PLC Output Module

[PA28]

Dear friends,

Our contractor is proposing to use the BMXDRA1605 (Schneider) DO module for controlling some pumps with an MCC. (Please see attachment).
From the data sheet i noted that all out puts are supposed to use a power sources with one pole connected together. I think this is not always possible.
I want to know if there are other models with outputs which are truly independent of each other.

Thank you.

 

[thebard3]

It think the BMX DRA 0805 or maybe the BMX DRA 0804T will provide the isolated outputs you want, depending on your voltage requirements.

 

[PA28]

Thank you. thebard3. Yes BMX DRA 0805 is with completely isolated outputs. Only 8 outputs per module, and therefore more cost per output. But it solves the problem.

 

[ScottyUK]

Use the card with the common rail to drive a bank of interface relays. When something goes wrong on one of the field circuits - when, not if - you only have a £5 relay to replace, not a £200 I/O card.

 

[GroovyGuy]

Howdt PA,
You have one of two options here;
1) Either use the isolated DO card as the bard3 suggested, or
2) Install interposing relays, on a non-isolated type of DO card, as Scotty suggested
This assumes of course that each motor starter is equipped with an individual Control Power Transformer (CPT). Note it is possible to use a non-isolated DO card with a series of motor-starters that are sharing a common CPT. This is not a common solution though.
All in all, I prefer Scotty's solution (together with a 16-pt, or 32-pt DO card).
GG

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[PA28]

Thank you for the suggestions by ScottyUK GroovyGuy. All the starters are with individual control transformers which can be kept floating, but connecting them through the PLC, i think is not good. Therefore providing a bank of interposing relays, should be in a separate compartment with separate control transformer. This will also add to to interdependence between starters which we try to avoid. Considering above, i think the totally isolated output as suggested by thebard3 is better. Thank you.

 

[thebard3]

No problem ever exhibits a single solution. There are always alternatives with trade-offs for each. Glad to be of help.