simulated...
An electromagnetic self-powered vibration energy scavenger is developed, which can convert low-level vibrational energy into electrical energy. It consists of a magnet-spring system and a two-layer copper coil. The nickel planar spring and the two-layer copper coil are fabricated using UV-LIGA technology and microelectroplating technology. Testing results show that the fabricated vibration energy...
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