International standard EN/ISO 13850 (replaces standard EN 418) specifies
the functional requirements and design principles of emergency stop
devices.
Stop types:
Stop category 0 and/or stop category 1 and/or stop category 2 stop functions shall be provided as indicated by the risk assessment and the functional requirements of the machine: - Stop Category 0: Stopping by immediate removal of power to the machine actuators (i.e. an uncontrolled stop – stopping of machine motion by removing electrical power to the machine actuators)
- Stop Category 1: A controlled stop (stopping of machine motion with electrical power to the machine actuators maintained during the stopping process) with power available to the machine actuators to achieve the stop and then removal of power when the stop is achieved
- Stop Category 2: A controlled stop with power left available to the machine actuators