Experimental And Simulation Study On Break Arc Duration And Arc Motion During Breaking Process Of High-Power DC Relays

Nowdays,the study of electromagnetic relays is mainly focused on the applications of high voltage,high power,and high performance.In this condition,breaking reliability and electrical life become the urgent need for DC relays.In this paper,through theoretical calculation and experimental study,the characteristics of arc motion and break arc duration under different breaking speed and transverse magnetic field,in different atmosphere,are analyzed.It can provide a theoretical basis for the selection of arcing atmosphere,breaking speed,transverse magnetic field and the structure design of DC relays.Firstly,The dynamic time constant for CASSIE model is calculated based on the experimental arc voltage and current waveforms during breaking process,and the quantitative relationship between dynamic time constant and the atmospheric physical property parameters as well as voltage and current condition is obtained by data fitting.The minimum arc current is selected as the criterion of arc extinguishment,and the break arc duration under different voltage and current condition in different atmosphere is calculated based on CASSIE model.The result showed that the sequence of break arc duration in different atmosphere is H₂<SF₆<CO₂<N₂<Air<O₂<Ar,under most of the calculated voltage and current condition.Secondly,In order to calculate the arc motion characteristics during break process,some improvement work has been done according to the classic arc chain model,which divides the whole break arc ignition process into a two parts,one is short arc stage and another is bow arc stage.The variation of arc length and arc height is calculated by force analysis,based on the quantitative relation of dynamic arc time constant for CASSIE model and improved arc chained model.The results show that,with the increase of the supply power,the arc length and the arc height when quenching increase exponentially.Finally,In order to verify the calculation result of arc motion and break arc duration,the arc shooting experiments were carried out under different voltage and current conditions,different transverse magnetic fields and different breaking speed in Air.The experimental results show that the arc length when quenching is quite consistent with the calculated results,and with the increase of the transverse magnetic field and the breaking speed,the break arc duration decreases,however,which does not affect the arc length when quenching.With the increase of the circuit power,the measured value of arc length and arc height when quenching increases exponentially.And then,the phenomenon of arc restrike and arc root jumping are analyzed through the arc voltage waveform and the pictures taken by the high speed camera.The statistical results show that the average probability of restrike in the breaking process increases with the increase of the circuit power,as well as the mean times of restrike and the arc root jump for one breaking operation.