Using an inverter drives with integrated safety reduces the need for external safety components, simplifying configuration and reducing installation space. ABB UK offers this safety functionality is a built-in feature in the ACS880, with safe torque-off (STO) as standard.

With ACS880, additional safety functions can be commissioned with the optional certified safety functions module FSO-11 that includes safe stop 1 (SS1); safe stop emergency (SSE); safely-limited speed (SLS); safe brake control (SBC); safe maximum speed (SMS) as detailed below. The drives’ functional safety is designed according to EN IEC 61800-5-2 and complies with the requirements of the European Union Machinery Directive 2006/42/EC.

Safe torque-off as standard

Safe torque off (STO) is used to prevent unexpected start-up and stopping-related functions, enabling safe machine maintenance and operation. With safe torque-off activated, the drive will not provide a rotational field. This prevents the motor from generating torque on the shaft. This function corresponds to an uncontrolled stop in accordance with stop category 0 of EN 60204-1.

The safety functions module FSO-11

The optional safety functions module FSO-11 comes with a range of safety functions and a self diagnostic function that meets current safety requirements and standards, in one compact module.

The FSO-11 is seamlessly integrated with the drives, reducing the implementation of safety function connections and configuration. Installing FSO-11 results in less needs for cabling and provides a cost-effective solution packed into a single safety functions module to ensure safe drive operation.

Commissioning and configuration of the safety functions is done with the Drive composer pro PC tool. The drive and FSO-11 is easy to connect to a safety PLC using PROFIsafe fieldbus adapter module (FENA-11).

The operating frequency of the FSO-11 is up to 200 Hz of the drives output. The safety functions module supports the following safety functions (which achieve up to SIL 3 or PL esafety level (Cat. 3)):

1  Safe stop 1 (SS1) brings the machine to a stop using a monitored deceleration ramp. It is typically used in applications where the machinery motion needs to be brought to a stop in a controlled way before switching over to the no-torque state.

2  Safe stop emergency (SSE) can be configured to, upon request, either activate STO instantly (category 0 stop), or first initiate motor deceleration and then, once the motor has stopped, activate the STO (category 1 stop).

3  Safe brake control (SBC) provides a safe output for controlling the motor’s external (mechanical) brakes, together with STO.

4  Safely-limited speed (SLS) ensures that the specified speed limit of the motor is not exceeded. This allows machine interaction to be performed at slow speed without stopping the drive. FSO-11 comes with four individual SLS settings for speed monitoring.

5  Safe maximum speed (SMS) monitors that the speed of the motor does not exceed the configured speed limit.

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