Glossary · Stopping functions and safe states
Stop category 0
Under IEC 60204-1, stop category 0 is stopping by immediate removal of power to the machine actuators, resulting in an uncontrolled stop. The machine comes to rest by friction, inertia or mechanical brakes.
- Machine safety
- Risk assessment
In one sentence
Stop category 0 cuts actuator power at once. The stop is uncontrolled, so the stopping time depends on inertia and brakes.
Example
An emergency stop on a small bench grinder is wired as stop category 0: the contactor drops out, the motor loses power and the wheel runs down.
How it applies
- Machine safety: Stop category 0 is one of the two categories permitted for an emergency stop. It is simple, but coasting can be long for high-inertia machines, and removing power may release loads or clamps.
- Integrated systems: At drive level the same behavior is achieved with Safe Torque Off. The choice between category 0, 1 and 2 comes from the risk assessment for each stop function.
- Technical documentation: State the stop category of each stop function and the expected run-down behavior, so users do not reach in while parts still move.
- Evidence: Stopping time measurements show how long the uncontrolled stop takes in practice.
Stop category 0 vs. stop category 1
Category 0 removes power immediately. Stop category 1 first brakes under power and then removes it, which usually stops faster and more predictably.