(1) From the button mechanism, we know that the emergency power switch, whether it is normally closed or normally open contact, will rebound again without pressing in place (press to the end), thus invalidating the action. When the normally open contact is used, the emergency stop does not play any role when the emergency power switch is not in place (because the normally open contact is not closed); when using the normally closed contact, it is different, regardless of the emergency stop. The button is not pressed in place, only the contact action, the emergency stop will work.
(2) From its control line Needless to say, the most basic function of the emergency power switch is emergency stop in case of emergency, to avoid mechanical accidents or personal accidents. However, due to the long-term operation of the machine, the line, especially the part of the emergency stop line, may cause a faulty open circuit. When designing an electrical control system, the emergency power switch preferably also uses a normally closed contact.
(3) When the emergency power switch of an area is pressed, one pair of contacts cuts off the operation of the power equipment that needs to be stopped in the area, and the other pair of contacts enters the PLC to cut off the starting circuit of the power equipment controlled by the PLC.