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Bryll

Inverters on Profibus

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Hello, Tried to get some good and clear answers at the Siemens forum, decided to try here aswell. I have a setup with 12 G120C inverters and three gas burner units on a profibus line. If I unplug any of the devices will I of course get an error from the loaded OB. But, now and then can I lose the connection to two or more of the inverters without any notification. It seems that the communication is up and running, but the don't respond to any commands. The normally green LED on the inverters switch over to flashing red when they stop to respond. They will also show fault code 1910. I am using standard telegram 20, this is also set in the inverters parameter lists. Another funny thing is that the fault bit in the status word is always set. Even when the inverters don't hav any faults or alarms. ZSW looks like this (with or without response from the inverter): Bit 0 = 1 (Ready for switching on) Bit 1 = 1 (Ready for operation) Bit 2 = 0 (Running) Bit 3 = 1 (Fault) On all the time, even when there is no faults in the inverter Bit 4 = 0 (No coast down active) Bit 5 = 1 (No fast stop active) Bit 6 = 1 (Switching on inhibited active) Bit 7 = 0 (Alarm present) Bit 8 = 1 (Speed setpoint - actual value deviation within tolerance) Bit 9 = 0 (Control requested) Bit A = 0 (f or n comparison value reached) Bit B = 0 (I, M or P limit not reached) Bit C = 1 (Reserved) Bit D = 1 (No motor overtemperature alarm) Bit E = 0 (Direction of motor rotation) Bit F = 0 (Display CDS) Anything I might have missed or done wrong ? Edited by Bryll

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How does your cabling look? Away from motor leads etc? A red light on the cu means your losing comms Did you check shields and cable? Edited by jrw

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All the cables is good, motorcables are of the good expensive shielded type and profibus cable and connectors are also good. One thing that puzzles me is that I had to perform a byte swap on the CW before the inverters would accept it. The speed setting data don't need to be swapped. The feedback SW don't need to be swapped, it's good as it is. The fault bit is always active, even when the inverters don't show any faults or error. Communication speed is set to 93kbps, so I don't think it's a speed issue that they drops out. I have 12 inverters and three Krom Schröder burner control units on the PB communication. If I disconnect the burners will they reconnect as soon as I put back the PB plug. The inverters not. Is there any setting I can do in the parameters of the inverters so they will try to reconnect ?

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So does it ever work properly? Can you ever control the drives and get a solid green comms light? Also, why the odd baud rate ? 1.5meg is default By default the drive should reconnect comms but the fault needs to be reset Resistors turned at the ends? Edited by jrw

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Yes it works most of the times, but sometimes are two or more lost. The communication light are nice and green until they are disconnected. I tested to lower the baud rate, and couldn't see any difference. Didn't change back to 1,5mbps, don't need it that fast. The drives don't reconnect, I have to do it at each drive. Termination is on at each end, no other is on. Checked the line a couple of times now.

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