Control system of AC motor

The utility model discloses a control system of an AC motor, comprising a power supply transformation module, an overheating over-current protection switch, a zero-crossing signal detection module, a relay control module, a silicon controlled rectifier control module and a main control module. The main control module starts the relay control module at the position of a power supply zero point, as there is no high voltage at two ends of a relay in the relay control module at the moment, an ignition phenomenon does not occur on the relay, in addition, when the power supply zero point is detected, the main control module performs delayed processing and starts the silicon controlled rectifier control module to activate the motor; if the motor needs to be stopped, the main control module firstly stops the silicon controlled rectifier control module to cut off a live wire loop of the motor, and then stops the relay control module, at this moment, heavy current at the two ends of the relay has been cut off, so the ignition phenomenon does not occur at the instant of cutting off, and false triggering cannot be generated as the relay control module and the silicon controlled rectifier control module simultaneously control activation of the motor.