Research On Electrical Contact Performances Of High-voltage And High-power DC Relay

In recent years,high-power DC relay has been aiming to develope to be capable of switching higher voltage and larger current circuit,and to be miniaturized and longer electrical life,which puts forward higher requirements on the electrical performances of the contact system.Thus,it is of great significance to study the key factors that affect the electrical performances of the contact of high-voltage and high-power DC relay.A set of experimental system was built to test the electrical performances of the relay contacts,which could simulate different atmosphere environment,could be convenient to adjust the intensity of the transverse magnetic field and the separation speed of the contact,and the voltage and current signals could be collected and stored in real time.A software of calculating experimental data including arc duration,arc energy,quantity of arc charge and contact resistance was designed based on the waveforms of voltage and current with LabVIEW.Experiments were conducted with symmetrical matings and asymmetrical matings of CuCr and CuW series of contacts,and CuMo85 contacts under DC resistive 270V/100A in air and nitrogen.The results show that CuW and CuMo85 were of better welding resistance than CuCr,and monotonic change of the composition proportion of contact material had no monotonic effects on welding resistance,erosion and arc duration of the material.When asymmetrical matings,the above mentioned electrical performances showed“intermediate effect”mostly,and the electrical performances were closely related to electrical properties of anode material.Experiments were conducted with CuW70 and CuMo85 contacts under DC resistive 200-500V and 40-150A in different surrounding atmospheres,specifically air,N₂,CO₂,O₂,Ar,0.8CO₂+0.2Ar?mixture of 80%CO₂ and 20%Ar?,and 0.5CO₂+0.5Ar?mixture of 50%CO₂and 50%Ar?,at atmospheric pressure.The results show that break arc durations in Ar and O₂were always the longest,while those in CO₂ were always the shortest.The smallest erosion rates were found in N₂,followed by the mixture of CO₂ and Ar,and O₂ showed the highest erosion rates.The highest contact resistance values were found in O₂,while those in N₂ and CO₂ were lower and more stable.A data fitting analysis was carried out,in which the break arc durations in different atmospheres and the multiple physical parameters of the atmospheres were treated as dependent variables and independent variables,respectively.The analysis shows that the break arc durations were positively correlated with the relative molecular weight,viscosity and thermal conductivity of the atmosphere,and were negatively correlated with the electron affinity,ionization energy and specific heat capacity.Experiments were conducted with CuW70 contacts under DC resistive 200-500V and 40-150A in the conditions with magnetic flux density of 50mT,65mT and 80mT,and separation speeds of the contact 70mm/s,85mm/s and 100mm/s,respectively.The results show that the total break arc durations and the arc durations of gas phase decreased monotonously with the increase of magnetic flux density.The total break arc durations and the arc durations of metalic phase and gas phase decreased monotonously with the increase of separation speed of the contact.The contact erosion could be reduced by increasing the magnetic flux density or increasing the separation speed of the contact.The above researches will be able to provide some references for the research and development of high-voltage and high-power DC relay.