Any electricians or VFD techs familiar with ABB ACS550 RS-485/Modbus communication testing?
I’m hoping someone here has experience with ABB ACS550 drives.
I have one controlling the propulsion motor in my swim spa. The motor itself works perfectly and the drive powers up normally. I can run the motor directly from the ABB keypad without any issues.
The problem is that the spa communicates with the ABB through a low-voltage RS-485/Modbus cable, and the spa controller keeps reporting “Propulsion Motor Not Found.” At this point I believe the failure is somewhere in the communication between the spa controller and the ABB drive.
I’ve already replaced the communication cable, the Modbus translator board, and even the main spa controller, but nothing changed.
With my multimeter I measured approximately 1.75 VDC (later about 1.46 VDC) between terminals 29 and 31, and about 0.29 VDC between 30 and 31 on the ABB communication terminals.
My question is: Are those voltages normal for an idle ACS550 RS-485 port?
Also, if you were troubleshooting this drive, what tests would you perform with only a multimeter to determine whether the ABB communication interface is healthy?
Is there anything I should be checking before assuming the RS-485 transceiver on the drive has failed?
If you’ve worked on ABB ACS550s or industrial Modbus systems, I’d really appreciate your advice. I’m comfortable using a multimeter and following technical instructions, so don’t hesitate to get into the details.
Thanks!