PLC s7 200 problem conrolling inverter [VFD]

[sayedengg]

HI everyone, I have come across problem with PLC s7- 200 ,which has got two modules em 221 and em 232. This plc system controls various conveyors and speed regulation of the products between differnet conveyors.

The main problem is that the PLC is not able to output the inverters (VFDs) that control the conveyors. The voltage across the terminals in the PLC module [ EM 232 CN] that controls[ control signal ] inverters is constant,i.e, 10 Volts DC and hence drives are running at high constant speed instead of varying speed. Also, I have checked the wiring connection and the inputs of the plc; they are fine.

It was fine for almost 2 years + and now when the operator started machine, the drives are running speedly. I would appreciate if someone can help in how to get around the problem.

If there is anymore details need , I would surely help.



DETAILS :

- Delta inverter [ VFD - m ]

- s7 - 200 [ cpu 224 xp cn ]

-plc module : em 221 cn

- em 232 cn [ This is the one that outputs control signal to vfd ]



- On EM 232 CN module , The power is 24 VDC, there are two VFDS that are connected to it as follows :

- VFD1 on M0, V0 [on VFD it is, AV1 and +10V terminals ]



- VFD2 on M1, V1 [on VFD it is, AV1 and +10V terminals ]


Live and let live

 

[xnuke]

What is the input sensor that is used to measure the conveyor speed, and what is the input signal it is sending to the PLC?

If the input signal is failed low, it is likely that the code in the PLC (probably a variant of PID control) will output a maximum value of +10 V.

If the input signal is normal, ask yourself "What in the system has changed recently?"

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[sayedengg]

Thanks Xnuke for replying. The input sensor that is used to control speed are a series of photoelectric sensors, that slows or fast up the conveyor, depending on the product which is on the conveyor. Also the speed of the conveyor can be adjusted through HMI.

Live and let live