Motor Contactor and PLC operation
Motor Contactor and PLC operation
(OP)
I have been told that there is a distance limitation between the PLC output and the Motor Contactor coil. I have a PLC output located apprx 1800 feet from the motor starter. Is there a special relay that is required to take into account the excessive voltage drop that is present when trying to pull in the contactor? Also their is a good amount of capacitance that may cause the contactor to stay energized when trying to shutdown the motor. I have tried to research this and have come up short in finding any pertinent information. Any advise from those that have faced this issue I am very much eager to hear past solutions. Thanks in advance.





RE: Motor Contactor and PLC operation
If the 120 V ac power source is at the PLC and the contactor is 1800 feet from these, you might be OK (although 1800 feet is a long run for 120 V ac control)
If the 120 V ac power is coming from the starter, running 1800 feet to the PLC output and back, then you have a problem. The capacitance in the control circuit may provide enough voltage to prevent the contactor from dropping out when the PLC contact opens.
Is this a 120 V ac control circuit?
RE: Motor Contactor and PLC operation
P.U. VA 230
Coil Voltage 120
P.U Amps 1.916667
AC Resistance of #14 AWG per 1000 ft 2.7
AC Resistance of #14 AWG per ft 0.0027
Total Distance 1800
Total AC Resistance 9.72 ohms
Voltage Dropped 18.63
Percentage of VD 0.84475
Operation Limits 85% to 110% of Rated Voltage
I am at the threshold of this Coil's operation.
This assumes that a #14 fits in the Controllers terminal. If I had to use a #16 even worse.
Coil data found out htis site.
http://www
Can someone explain to me the difference in this Freedom Starter Coil Chart the difference in operation limits and Hot and Cold P.U Volts?
RE: Motor Contactor and PLC operation
But you still need to be concerned about the shunt capacitance of this long control circuit.
The best solution all around at this distance would be to use a dc powered interposing relay.
RE: Motor Contactor and PLC operation
RE: Motor Contactor and PLC operation
This might help: thread248-128558, although the Square D link doesn't seem to work for me.
RE: Motor Contactor and PLC operation
Distant Control of AC Relays, Contactors, and Starters, Document Number M-379
Good luck,
dpc
RE: Motor Contactor and PLC operation
http://eca
RE: Motor Contactor and PLC operation
You might consider using a field bus communications with a drop to this IO block. Then from the IO block have the contactor triggered off of this IO block. Then do a local power drop to this box and the power losses are a mute point.
RE: Motor Contactor and PLC operation
Steve Wagner
RE: Motor Contactor and PLC operation