Panagiwtis Posted October 9, 2014 Report Share Posted October 9, 2014 I have a serious problem with V200-18-E2B (connected to a V570) that controls the inverter (GRUNDFOS CUE) of a pump via an analog output (0-10V). We are talking about a cooling system and I am using PID in order to control this analog output. The process value is a temperature sensor and the control value is the MI that controls the analog output (after Linearization) that goes to the inverter. When the PID is not active I use a strore direct function that stores the number 300 (30%) in the MI. The problem is that sometimes while the system seems to function normally, the HMI correctly shows that the inverter is working at 100% and I can see in the visilogic that the current value of the output MI is 1000 (100%) and 4095 in the real output (out of linearization block). However, in reality the inverter is working on its minimum safety setting (from its manufacturer) of 25% and when I measure the analog output of PLC with a voltmeter, the reading is 0V!!! I can't figure out why this happens, this problem drives me crazy and its a disaster for the customer...... Please, I need some help to find a way out of this..... PS1: I am not 100% sure but I think (i am many kilometers away from the plant at the moment) that this happens only when the system has made a complete cycle, the user has made a shut down to the system and restart it after this first shut down. PS2: The inverter sits inside the electric control panel and it's near the plc. Could this create a problem like this, or I can exclude that because of the fact that the problem doesn't occur all the time? Quote Link to comment Share on other sites More sharing options...
Henny Posted October 10, 2014 Report Share Posted October 10, 2014 Hello Difficult to say if your problem is related to EMC but perhaps the attached files that I got from our local Unitronics supplier may be helpfull? Regards Henny Minimizing EMI - System Design Guidelines.pdf Quote Link to comment Share on other sites More sharing options...
Panagiwtis Posted October 10, 2014 Author Report Share Posted October 10, 2014 Thank you for the reply, I have a similar pdf named "System Wiring Guidlines" but it seems that the one you posted contains much more info which I am about to start reading it now. The thing is that I am facing the exact same problem (with the exact same expansion card) as described in the first post here --->http://www.unitronics.com/forum_old/topic.asp?TOPIC_ID=137 Any opinions and suggestions are more than welcome because I am trying to prove to my supervisor that I am innocent and its not a "bug" of the program, because in the tags monitoring I can see that the MI that is related with the output has a value and the same time the voltmeter reads 0V... Quote Link to comment Share on other sites More sharing options...
Henny Posted October 10, 2014 Report Share Posted October 10, 2014 Hello You probably also tried(some) the suggestions that where stated in the old forum topic where you refered to? Found this stated in the installation guide of a V350 perhaps you should check this out and see if it helps. The 0V signal of the analog input and output must be connected to the controller’s 0V Regards Henny Quote Link to comment Share on other sites More sharing options...
MVP 2023 Joe Tauser Posted October 11, 2014 MVP 2023 Report Share Posted October 11, 2014 If the inverter's programmed minimum is 25% then it will ignore the PLC's analog output if it goes below 2.5V. Otherwise you may need to add a loop isolator - you may be running into a grounding issue. Joe T. Quote Link to comment Share on other sites More sharing options...
Panagiwtis Posted October 13, 2014 Author Report Share Posted October 13, 2014 If the inverter's programmed minimum is 25% then it will ignore the PLC's analog output if it goes below 2.5V. Otherwise you may need to add a loop isolator - you may be running into a grounding issue. Joe T. That's exactly what's happening, the inverter works in the minimum 25% and in the HMI screen shows that it works 100% (as it should from the PID), and the tag related to the output has a value (4095), but the PLC sends 0V to the psysical output. Any suggestions? Quote Link to comment Share on other sites More sharing options...
Panagiwtis Posted October 13, 2014 Author Report Share Posted October 13, 2014 Hello You probably also tried(some) the suggestions that where stated in the old forum topic where you refered to? Found this stated in the installation guide of a V350 perhaps you should check this out and see if it helps. The 0V signal of the analog input and output must be connected to the controller’s 0V Regards Henny Thanks for the reply. At the moment I haven't the final electrical drawings on hand but I think that the 0V signal of the analog output is connected to the 0V, but I have to discuss it with the electrician that made the wiring. At the moment I am many kilometers away from the plant, so I can only assume things. The main thing is to make sure that IS NOT a bug of the program... Quote Link to comment Share on other sites More sharing options...
Henny Posted October 13, 2014 Report Share Posted October 13, 2014 Hello If the system works well and the drive is running above minimum speed you should see a value in the output MI between 0 and 4095 when in a normal situation the drive runs maximum when the output is 4095(perhaps you can show this to your customer?) and in the problem situation you describe the output MI is also 4095 but the drive is not running at max speed and the output value is 0 V then this is definitely not a program bug but a hardware(EMC) problem. The V200-18-E2B has two analog outputs so perhaps if the second analog output is spare then perhaps you could project the value of the analog output1(the one that goes to the drive) to the spare one(assign a MI to it and copy the value of the MI from the first output into this one) and see in a problem situation if this MI has 10 volt.Don’t know how if this not connected output would also be affected in a EMC situation but if it’s not then this would be a second proof that it’s not a software bug. Regards Henny Quote Link to comment Share on other sites More sharing options...
sgull Posted October 15, 2014 Report Share Posted October 15, 2014 I had a problem like this before. HMI was telling me that a drive output was at 100% and the drive was at minimum. When checking the linearization block for the output I had put in 4096 instead of 4095 for the max. What I think happened was that the output went to 4096 and off-scale and then defaulted to min. When I corrected this value and downloaded the problem did not come back. Might be worth checking. Regards Denis Quote Link to comment Share on other sites More sharing options...
Panagiwtis Posted October 15, 2014 Author Report Share Posted October 15, 2014 So, after all, what solutions i've got now, except changing the expansion card or moving the VFD away from the PLC? Any suggestions? 1 Quote Link to comment Share on other sites More sharing options...
Kikis Posted October 15, 2014 Report Share Posted October 15, 2014 Geia sou Panagioti, You need to make sure that the PLC 0V is connected to 0V of your VFD analog input. If yes, then you might need to isolate the loop via a signal conditioner like the one below: http://www.aliexpress.com/item/Electrical-Isolation-Signals-Isolation-DC-to-DC-Isolation-Transducers-Signal-Conditioner/2028180427.html I had a similar problem in the recent past and i also asked for help in the forum. http://forum.unitronics.com/index.php?/topic/2532-m90-analog-out-to-inverter-drive/?hl=lenze#entry8735 The problem was not solved until i replaced the VFD with a new one from another manufacturer! Quote Link to comment Share on other sites More sharing options...
bm_engineering Posted November 22, 2014 Report Share Posted November 22, 2014 If you still have not solved this, disconnect all wiring from the analog output and check the output from the PLC. If you are getting the expected voltage, then you have a wiring problem externally, possibly a short to ground. If you do not get voltage out then the problem is something internal, such as wrong configuration, or you have a bad analog output. I would second the earlier suggestion to move to a different output address and see what happens. Quote Link to comment Share on other sites More sharing options...
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