Drive technology allows safety functions to be built directly into the drive in an effortless manner. This gives big benefits to machine builders, designers, engineers and users who want to meet proper safety requirements with less hassle while saving time and money.
Implementing a machine safety system from start to finish can be seen as a daunting and complicated undertaking. Thanks to new safety technology in drives and standardization that unifies requirements and terminology used in the market, this process has been made easier. New electronic safety solutions integrated into the drive are perfectly capable of replacing the use of traditional safety systems that involve hard-wired logic add-ons like relays and contactors. The safe torque off (STO) safety function comes integrated in many ABB drives. Using an optional safety functions module, additional safety functions be integrated into the new all-compatible ACS880 industrial drives.
A few of the most important benefits that can be obtained with integrated safety in drives include reduced design time and effort and easy commissioning of one or several built-in pre-programmed safety functions. Other advantages are reduced number of devices, amount of cabling and cost savings, as well as no wearing parts when compared to traditional electromechanical safety devices.
One of the initial key tasks of a safety designer's job is to conduct a risk analysis aimed at defining where safety is needed on the machine and then deciding which safety levels and functions are required for making the machine safe. To make this work easier, ABB’s Functional safety design tool (FSDT-01) helps machine builders, OEMs and system integrators to calculate, verify and document the required, designed and achieved safety integrity level (SIL) or performance level (PL) using a very logical stepwise procedure, in accordance with machinery standards EN IEC 62061 and EN ISO 13849-1.
The Functional safety design tool cuts the designer’s workload by simplifying and speeding up the design process, while simultaneously ensuring the safety design calculations are met according to standards. Additionally, the design tool is compatible with numerous safety libraries making calculations and device selection much faster and easier.
Safe torque off (STO), which is the safety function that brings drives safely to a no-torque state (e.g. emergency stop) and/or prevents an accidental unexpected start-up, is the compulsory foundation of integrated drive-based functional safety. STO is therefore built into the drive as an electronic safety function to be used as an alternative to traditional electromechanical methods such as contactors.
Underlining ABB’s commitment to drive-based functional safety, many of its drives have STO built-in as a standard feature. The ACS880 drive series is the best-equipped, most-modern example of integrated safety in drives, with STO as a standard feature and the optional SIL 3 or PL e rated safety functions module providing additional safety functions.
The optional, encoderless and TÜV-certified safety functions module works seamlessly with ACS880 drives. It offers several safety functions in a compact plug-in module. The functions include: Safe stop 1 (SS1), Safe stop emergency (SSE), Safe brake control (SBC), Safely-limited speed (SLS) and Safe maximum speed (SMS). For safety functions like safe direction (SDI) which require encoder feedback from the motor ABB supplies the FSO-21 safety functions module together with the FSE-31 pulse encoder interface. These integrate smoothly to the drives’ control unit.
The safety functions module is easy to commission and configure using Drive composer Pro, the common PC tool for the ACS880 drive series. Using the safety module, the customer gets straightforward functionality right in the drive and does no need to figure out how he is going to hook up and wire the logic with relays, resets and contactors. Instead, the customer makes them work in harmony with the drive’s functionality by simply commissioning these functions that are built-in the module based on the safety design. This in turn helps to avoid the electromechanical logic design task.
The main benefit is the integrated safety functions that work seamlessly together alongside the drives control system. The extensive diagnostic features aid in troubleshooting to keep the system continuously safe, with safety-related system messages part of the standard drive operation, and accessible through the drives control panel. Additionally, the design of the safety functions module means less maintenance and chance of breakdown as there are no wearing parts. The safety module is provides capability for speed-related safety functions regarding certain suitable applications. This results in lower costs and higher reliability.
Direct benefits for the machine builder, designer or machine user include less cabling, which saves costs and makes the safety design work on a smaller footprint. Faster response time also provides improved protection in an emergency situation.
The safety functions module is easy to connect to a safety PLC, such as ABB’s AC500-S. This makes it possible to build a larger safety system where the safety PLC controls several drives, and the safety modules provide the local safety functionality and feedback to and from each drive. Connection between drive and PLC is done using PROFIsafe over profinet connectivity. ABB also offers a wide variety of additional safety devices such as switches, contactors and relays.