Applicable Systems
PowerFlex 753
Symptoms
The EtherNet/IP communication to the PowerFlex 755 is lost. The PLC reports a module fault and the drive's EtherNet/IP status LED turns red. The drive continues to run at its last commanded speed if enabled.
Possible Causes
- Ethernet cable disconnected or damaged at the drive RJ45 port
- IP address conflict or incorrect subnet configuration
- Network switch port in error state or disabled
- EMI from adjacent power cables corrupting Ethernet frames
Troubleshooting Steps
- Step 1: Check the RJ45 connector and cable continuity with a cable tester
Cable passes continuity and shield tests; link LED is solid green - Step 2: Ping the drive IP address from a laptop on the same subnet
Drive responds with <5 ms latency and 0% packet loss - Step 3: Verify the drive IP address, subnet mask, and gateway match the network plan
No duplicate IPs; all settings match the PLC configuration - Step 4: Reroute the Ethernet cable >300 mm from power cables and verify shield grounding
Communication restores and remains stable under load
How to Reset
Acknowledge the communication fault in the PLC after restoring the network link. The drive can continue running if configured for Run on Comm Loss but verify this is intentional.
Common Replacement Parts
- 20-750-ENETR: Allen-Bradley PowerFlex 755 EtherNet/IP module (Verify firmware revision matches the drive main control board)
Frequently Asked Questions
- Q: Does the drive stop if EtherNet/IP fails?
Only if Parameter 688 (Comm Loss Action) is set to Fault or Stop. The default is often Ramp to Stop or Continue Last.
- Q: What is the maximum Ethernet cable length?
100 m per segment with Cat5e or better shielded cable. Use industrial Ethernet switches for longer runs.
Source: Rockwell Automation PowerFlex 750-Series Installation Manual, Publication 750-IN001
Category: Electrical