Just commissioning a machine which has a large motor with two pt100 sensors per phase but only one RTD input has been allowed for each phase in the PLC (AB Compact Logix). Has the designer messed up or is there a way I can connect these? Thanks.
PLC connection - 2 pt100 per phase
- Thread starter amberman
- Start date
Bit_Bucket_07
Member
You can't connect more than one RTD per input, if that's what you're asking. Sounds like the designer was not aware of the dual RTDs.
Tom Jenkins
Lifetime Supporting Member
Two RTDs per phase is a common spec. It is also common to only monitor one of the two. The second one is a backup in case of a wiring failure - you can't replace an RTD wound into the stator like you can one installed in a process pipe! Since the intent is usually to detect heat build up from excessive motor starts or an over current both RTDs would generally provide essentially the same temperature reading anyway.
nwboson
Member
Yup, I'm with Tom (or else my designs are wrong)! Them's just spares. Ignore 'em - or use them when any of the primaries croak.
Bering C Sparky
Lifetime Supporting Member
Tom hit the nail right on the head.
You see this alot in large generator windings also.
(you can't just go in and replace the RTD's if one goes bad so the manufacturer will install redundant in case one bites the dust)
You see this alot in large generator windings also.
(you can't just go in and replace the RTD's if one goes bad so the manufacturer will install redundant in case one bites the dust)
Hi,
Yes - agree with all the above. We have also seen this setup used where one set is used by our PLC for local monitoring and the other 'spare' set used by the client's MCC system to give dual protection. As stated above - very common in large motors.
Regards,
Rob
Yes - agree with all the above. We have also seen this setup used where one set is used by our PLC for local monitoring and the other 'spare' set used by the client's MCC system to give dual protection. As stated above - very common in large motors.
Regards,
Rob
Similar Topics
Hello,
I have an issue where I want to simulate an Siemens HMI panel, through NAT connection to a PLC. I have the possibility through extended...
I have got an Rockwell PLC 1769-L36ERMS . I have assigned a IP address to it . But every-time I Reboot the PLC it looses Communication to my PC...
Hello gentlemen,
Im working on a small project on TIA Portal, about establishing a Modbus TCP connection between my ET200SP plc and a socomec...
Hi all,
My ethernet port on my laptop recently broke and I was hoping to just use a usb-c dongle in the mean time to go live on my PLC until I...
Hello, I've been trying to learn this a while now and still have not found out how this works. I have an Omron CJ2M PLC and an ABB ACS 355 VFD...