Alternating current servo main drive system applied to mechanical crank pressing machine

The invention relates to an alternating current servo main drive system applied to a mechanical crank pressing machine, comprising a rectifier unit, a brake unit, a charging current limiting unit, an energy storage capacitance box, an inversion unit, a current feedback unit, a control unit, a signal interface and a processing unit, wherein an external power supply unit of electric equipment supplies power to a servo motor via the rectifier unit, the brake unit, the energy storage capacitance box and the inversion unit, the charging current limiting unit is arranged between the rectifier unit and the brake unit, the current feedback unit is arranged on a connection circuit from the inversion unit to the servo motor, and the rectifier unit, the charging current limiting unit, the brake unitand the current feedback unit are respectively provided with a path of output to the signal interface and processing unit. In the invention, energy is from the energy storage capacitance box, and theservo motor can be directly driven without adding the power supply capacity of the external electric equipment, thereby directly driving a crank; and through detection of voltage of a direct current bus and application of a backoff algorithm, turbulence of fluctuation to control can be counteracted, thereby improving the control effect.