PU Disconnection

What does PU disconnection mean?

A communication error has occurred between the PU (Parameter Unit) and the inverter, or the communication interval has exceeded the permissible time during RS-485 communication. This also triggers if the number of communication errors exceeds the retry limit. Loss of communication means the inverter cannot receive commands or send status, interrupting operation.

• PU (Parameter Unit) not securely seated in its port on the inverter.
• Damaged or disconnected communication cable for RS-485 (e.g., Modbus RTU) network.
• Incorrect communication parameters (e.g., Pr. 117-124 for RS-485) set on either the inverter or the master device.
• Excessive electrical noise or EMI (Electromagnetic Interference) on the communication bus.
• Master device (PLC/HMI) experiencing a communication fault or timeout condition.

Click steps to track your progress.

1. 1

   Ensure the PU (Parameter Unit) is firmly plugged into the inverter's communication port.

2. 2

   Visually inspect the RS-485 communication cable (if used) for damage, proper shielding, and secure terminal connections (e.g., SDA, SDB).

3. 3

   Verify that communication parameters (e.g., Pr. 117, Pr. 118, Pr. 119) match between the inverter and the master communication device.

4. 4

   Measure voltage levels on the RS-485 bus (A and B lines) to confirm signal integrity and proper biasing if applicable.

5. 5

   Temporarily disconnect other devices from the RS-485 bus to isolate potential communication conflicts or noise sources.

6. 6

   Check the master device's (e.g., PLC) communication settings and status for any active errors or timeouts.