generate a warning for current drawn 1

[honeykuwait]

Dear all,
I have posted this in the motors and motor controls engg, but decided to post in this forum as well to search for a solution.

I have a chiller compressor motor monitored by a CT 800/5amp, 15va burden capacity.
I want to know is there any readyly available control unit which can be used to monitor the motor current using the mentioned CT and generate a warning for current drawn by the motor 400-800amp, (value settable). May suggest a suitable circuit to achieve the goal.- Regards.

 

[logbook]

A link to the current transformer would help.
Do you mean something like this one?

http://www.brunelcorp.com/ECC/CTX.HTM

It seems that you just put a low value resistor across the current transformer output and you will get a suitable AC signal to monitor. If you are going to make your own detector it will consist of a few resistors, a few capacitors and a comparator. You will also need some sort of power supply like a plug top 9V DC supply or similar. Is this an acceptable type of solution or do you just want to get an off the shelf module?

 

[honeykuwait]

Thank you logbook for the reply.
I really prefer to get an off the shelf solution, but as interested to do it by myself also provided I get a workable circuit. Your help for this is most welcome.
Regards.

 

[Skogsgurra]

Google "current sensing relay". That will produce lots of hits. One of them is this

http://www.crmagnetics.com/newprod/ProductView.asp?ProdName=CR4395

This device can take the wire from your CT and the loading is minimal.

Other relays with more orthodox looks are also available.

Gunnar Englund

http://www.gke.org

 

[logbook]

honeykuwait,

an off-the-shelf solution like the one suggested by skogs is going to be cheaper and easier if you only ever want to make one. You should search for one that does what you want. If no such beast exists then by all means go ahead and design one. In this case you will have to decide on or state the following:

1) What is the maximum primary current that is not a fault?
2) What is the minimum primary current that is a fault?
3) What is the nature of the alarm? (500W light bulb, serial data stream to a computer, 20mA LED current?)

If the answers to (1) and (2) are too close together (say within 20%) adjustment/calibration will be necessary.

 

[honeykuwait]

Hi Logbbok,skogsgurra (Electrical)
Thanks for the advise, I found CR4395 shall meet my requirement.I will come back after using the CR4935.