What is the difference between stop category 0 and category 1?
In IEC 60204-1, Category 0 is an uncontrolled stop produced by removing power immediately. Category 1 first decelerates in a controlled manner and removes power after the machine has stopped. Category 2 stops in a controlled manner but keeps power on. An emergency stop function can only be Category 0 or 1; Category 2 cannot be used as an emergency stop.
The difference lies in when power is removed.
- Category 0: drive power is removed instantly. The stop happens through the system's own friction and mechanical brake — that is, it is an uncontrolled stop. It is the simplest architecture, depending on the fewest components, and for that reason the most reliable.
- Category 1: the drive is first decelerated in a controlled manner (for example with the inverter's ramp), and power is removed after it has been confirmed that the machine has stopped. The stopping distance is shorter and mechanical stress is reduced, but the deceleration function itself also becomes part of the safety chain.
- Category 2: a controlled stop is performed but power is not removed. It is suitable for production stops, not for emergency stops.
On lifting machinery the choice is usually determined by the behaviour of the load. On a crane where the brake grips mechanically when power is removed, Category 0 is the correct and straightforward choice. On horizontal movements with large inertia, sudden removal of power can set the load swinging, so Category 1 may be preferred.
These definitions are general standards knowledge; which category your machine has to implement is determined by risk assessment, and the electrical requirements are determined within the scope of EN IEC 60204-32.
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