A distinction is made between a safe STOP in three categories.
STOP of category 0 to EN 60204-1 (9.2.2):
Uncontrolled stop by immediate (< 200 ms) shut-down of the power supply to the actuators (refer also to 3.5.6).
STOP of category 1 t oEN 60204-1 (9.2.2):
Controlled stop by interrupting the power supply to the actuator level if, for example, the hazardous movement has been brought to a standstill (time-delayed shut-down of the power supply). Refer also 3.11.
Example (see figure): the controller enable of an electronic drive is shut down immediately by means of an enable of the STOP category 0 and the power contactor only after the operational braking time of the motor (= STOP category 1).
STOP of category 2 t oEN 60204-1 (9.2.2):
Controlled stop. The power supply to the drive element is not interrupted. Additional measures to EN 1037 (protection from unexpected restart) are necessary, e.g. by the use of safety-related standstill watchdog.