Motor RTD

Does any one know where I can find a "simple relay type" device that I can connect to the RTD sensor in a motor that has an adjustable trip? I have been searching but it is to no avail. All I have come up with so far are extremely complex motor protection devices. Thanks.

basic loop controller

A basic limit controller can be found from Watlow at: http://www.watlow.com/products/controllers/co_basic.cfm

Partlow and West both make indicators that have relay outputs and/or alarm options. I like them because they are simple to use.
http://www.partlow.com/products/

You know I hadn't thought of using a limit controller. I had been concentrating on using some type of voltage/temp relay. AD has one for $149.00 that has dual alarm set points. Thanks for nudge in a different direction guys.
In appreciation! Free beer for all!

Minco has a packaged unit for motor winding RTDs that goes for around $1,000 - less expensive than a GE MultiLin, but not as many features either.

I generally just use an RTD input card on the PLC if there is one available for the platform I'm working on. Less money, I can program the logic any way I want, and if I choose to allow it the operator can adjust temp limits on the touchscreen the same way he adjusts the rest of the system, within the limits I program in. The first time I did it I was concerned about EMI/RFI on the RTDs from the windings, but this hasn't ever been a problem.

I agree with Tom

I use RTD input modules almost exclusively anymore because of the lower cost per point and the overall control that you get within your PLC programming and HMI.

Many RTD modules have built-in diagnostics also. Also, they are very reliable (have some RTD modules that have been running over 10 years now without a hitch), but I have replaced stand alone controllers!

Chris

Tom Jenkins said:

I generally just use an RTD input card on the PLC if there is one available for the platform I'm working on. Less money, I can program the logic any way I want, and if I choose to allow it the operator can adjust temp limits on the touchscreen the same way he adjusts the rest of the system, within the limits I program in. The first time I did it I was concerned about EMI/RFI on the RTDs from the windings, but this hasn't ever been a problem.

Click to expand...

Hi Tom!
Again 3-leter abbreviations, where only 'plc' is clear for me.
What is RTD in your speech? Is it as PT-100-type (almost linear) or as
-we speech PTC-resistor- where Resistance groving up very fast in designed temperature. PTC have typically used in motor windings with thermistor-relay.

I apologize, Seppo - these darned acronyms!

RTD = Resistance Temperature Detector, which is indeed generally the 100 Ohm Platinum type.

For us a PTC (Positive Temperature Coefficient) is also usually a thermistor, which we also use a lot for motor winding protection.

EMI = ElectroMagnetic Interference
RFI = Radio Frequency Interference

Thanks Tom !