Controller and control method for alternating current contactor

A control method for an alternating current contactor, comprising:

• filtering and rectifying an external alternating current, and driving an electromagnet component by an filtered and rectified output;
• controlling on or off of a power transistor circuit by a microcontroller, the on or off of the power transistor circuit making the electromagnet component perform the actions of attraction, holding or releasing;
• sampling a voltage feedback signal, the microcontroller generating a control signal according to the voltage feedback signal and controlling the power transistor circuit with the control signal, so that the electromagnet component performs the actions of attraction, holding or releasing, wherein the control signal is a PWM control signal having different duty cycles during the attraction and holding of the electromagnet component, the PWM control signal having different duty cycles makes the current do not exceed a predetermined current threshold during the attraction and holding of the electromagnet component;
• sampling a current feedback signal, the microcontroller turning off the power transistor circuit upon detecting an overcurrent exceeding the current threshold;
• providing a switching circuit for adjusting the current threshold according to different stages, wherein during the attraction of the electromagnet component, the switching circuit is provided with a first current threshold, and during the holding of the electromagnet component, the switching circuit is provided with a second current threshold, the first current threshold is larger than the second current threshold;
• enabling a PLC control module, the PLC outputting a PLC control signal to the microcontroller when enabled, the microcontroller controlling the power transistor circuit according to the PLC control signal so as to control the electromagnet component to perform actions of attraction, holding or releasing.