MM420 doesn't send data to PLC

Hi,

I have 5 MM420 inverters connected via RS485, PLC is communicating with them through USS communication. All was working well, until restarting electrical cabinet. After this 2 of the Micromasters lost communication with master (didn't generate NDR ready output from USS_Drive block).

It turned out that these inverters were receiving data from PLC, but didn't send data to the PLC.

As it was working before, I'm not sure where to look for issues. I was thinking about connection between inverter and the drive, as plc code and rs485 connection wasn't changed at all.

What do You think? Could some problem on the drive (we had few alarms with drive temperature sensors) mess up with USS communication?

 Hi,

Have you checked about the connection cables? Can you connect the BOP, reset the alarms/failures and try to communicate again?

Gostenn

Hi,

I have 5 MM420 inverters connected via RS485, PLC is communicating with them through USS communication. All was working well, until restarting electrical cabinet. After this 2 of the Micromasters lost communication with master (didn't generate NDR ready output from USS_Drive block).

It turned out that these inverters were receiving data from PLC, but didn't send data to the PLC.

As it was working before, I'm not sure where to look for issues. I was thinking about connection between inverter and the drive, as plc code and rs485 connection wasn't changed at all.

What do You think? Could some problem on the drive (we had few alarms with drive temperature sensors) mess up with USS communication?

Hey,

as it turned out,after power restart parameter P2013 has changed, thus communication was lost. As soon as I changed it, communication was back again :)

Strange thing is, this situation (change of parameter after power reset) happened second time already. Is it a common problem in Micromaster?