Glossary · Stopping functions and safe states
Stop category 1
Under IEC 60204-1, stop category 1 is a controlled stop with power available to the machine actuators to achieve the stop, followed by removal of power when the stop is achieved.
- Machine safety
- Risk assessment
In one sentence
Stop category 1 brakes the machine under power and then removes power, the usual choice for high-inertia emergency stops.
Example
On a robot cell, the emergency stop is a stop category 1: the robot brakes along its path, then the drives switch to Safe Torque Off and the brakes engage.
How it applies
- Machine safety: Stop category 1 is permitted for an emergency stop. The removal of power at the end must happen even if the controlled stop fails, so the time or speed monitoring is part of the safety function.
- Integrated systems: In drives, Safe Stop 1 implements this behavior. Coordinated axes may need to brake together to avoid collisions or dropped parts.
- Technical documentation: Describe the stop as users experience it and give the expected stopping time.
- Evidence: Test the stop under worst-case load and confirm that power is removed after the stop.
Stop category 1 vs. stop category 2
Both are controlled stops. Category 1 removes power afterward; stop category 2 leaves power available, so the actuators remain energized.