Performance analysis of the RC clampers in switching off no load arc furnace transformers
This paper presents an over-voltage attenuation performance analysis of RC clampers and surge arresters during transients caused by switching off a no load transformer applied to an arc furnace. A Brazilian Industry actual system was simulated using the Matlab/Simulink software. The simulation results indicate that the adequate use of RC clampers can reduce the arresters operations and practically eliminates the re-strikes and repetitive transient over-voltages when using vacuum circuit breakers to switch the arc furnace transformer.
Overvoltages due to switching off an unloaded transformer with a vacuum circuit breaker
When a vacuum breaker is used to disconnect an unloaded transformer, high overvoltages may result on the secondary side. The phenomena of current chopping and multiple reignitions after contact opening, shortly before current zero, play a significant role in generating these overvoltages, Furthermore, the transient recovery voltage (TRV) is also influenced by virtual current chopping which may lead to fast interruptions and reignitions. The paper reports on a vacuum breaker model implemented in the ATP-EMTP program. Simulations have been performed to determine overvoltages generated by the vacuum breaker, before and after suppression. Network elements were simulated by simplified models of limited complexity.
Kinemamtic analysis of flying-saw vehicle
The paper analyzes the kinematic motion of the flying-saw vehicle.After the analysis,it is concluded that the ac- celerating periods and decelerating periods in both forward and backward directions will follow sin~2αcurve and,in order to increase the sawing dimensional accuracy,flying-saw vehicle must come back as soon as possible while acceleration remains constant.Based on this premise,the paper gives out the equations of kinematic motion of the flying-saw vehicle in every sta- ges and one example result in a common situation.By now this method has been used in the real situation.