Method for monitoring motor power supply contactor on line

The invention discloses a method for monitoring a motor power supply contactor on line. The method comprises the following steps: acquiring a three-phase current of an output end of a motor contactor, and calculating an effective value based on the three-phase current; recording the starting time and the closing time of each phase of current, and determining threshold values of the starting time and the closing time of the three-phase current; comparing the recorded starting time and closing time with the starting time threshold value and the closing time threshold value; and judging the state of the motor power contactor based on the comparison result. On-line judgment of the working condition of the contactor is realized through on-line monitoring of the closing and starting processes of the motor, so that the purpose of fault early warning is realized; according to the invention, accurate acquisition of equipment operation data and accurate acquisition of the starting time of the motor are realized by usin