Siemens 314 CPU

[Pieter.Croucamp]

Good day
I recently Changed a screen on a Machine from OP7 to KP400 Comfort using TIA portal v12.

since the change the communication is a bit of a issue, it is running on a palletizing machine and if 3 specific motors (and only those 3) run The communications cuts out totally. All the motors run on VSD's and at different speeds.

This looked to me like a "noise" problem

I have tried the following:
1. Cleared the PLC and screen and reloaded both
2. Replaced the MPI cable with a better screened wire (6 core twisted pair with 3 screens) connecting only one side of the screens.
3. Removed the comms wire from the electrical cabinet and ran it outside and away from any possible source of noise.
4. Installed a ferrite on one side and the on both sides.
5. Deactivated the other port on the HMI.

but I get no change to the problem.

If someone had a similar problem before and could point me in the right direction I would much appreciate it.

Thanx

 

[JesperMP]

Replaced the MPI cable with a better screened wire (6 core twisted pair with 3 screens) connecting only one side of the screens.

Use Profibus cable and connectors. And connect the screen to a ground bar by a fat clamp over the braid, not just in the connector.

Do you have a good quality ground ?

On the motor side, are the motor cables screened ?

 

[Pieter.Croucamp]

HI Jesper
The CPu does not support profibus (to old and small).
The ground is good yes
I will look at connecting the screen to the ground bar and replacing the motor cables.

I like the Idea of getting rid of the problem instead of "hiding" the comms cable

thanx a mil

 

[ajay34]

hai....

i had come cross this problem ..maybe it work for you i not sure ..but i does for me ..

1) use screen profibus cable..which not share with motor power cable .
2) seperated ground for control panel (mimic board / where plc and relay located)
3) seperated high motor KW and Inveter (vfd ground)
VFD crate high harmonic if using for bigger KW motor

 

[KalleOlsen]

HI Jesper
The CPu does not support profibus (to old and small)...

The Profi plugs can be used on the MPI interface.
Both MPI and Profibus are RS485 and the same signal pins are used.

Kalle

 

[Pieter.Croucamp]

Hi Kalle

I am no expert on comms. I noted that the MPI plug uses 3 wires and MPI only 2 I am not sure what they are used for but will go investigate that option.

thanx

 

[Pieter.Croucamp]

Thanx for all the help.
I replaced all the motor wires with screen wires and earthed the screen from the HMI (only one side). I also removed a bridge between the 0v and earth that was placed by someone else.
I also rerouted the HMI wire to be separate from all other wires.
My problem is now resolved.

regards