Self-hold loop of electric control system of roller type electric-traction coal mining machine

The utility model relates to the field of an electric control system of an electric-traction coal mining machine, and particularly provides a self-hold loop of the electric control system of a roller type electric-traction coal mining machine. The self-hold loop is connected with a PLC (Programmable Logic Controller) and also comprises a direct-current relay, wherein two coil lead pins of the direct-current relay are respectively connected with an input terminal common port and an output terminal of the PLC; an output terminal common port corresponding to the output terminal is in short circuit with a contact of a direct-current power supply on the PLC; and one pair of normally open contacts of the direct-current relay is connected with a start button of the coal mining machine. By utilizing the normally open contacts of the direct-current relay as self-hold contacts of the self-hold loop, the direct-current relay is unlikely to be damaged in comparison with a conventional soft relay which is arranged inside