Advances in drive-based functional safety give safety designers clear benefits in cost and time savings

2014-05-19 - Significant advances in drive technology now allow for safety functions to be built directly into the drive that controls motor and machinery movements. Designers and machine builders can simplify their work while also providing higher overall safety and protection levels.

Machine safety strategies aimed at protecting people, property and ecosystems can benefit from recent innovations in drive technology. 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.

Integrated drive-based functional safety
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 of ABB’s drives. Using an optional safety functions module, additional safety functions can 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 the easy commissioning of one or several built-in pre-programmed safety functions. Other advantages are the reduced number of devices, amount of cabling and cost savings, as well as no wearing parts when compared to traditional electromechanical safety devices.

Safe torque off (STO) is the required foundation for drive-based functional safety
Once the risk assessment of a machine is performed and a safety function has been selected as a suitable risk reduction measure, safety design and implementation can begin. Safe torque off (STO), which is the safety function that brings drives safely to a no-torque state (e.g. emergency stop) and 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 all-compatible ACS880 drive series are the best-equipped, most-modern examples 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.

Five safety functions in one safety module
The optional TÜV-certified safety functions module (FS0-11) works seamlessly with the all-compatible ACS880 industrial drives. It offers five optional safety functions in a compact ‘safety-yellow’ colored module package. The functions are: Safe stop 1 (SS1), Safe stop emergency (SSE), Safe brake control (SBC), Safely-limited speed (SLS) and Safe maximum speed (SMS).

The safety functions module is easy to commission and configure using the Drive composer pro PC tool. Using the safety functional module the customer gets straightforward functionality right in the drive and does not need to figure out how to design the function logic with wiring, 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 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 as 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 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. A faster response time also provides improved protection in an emergency situation.

A system-wide safety approach including drives and PLCs
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 achieved using a safety fieldbus built on the PROFIsafe protocol. ABB also offers a wide variety of additional safety devices such as switches, contactors and relays.

To learn more about ABB’s drive-based functional safety solutions visit drive-based functional safety.

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