This　paper　proposed　a　sensorless　online　opening　time　estimation　method　of　contactors　based　on　the　coil　current.　In　the　proposed　method,　the　electromotive　force　containing　the　armature　displacement　information　was　converted　into　the　coil　current　by　controlling　the　coil　voltage,　and　the　opening　time　was　estimated　according　to　the　corresponding　relationship　between　the　coil　current　peak　and　the　armature　displacement　when　contacts　just　part.　The　relationship　was　deduced　theoretically　from　the　mechanical　armature　motion　and　the　variation　of　coil　inductance.　According　to　the　relationship,　a　compensation　resistor　was　configured　in　the　coil　activation　circuit　to　improve　estimating　precision.　Compared　with　the　opening　time　estimation　method　based　on　contact　voltage,　the　proposed　method　has　higher　estimating　precision,　which　can　keep　the　fracture　of　contacts　and　meet　the　requirements　of　miniaturization　at　the　same　time.　The　estimation　results　can　be　used　as　feedback　to　establish　an　application　example:　a　zero　point-on-wave　opening　whose　delay　can　adjust　automatically　according　to　the　change　of　opening　time.　The　feasibility　of　the　proposed　estimation　method　is　proved　by　an　experiment　in　different　contactors.　©　2022　Chin.　Soc.　for　Elec.　Eng.