Ken Roach
Lifetime Supporting Member + Moderator
I am trying to troubleshoot a Profibus DP installation inside a large Siemens SIVACON motor control center and I hope somebody can help me out.
I am most familiar with using Profibus DP with conventional Profibus connectors, where you connect 1 or 2 violet Profibus cables to a big connector with a DB9 shell, and have a selector switch for termination. The more expensive ones can even run up to 12 MB/s.
This system uses terminal blocks and a trunk/drop configuration. There is a Profibus DP trunk made up of the violet cable going from terminal block to terminal block in the back of the MCC sections (up to 27 terminal block sets in the trunk) with 1 meter drop cables down to drives and Simocode Pro V motor starter/overloads in buckets.
The Simocode Pro V starters use the Profibus screw terminals, not a conventional connector with a DB9 shell.
The Profibus DP master is a DeltaV module, configured to run at 187.5 kb/s.
I realize this is on the low end of speed for Profibus DP, but every installation guide I have ever seen for Profibus DP says you should not build it with droplines. Yet this MCC was built this way by Siemens, and the Simocode Pro V overloads have screw terminals as an alternative to the DB9 shell connector, which implies that they are meant to connect to a non-connectorized Profibus DP network.
Is this the accepted way to wire up a Profibus DP network in an MCC at lower data rates ?
The DeltaV scanner is at one end and has a proper built-in terminator, but at the far end of the network instead of using a powered Profibus terminator they simply placed a 150 ohm resistor across A and B wires. Has anyone seen this kind of "informal" termination ?
The system evidently passed its factory acceptance tests but the customer is getting occasional "dropouts" of individual nodes and wants me to find the culprit.
Can anyone suggest some guidelines for 187.5 kb/s Profibus cable systems that do not use the conventional Profibus connectors ?
I am most familiar with using Profibus DP with conventional Profibus connectors, where you connect 1 or 2 violet Profibus cables to a big connector with a DB9 shell, and have a selector switch for termination. The more expensive ones can even run up to 12 MB/s.
This system uses terminal blocks and a trunk/drop configuration. There is a Profibus DP trunk made up of the violet cable going from terminal block to terminal block in the back of the MCC sections (up to 27 terminal block sets in the trunk) with 1 meter drop cables down to drives and Simocode Pro V motor starter/overloads in buckets.
The Simocode Pro V starters use the Profibus screw terminals, not a conventional connector with a DB9 shell.
The Profibus DP master is a DeltaV module, configured to run at 187.5 kb/s.
I realize this is on the low end of speed for Profibus DP, but every installation guide I have ever seen for Profibus DP says you should not build it with droplines. Yet this MCC was built this way by Siemens, and the Simocode Pro V overloads have screw terminals as an alternative to the DB9 shell connector, which implies that they are meant to connect to a non-connectorized Profibus DP network.
Is this the accepted way to wire up a Profibus DP network in an MCC at lower data rates ?
The DeltaV scanner is at one end and has a proper built-in terminator, but at the far end of the network instead of using a powered Profibus terminator they simply placed a 150 ohm resistor across A and B wires. Has anyone seen this kind of "informal" termination ?
The system evidently passed its factory acceptance tests but the customer is getting occasional "dropouts" of individual nodes and wants me to find the culprit.
Can anyone suggest some guidelines for 187.5 kb/s Profibus cable systems that do not use the conventional Profibus connectors ?