DIGITAL MANUFACTURING Safe Choices for Automation
EMC shielding joins functional safety, real time communications and stable operating environment as important factors to consider when choosing drive controllers for automation.
n the quest for higher levels of automation in digital manufacturing environments, more automatic machines are being placed in crowded cells with high levels of connectivity, both within the cell and to process control and monitoring equipment. As a result, the need
for reliable operation and reduced likelihood of failures due to radio frequency interference (RFI) has become more critical. In response, drive controller specialist, KEB Automation, is offering options on its products that provide the necessary protection, whatever the configuration might be. According to Mark Checkley of KEB, a number of factors need to be considered when choosing a drive controller for highly automated process plant and machines, including EMC protection. Amongst the other important factors to consider are
functional safety, real-time communications, ease of integration and feedback control.
FUNCTIONAL SAFETY Checkley believes that safety should be built into the drive controller functions rather than bolted on as an option. ”Buying drive controllers with integrated functional safety is likely to reduce the cost of installing separate protective devices as well as their associated cabling and installation costs,” he says.
Adding wiring and devices also introduces complexity when considering factors such as RFI, whereas built-in functionality is pre-tested at the overall assembly level rather than individually. The functions can be complex so a more simplistic approach reduces the burden on specification. For example, as well as providing basic STO (Safe Torque Off), it’s possible to provide scalable higher level encoder-based safety functions such as Safe Limited Speed, Safe Maximum Speed, Safe Speed Range, Safe Operating Stop, Safe Direction and Safe Emergency Limit.
REAL-TIME COMMUNICATIONS If machines or production processes are high speed, choosing drive controllers that provide real-time Ethernet-based communications interfaces, such as Ethernet IP, is critical in modern digital manufacturing processes and Industry 4.0 environments.
10 /// EMC Testing Vol 2 No. 1
❱ ❱ Crowded RFI environments in automated manufacturing cells place higher emphasis on shielding when selecting drive controllers
Similarly to the arguments surrounding functional safety,
it’s important that these real-time Ethernet-based interfaces are built-in and fully integrated with the drives and not simply provided as an add-on module, as these add-ons can create unwanted latency in networks.
STABLE OPERATING ENVIRONMENT In many industrial environments, ensuring the stability of drive controllers is sometimes overlooked. However, an EMC compliant assembly with efficient control cabinet and suppression systems is the basis for safe operation of machines and equipment. When choosing drives, it is therefore prudent to check what range of accessories the drives supplier can offer. Whilst these accessories can be sourced from a Third Party supplier, it is better to deal with a single supplier that can provide everything, optimised to suit their own specific drives and fully tested for compliance.
• Mains EMC filters reduce the cable-fed emission to the required limits of IEC 61800-3-C1/C2. Other variants may
DRIVE CONTROLLER PROTECTION A number of accessories are available that provide the means of achieving the right level of protection against EMC. By specifying the requirements, these can be supplied, installed and tested by the supplier, reducing the test burden at final configuration and commissioning of the automation cell.
• Mains chokes reduce the input peak current draw and the mains distortion.
• Output chokes and filters reduce the voltage and current stress of the motor winding.
• Combi-filters (EMC/ Output choke) are space-saving combinations consistently adapt and optimise the drive
• Sine-wave filters protect the motor winding from voltage peaks and allow the use of long motor cables.
• Harmonic filters reduce the low frequency mains distortion on rectifier supplied devices. These harmonic filters allow
• Sine-wave EMC filters allow operation of motors with long motor cables even without screening.
easy integration to a switchgear layout.
offer low leakage currents or the operation of special mains networks.
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