Trend Toward Integrated Safety in AC Drives

Posted by Dave Gazda on Jul 29, 2015, 10:19:00 AM

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Trend_Toward_Integrated_SafetyOver the past years, manufacturing processes have increased in complexity and the move toward modularity of machines has caused the safety functions to move away from the classical centralized safety designs (for example, deactivation of the complete machine using a main switch) and into the machine control system and/or the integrated AC drives.

Less Interfering Safety Functions

Integrated safety functions act much faster than those of a conventional design. The safety of a machine is increased further with AC Drive Integrated Safety. Furthermore, safety measures controlled by integrated safety systems are perceived as less interfering by the operator of the machine due to the custom actions, so the motivation to consciously bypass safety functions is significantly reduced. In addition, a significant increase in productivity can be realized because the changeover times can be shortened and during this changeover, depending on the type of machine, some subcomponents can even continue to manufacture.

AC Drives and Safe Torque Off

One of the key aspects of safety currently impacting motion control suppliers is the incorporation of certain safety features into AC drives, with safe torque off (STO) being the most common feature offered and used.

The push for safety has been led by the European market, and AC drives must incorporate STO to effectively compete in many European countries. In the Americas, STO has also evolved as a standard feature in some AC drives, but STO is still seen as a way to differentiate products rather than as an absolute requirement, as it is in Western Europe.  In the Asian market (excluding Japan), STO is not a requirement and is typically only requested by machine builders who export machines to other regions. The difference in adoption of STO in Europe and the Americas compared to Asia is having the largest effect on Asian suppliers as they look to expand their business into other regions; an AC drive product with STO must be developed to effectively compete.

The AC drive market is also trending towards more advanced safety features, including but not limited to the following:

  • Safe Stop 1 (SS1)
  • Safe Stop 2 (SS2)
  • Safe Limited Speed (SLS)
  • Safe Speed Monitor (SSM)
  • Safe Direction (SDI)

Advanced safety features may be integrated into the drive, as STO is typically offered, or provided through optional safety hardware or software modules, depending on the drive manufacturer.

Cost of Safety Features

ac drive units shipped with safety functions

There are over 15 different safety features currently being incorporated into AC drives. Of course, some of the advanced safety features added to a drive or safety module may increase the cost of that AC drive. To balance demand for safety features with AC drive pricing strategies, suppliers of motion products face a difficult task in anticipating which features will have the highest future demand and deciding which (and how many) to pursue in upcoming product developments.  As illustrated in Figure 1, the number of AC drive unit shipments enabled with safety features is forecast to increase significantly from 2012 to 2017 as the drive manufacturers make these features more readily available.

 

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Topics: Machine Safety, Safety, Drives

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