Shunt controller

[akbar41]

I am in a PSU in India . I want to control a 32v dc relay when shunt voltage reach a 60mv state. Actually I want to control dc excitation of a GE locomotive generator which has no differential protection. can anybody help in this project.

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[mbarazeen]

you can use an op-amp comparator, there are number of op-amps you can chose, i have attached an example that may be helpful.

 

[Reloadron]

If this is for a commercial application I would use one of these units which do a very nice job with mV inputs off shunts and offer a low pass filter built in. I would program it for 0 to 100 mV = 4 to 20 mA output. Then run the 4 to 20 mA out through a 500 ohm precision 1% resistor so the 0 to 100 mV in now becomes a nice clean 2 to 10 volts out. I would run that 2 to 10 volts into a comparator like the LM311 some examples of which can be found here. This gives you a nice span to work with from your shunt and takes care of any noise. That is one way I would think about if this is going to be a commercial application.

Ron