unexpected on/off of acs800 controlled by ac500 pm573 via profibus
A pair of acs800 vfds were installed in a plant ,where the both drives are controlled via profibus by ac500 -pm573 with cm572dp in addition to 6 acs800 vfds which was already connected to the pm573 controller . under observation while operation of the newly installed drives ,there exists a problem of unexpected stop of the drive followed by automatic start which is not permissible for the apllication . THe control word used for the drives are
If you are suspicious about communication failure, you can set Parameter 30.18 to Last Speed or No and test your system again.
If drive recognies a communication fault, it starts to run at same speed instead of trip or stop.
Despite all these, your drive still starts and stops continously, you have to check your PLC program(Control Word, Referance etc.)
Hope it helps.
the parameter 30.18 comm.flt func is already set to fault. if there been a fault occuring in communication the drive would have tripped and stopped. but in my case it starts again within seconds autonomously ,i think this is not the problem. is there any other troubleshooting parameters?
this is a good question! As you have observed, the value 1151 is right for the run command. If you are sure that during normal operation in cycle, the value 1151 not change, I think it is necessary to build a "trap" in sw plc to to find out what changes in the state of drive - CW.
A question: the 1151 value is transferred directly to the CW or the value 1151 is transferred with "sum" of the corresponding values/states?
In this 2nd case, you should check if it is to change one of the values which, in its sum the value 1151.
Hope this help you
this is the 2nd case!
Look the attached image: you have for each input command function block, a variable bool, particulary for start - stop - coast etc. ... are you sure that during operation of your cycle in the plc, any of these bits do not go to zero / one?
If this happens, the drive stops and then starts again....just like you said!
Check these variable in your plc cycle, I think that one of these change during cycle and stop-start your drive continuously.
Let us know about the results
Under serious observation of the drives during machine cycle i ve found out changes in main SW of the drives as follows (during above said problem) =1631 then 1231 then 1737 .There is no change in the main CW . It remains same as 1151 . PLease help me in troubleshooting this. Is there problem with PLC or VFD?