In view of the challenges associated with online monitoring of contactor electrical life

this paper proposes a sensorless contact erosion observation technique for contactors. First

the counterforce characteristics of the contactor are analyzed

and the theoretical method for observing current contact erosion according to the counterforce integral inflection point during the closing process is proposed

and the inflection point identification algorithm is designed

which lays a theoretical foundation for the erosion observation. Then

based on the flux closed-loop control

the movable core displacement observer and the electromagnetic force observer are designed. The contact erosion observer is further designed based on the identification of the counterforce inflection point. Finally

the theoretical and practical effectiveness of the proposed contact erosion observation method is verified by simulation and simulated experiment. The observation method proposed in this paper can used for the online observation of contact erosion of electromagnetically operated switches

including contactors

relays

and permanent magnet circuit breakers. Therefore

it is of great significance for reliable operation and predictive maintenance of switchgears.