Mitsubishi Electric · FR-D700 Inverter
This fault indicates a loss of communication between the inverter and the Parameter Unit (PU) or another device via RS-485. This can be due to a disconnected cable, incorrect communication settings (Pr. 75, Pr. 121, Pr. 122), or excessive consecutive communication errors. Loss of communication will stop inverter output, potentially halting the connected process.
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Verify the RJ45 communication cable is securely connected to both the inverter's PU port and the external Parameter Unit.
Check inverter parameters Pr. 117 (Communication Speed), Pr. 118 (Communication Station Number), and Pr. 119 (Communication Data Length) against the Parameter Unit's settings.
Measure continuity and inspect the RJ45 communication cable for physical damage (frays, pinched sections) and replace if defects are found.
Test the system with a known-good Parameter Unit or try connecting to a different communication port if available on the inverter.
Confirm correct termination resistor settings (e.g., dip switch on inverter or external device) on the RS-485 network if multiple devices are connected.