I have a 24Vdc conveyor that I'm hoping to program it with an Siemens PLC.

My question is typically for a 3 phase motor you have to have a two contactors to allow the motor to go forward or reverse .Does the conveyor require two contactors in this scenario or can the PLC do the forward and reverse functions internally if the conveyor is wired into the DI/O?

 

The PLC can do the reversing logic but you still require a 3 phase reversing contactor, these have both mechanical and electrical interlocking, I also do interlocking in the PLC rung, Also in many cases, the motor O/L has two contacts, both NO & NC, I input the NO one into the PLC to advise the rung an O/L has occured and also help in trouble shooting.
Max.

 

I liked Max Headroom's reply because it is best practices. But also his user name brings back fond memories.
MmmMax ... Maxheadroom lol

 

The PLC can do the reversing logic but you still require a 3 phase reversing contactor, these have both mechanical and electrical interlocking, I also do interlocking in the PLC rung, Also in many cases, the motor O/L has two contacts, both NO & NC, I input the NO one into the PLC to advise the rung an O/L has occured and also help in trouble shooting.
Max.

Max while I absolutely agree as to reversing an AC motor, in this case the original poster is asking:

I have a 24Vdc conveyor that I'm hoping to program it with an Siemens PLC.

So we have a DC Motor which runs on 24 VDC. The PLC can manage the forward and reverse of the motor likely but much of this will depend on the specific motor and PLC. The PLC will likely control an H Bridge which based on command will reverse polarity to the motor for forward and reverse rotation. Things like motor current and PLC type need known. I know Siemens but Siemens markets dozens of PLC models.

Ron

 

So we have a DC Motor which runs on 24 VDC. The PLC can manage the forward and reverse of the motor likely but much of this will depend on the specific motor and PLC. The PLC will likely control an H Bridge which based on command will reverse polarity to the motor for forward and reverse rotation. Things like motor current and PLC type need known. I know Siemens but Siemens markets dozens of PLC models.

Ron

OK I missed the fact the motor was 24vdc but the same can still apply if the motor is directly picked up on line, a couple of DC rated contactors would be needed. there was no mention of a controller?
Max.

 

OK I missed the fact the motor was 24vdc but the same can still apply if the motor is directly picked up on line, a couple of DC rated contactors would be needed. there was no mention of a controller?
Max.

I agree, there was no real mention of PLC In / Out or PLC stimulus and no mention of motor current?

Been some years but when working with reversing AC 3 phase motors I was annimate about making sure my contactors were mechanically ganged and interlocked. Brought back some memories on that note.

Ron

 

If the OP was asking if the PLC output could be used to switch the DC motor direct, it would be a bad idea, I never switch unpredictable loads directly, regardless of the current rating of the output, a larger intermediate relay or switching device should be used.
Max.