The Siemens 6ES7331-7KF02-0AB0 module is a widely used tool in the Siemens automation field, known for its efficiency in collecting analog signals. However, many engineers face a persistent issue during its use: common-mode voltage. This problem has become almost a “feature” of the module due to its frequent occurrence.
Why Does Common-Mode Voltage Occur?
Despite the 6ES7331-7KF02-0AB0 module often experiencing common-mode voltage problems, the true cause often lies in the environment itself. Most industrial settings are less than ideal systems…
Improper On-Site Wiring
Electrical lines, such as power lines, are often not properly separated from signal lines, leading to interference and the generation of common-mode voltage. This issue is more pronounced with longer wiring, amplifying the effects of external interference.
Ground Potential Differences
When different equipment is grounded inconsistently, ground potential differences can occur, causing abnormal voltage between the signal line and ground, resulting in common-mode voltage.
Interference from Electrical Equipment
Devices like frequency converters and motors can generate electromagnetic interference. If these devices lack proper shielding or grounding protection, the signal circuit is vulnerable, leading to common-mode voltage.
These issues are typically the result of poor wiring, inadequate grounding, and other non-compliant electrical practices.
What to Do if Common-Mode Voltage Occurs?
The direct solution is to connect the common ground, as per Siemens’ recommendations:
According to Siemens’ guidelines, connect the circuit with common-mode voltage to an unaffected circuit. Specifically, terminals 11 and 20 can be short-circuited with the M-terminal of the circuit requiring grounding. This ensures consistent potential across all circuits, effectively resolving the common-mode voltage issue.
However, the best approach is to prevent the issue in the first place by addressing the root causes:
Check the Grounding System
If common-mode voltage arises, check the grounding system first. Ensure all equipment is properly grounded with consistent potential, and repair any grounding issues immediately.
Rewire to Avoid Cross-Interference
If the wiring is improper, consider rewiring to ensure signal lines are kept separate from power lines. For long-distance wiring, use shielded cables to reduce external interference and mitigate common-mode voltage effects.
Use Filters to Reduce External Interference
In environments with significant interference, filters can help eliminate external noise, protecting the signal. For long-distance wiring, filters can significantly reduce the impact of common-mode voltage on the system.
Try them
hope these tips help you resolve the common-mode voltage problem with the 6ES7331-7KF02-0AB0 module. Try them out and ensure smoother, more efficient operations!
