Current measure, or something ...

[sapoleon]

Hi again. After some vacations, I'm back to work...

So, here is my question.

I have 3 x tri-phase heaters, that runs for heating the water of 2 tanks, and are being manipulated in PWM from a PID in the PLC. Now, the client want us to check and give a signal, if some of the heaters and phase of the heaters is kaput.
I was thinking in current measurment, but i think it is overdessigned for just a work/don't work signal. so...

Does anyone knows of some device, that can give me a signal for current flowing or no? Better if it is tri-phase.

Thanks again to everyone.

 

[ianingram]

I was thinking in current measurment, but i think it is overdessigned for just a work/don't work signal. so....

No, I don't think so...
It depends on your process..I have had experience in the food industry where the hot water is used to keep a 25 ton chocolate tank warm...If a heater fails, it is critical to get the backup heater online as soon as possible.

Does anyone knows of some device, that can give me a signal for current flowing or no? Better if it is tri-phase.

It depends on what is available in your local area.. Do a search for AC current switch... You might have to use 3 AC current switches in series to measure each phase current

 

[rdrast]

We are using these devices:
http://www.tempco.com/Instrumentation/current_indicators.htm

Along with the temperature controller output, we use them to indicate various faults...

   TC_OUT  |  CurrentIndicator  |  State

  On      |    True            |  Good

  On      |    False           |  Bad Heater element

  Off     |    True            |  Bad Heating SSR

  Off     |    False           |  Good

  

 

[Tom Jenkins]

Allen Bradley, Cutler Hammer, and Siemens all offer phase monitoring relays. They trip if the voltage or current on one phase is out of tolerance with respect to the others. They are usually used for motor protection, but should work for you as well.

 

[sapoleon]

Thanks for the replies. I have to talk with the client now for check the different possibilities. Was very usefull.