AC Motor rotational control with PLC

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Kloë

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Flanders, Belgium
Hi,

I have a pretty simple electrical question for a conveyor belt (3phase 400V). I have an AC motor that can only be turned in SCADA. And only in one direction. The motor drives a transport belt that moves wood chips. Sometimes the belt is blocked because of a wood chip. This is 90 percent of the times solved by just turning the transport back a bit and then moving it back forward. A frequency drive is not necessary.

At the moment the only way to move it backwards is by switching the wires in the electrical cabinet and then turning the motor via teamviewer in scada. Which is not very practical. I want to install 2 switches at the conveyor belt:
  • Bistable switch that switches between auto and manual. If it is in manual you can not turn it with the scada for safety reasons.
  • Monostable switch with 3 positions: Forwards, 0, backwards

See my drawing below:
https://drive.google.com/file/d/1MzptVaKjufkX-bPA9mEd1HEtNg_25dBH/view?usp=sharing

I think this simple system is the easiest way to do this. However I am not sure if this is save. Is this system possible? Are their safety issues that I am overlooking? Is it possible to short circuit this system?

Thank you for reading this!
Hopefully I placed this thread in the correct folder. Sorry in advance if I didn't.
 
Kloë said:
Hi,

I have a pretty simple electrical question for a conveyor belt (3phase 400V). I have an AC motor that can only be turned in SCADA. And only in one direction. The motor drives a transport belt that moves wood chips. Sometimes the belt is blocked because of a wood chip. This is 90 percent of the times solved by just turning the transport back a bit and then moving it back forward. A frequency drive is not necessary.

At the moment the only way to move it backwards is by switching the wires in the electrical cabinet and then turning the motor via teamviewer in scada. Which is not very practical. I want to install 2 switches at the conveyor belt:
  • Bistable switch that switches between auto and manual. If it is in manual you can not turn it with the scada for safety reasons.
  • Monostable switch with 3 positions: Forwards, 0, backwards

See my drawing below:
https://drive.google.com/file/d/1MzptVaKjufkX-bPA9mEd1HEtNg_25dBH/view?usp=sharing

I think this simple system is the easiest way to do this. However I am not sure if this is save. Is this system possible? Are their safety issues that I am overlooking? Is it possible to short circuit this system?

Thank you for reading this!
Hopefully I placed this thread in the correct folder. Sorry in advance if I didn't.
Click to expand...
Don't see any particular problem but I would want to electrically and mechanically interlock the two contactors.
 
IMO the "relays" would need to be HP rated. Why not just replace the existing motor starter with a reversing starter. Probably simpler in the long run.
 
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