We have several obsolete German dc motors on Lenze vfds we are going to upgrade. Some of these motors have encoders on them and they are all on a Siemens Simatic S5 PLC.
We are going to go with ac motors and newer vfd's. Management is wanting to keep the Simatic S5 PLC. If we keep this plc do I need to have any programming changes done to the plc to recognize/communicate with the new vfd's? Will the Simatic S5 PLC be compatible with newer vfds? Finally would it just be wiser to upgrade the plc? We are not upgrading the whole production line just the palletizing section of this production line. This production line makes paper bags.

John,
Management always wants to keep the old. But the reality is that he S5 has been out of production for almost 2 decades now. I do not know how much development you are doing but we used to have special PC's capable to run windows 98 to be able to keep the development environment. If you need to replace hardware you will pay an arm and a leg for Spare unless you raid EBAY for parts abandoned by others like we did.
As far as your question it is difficult to give a good answer without really understanding how the interface between the S5 and the VFDs are done. If they use any kind of communication like Profibus, Modbus or other, the likelihood to be compatible is near 0. Your only chance is if you have a high end VFD that you could program to make it understand the S5. One of the option would be to ask Lenze for a drive compatible with their old standard. But then you are at their mercy. Overall this might be on the surface cheaper. But now you will be stuck with the old S5 and its costs. If the machine life expectancy is still long, then you will need to upgrade the S5. Now you are paying for the development twice.
If the interface is hardware then it is more likely to be doable. But then again a good study, case by case would be required.

Hi. John.
I agreed with Jean-Marc comment. For further development, its good idea to replace old S5 Simatic to newest S7.
Upgrade DC Lenze VFD to AC VFD's, you can contact Lenze USA (Ph. +1 (508) 278 9100 or Toll free +1 800 217 9100, www.lenzeamericas.com) for further advice.

do you have any email address ? so i can send you newest Lenze AC asyncrhonous motor and Lenze AC VFD's technical catalog for your reference.

The question sounds like a race car driver that realizes he has several miles of tire rubber left on his car and wants to use that rubber up before he puts new tires on his race car. I will leave my remarks to that for additional thoughts. Ken

Hi there John. Lenze AC VFDs were the most modestly proceed drive with encoder feedback that I knew of three years back when I was in the VFD game. It is all about the step 7 from Siemens and profibus. Keeping the old system has its issues, especially if it holds out for another 5 years or so when spares will be scarce and no doubt it will be unplanned maintenance costing downtime when it does fail. The benefits of preventative maintenance seems lost to most production engineers in the UK - have we not learnt from the 70's when the car industry began to fail against automated foreign competition???? Good luck convincing your boss to "do the right thing".

Mr. Tandiyono my email address is johnjones@graphicpkg.com. Mark Gibbons. Thanks. I am convinced that besides upgrading our vfd's if we upgrade our S5 plc we will be in a better position and have better reliability.

Hi. John, i was tried sent technical catalog to your email address johnjones@graphicpkg.com (as mentioned), but can not get-thru. Any other email address ?

Mr Tandiyono, an alternate email address is johntracey@roadrunner.com

I would go with new PLC and VFD's using Modbus or Ethernet IP for communication. Pay now or pay double later. I think you need a systems integrator. Good luck.

I like to post a different comment, if the S5 PLC is working well live it alone, why fix something that does not need fixing. If PLC is controlling the DC drives through Analog and Digital I/Os, all you need is a programmable VFD so you can duplicate the functionality of the existing DC drives. If PLC is using communication such as Profibus, you should look for a VFD that has the same communication protocol and can be reconfigured to mimic the existing DC drives.

Wow, a really technical report, what a treat to read it….I have had enough
to avoid all the c r a p on the screen that is consistent for months.
AWFUL; Ken m.

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