Wiring Motor ON/OFF status to PLC
Wiring Motor ON/OFF status to PLC
(OP)
Got a question for you guys.
Whenever we want a PLC ON/OFF status for the motor, we would run cables, provide a NO contacts to the PLC in series with the motor starter coil (see attached VACULOADER SCHEM 2.pdf). Now our engineer wanted to use EATON'S electronic overload relay (C441) and wanted to discard that NO contact. I looked at the C441 manual and it does not say how it sends a signal to the PLC whether the motor is ON or OFF.
On the MCC side, of course you'll know if the motor is running or not as the C441 display is mounted on the MCC panel, displaying the power and current measurements. But how does it send the ON/OFF status signal to our PLC and thus to the HMI?
Whenever we want a PLC ON/OFF status for the motor, we would run cables, provide a NO contacts to the PLC in series with the motor starter coil (see attached VACULOADER SCHEM 2.pdf). Now our engineer wanted to use EATON'S electronic overload relay (C441) and wanted to discard that NO contact. I looked at the C441 manual and it does not say how it sends a signal to the PLC whether the motor is ON or OFF.
On the MCC side, of course you'll know if the motor is running or not as the C441 display is mounted on the MCC panel, displaying the power and current measurements. But how does it send the ON/OFF status signal to our PLC and thus to the HMI?
RE: Wiring Motor ON/OFF status to PLC
Brad
It's all okay as long as it's okay.
RE: Wiring Motor ON/OFF status to PLC
Notice that they are in a dotted box? The dotted box means it's physically part of the also dotted box of the C441 up above. Hence that 95/96 contact is available at the physical C441 relay.
Now, notice that the dotted box stuff has a specific dot-dash pattern? That means it's all in the same physical unit. It appears to me that there is also a set of ON/OFF contacts in the C441. They series these two sets of contacts so the PLC knows the motor is running or not, regardless of the cause. Separate use of those contacts to the PLC would've shown the motor ON/OFF AND if there was a critical overload trip.
If you want further give us a link to the C441 manual.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Wiring Motor ON/OFF status to PLC
The NC 95/96 is the OL for the C441 relay. Whe we use it as a protection for the EOL itself or as the OL for the M coil. (I actually prefer using another OL for the M coil just in case one of the wire loosened up). But how does the c441 relay communicates the motor ON/OFF status to the PLC? through the comm. port (C441 module)? So whenever we used this EOL's then no need to do a hard wire from the MCC to the PLC, no more providing NO to the PLC?
RE: Wiring Motor ON/OFF status to PLC
The C441 EOL and its communication module are in the attachment that I uploaded (files combined in one PDF file). It also includes the vaculoader vendor drawing showing that they need ON/OFF status from the PLC.
RE: Wiring Motor ON/OFF status to PLC
Just to comment on this:
They series these two sets of contacts so the PLC knows the motor is running or not, regardless of the cause. Separate use of those contacts to the PLC would've shown the motor ON/OFF AND if there was a critical overload trip.
That's what we usually do. Now, our engineer wanted to take that NO contacts hard wired to the PLC and just jumper 2A and 2B. So my question is, how does the C441 provides the signal ON/OFF to the PLC without that NO contacts hired wired to it?
RE: Wiring Motor ON/OFF status to PLC
Note this is all over in the manual:
From the schematic the C441 is not energized if the motor isn't being called for. Hence the 95/96 contacts are open if there is a fault OR if the motor is not being called for so there is no need for another set of contacts that also 'show the motor is ON' as the two contacts would be redundant.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Wiring Motor ON/OFF status to PLC
Yep, it'll trip the EOL in the event of a fault but you're gonna see that when you're in front of the panel display (of the EOL), in front of the MCC. To an operator looking at the HMI in the control room how is he gonna see that? The HMI receives its signal from the PLC so, how does the EOL sends the motor ON/OFF status to the PLC without the hard wire NO?
RE: Wiring Motor ON/OFF status to PLC
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
RE: Wiring Motor ON/OFF status to PLC
If yes, this fancy protection relay and its expensive communication module are connected to the PLC right?
If it is, would not the PLC talking MODBUS not just query the C441 via the C441R about the motor run status? In which case why would extra wires and contacts be needed?
What else am I missing?
Edit Cross post with Jeff.. and I love his logic.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Wiring Motor ON/OFF status to PLC
Brad
It's all okay as long as it's okay.
RE: Wiring Motor ON/OFF status to PLC
Got that. That's probably the reason why we hardwired contacts in another project. But in this, we used AB E300 EOL w/o comm. ports. This one has a local disconnect switch (see attachment).
RE: Wiring Motor ON/OFF status to PLC
RE: Wiring Motor ON/OFF status to PLC
Brad
It's all okay as long as it's okay.
RE: Wiring Motor ON/OFF status to PLC
The one that I just showed was for a previous project (the one that did not use E300 communication ports, I don't know why). We wired NO contacts to the E300, one for IN2 and one for IN3, so the PLC knows if the loading spout is moving UP or moving DOWN. In the new project that I'm working on, the lights are wired to the MCC TB. Those lights are there just to show that the motor is running or not when you're in front of the MCC (see attached).
RE: Wiring Motor ON/OFF status to PLC
Brad
It's all okay as long as it's okay.
RE: Wiring Motor ON/OFF status to PLC
I'm pretty sure that the specs requires that all motors must be start/stop via the PLC. Totally agree with you on 95/96 contact as the EOL can communicate the OL status via the com port.