Starting circuit combining inching and long-term operation

In reality, sometimes it is necessary to manually operate the motor, and the motor needs to be able to run for a long time. The circuit shown in the figure is designed to address this problem. When the start button ST is pressed, the motor M starts normally, the circuit uses its normally open auxiliary contact to self-lock, and the motor M runs for a long time. When STP is pressed, motor M stops. If button SB is pressed, motor M starts. Since the normally open contact of SB is pressed, its normally closed contact is also disconnected. Therefore, after releasing SB, KM loses power and motor M stops. Therefore, this This operating mode is called "jog".