Current monitoring control 2

[honeykuwait]

Hi everyone,
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.

 

[itsmoked]

Perhaps these.

http://www.omega.com/pptst/DP1610.html

http://www.omega.com/pptst/DP450.

Also if you search Omega's site for "alarm units" you will see others and even dialers that will call or page someone during an alarm. A dead chiller in Kuwait could definitely warrant a phone call.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[honeykuwait]

Hello itsmoked.
I checked the link you advised, but couldnot find any product which I can use with my CT 800/5A 15VA, for monitoring the current and setting an alarm 400-800amps.
Any how the link is usefull for me foe other requirements. Thanks.
Any one can help my original request?

 

[waross]

Browse the Omega site.
The alarm unit suggested by itsmoked may be used at least two ways.
1> Interpose a current transmitter between the CT and the alarm. I am sure you will find transmitters on the Omega site that will accept 0-5 Amps AC from the CT and output 4-20 ma DC to the alarm. Most accurate.
2> conect a suitable resistor across the CT output. Rectify the voltage across the CT/resistor and feed it to a suitable input on the alarm. Possibly a 0-10 millivolt input, or with a second resistor in series, a 0-20 ma input.
You may need a capacitor to take out the ripple. For monitoring motor current, an acceptable value of capacitor is not critical and may span three orders of magnitude. (The time constant may range from a few cycles to a few minutes. Depends on you individual requirements.)
Do you want to use a small capacitor and trip in three seconds at 120% overload, or use a large capacitor and trip in five minutes at 105% overload?
I'll pass it back to itsmoked to suggest actual component values.
respectfully

 

[Skogsgurra]

There are a few ready built ones.

http://www.abb.com/Product/seitp328...7d0059d266.aspx?productLanguage=us&country=US

is a complicated and probably very expensive one while

http://www.process-controls.com/HCS/current_relay_cr4395.htm

seems to be more suited to your needs. Just put the secondary current from your CT through the loop.

One of the simplest ways of sensing current is to use a reed element and put it so close to the conductor that it picks up at the desired current level. Needs some experimenting. You will need a holding circuit so it doesn't chatter and probably some sort of reset (manual or automatic, depending on the application).

I would rather buy than build. Try the second link.

Gunnar Englund

http://www.gke.org

 

[Marke]

Hello honeykuwait
What you are looking for is a current sensing relay.
These are quite commonly available from a number of suppliers.
I would suggest that you talk to your normal electrical component supplier/wholesaler and ask them if they have a current sensing relay available. That way, you should be able to get spares/replacements later if needed.

Alternatively, do a google search on "current sensing relay" and you will find a number of options.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[dpc]

You can use these. A shunt resistor is required across the input for a 0 to 5 amp input.

http://www.actionio.com/products/actionpak/alarms/ap1680_ap1690.html

 

[Skogsgurra]

And - above all: DO NOT POST SAME QUESTION IN SEVERAL FORA!

Just made a fool out of myself in answering same question twice - although with different wording.

Gunnar Englund

http://www.gke.org

 

[waross]

I liked both answers, Gunnar.
bill

 

[Skogsgurra]

You are too kind, Bill ;-)

Gunnar Englund

http://www.gke.org

 

[jraef]

honeykuwait,
There are several very good current monitoring relays on the market, most of which are specifically designed for use in CT secondaries. Also, many Solid State Overload relays have alarm functions built-in. This is one I happen to like.
ATC MPA-1000 . The problem is, I'm not sure you can find one in Kuwait (assuming that's where you are).

The trick for you is in finding a supplier that can support their product in your location. I know ABB, Siemens, Schneider and Toshiba all have offices there, and they all have very capable products.


Gunnar,
That means you must be capable of carrying out a meaningful argument with yourself!




JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[Skogsgurra]

It happens all the time. But I usually keep it between myselves.

Gunnar Englund

http://www.gke.org

 

[honeykuwait]

Thanks to all who submitted usefull informations. I thing CR4395 will be ok for my use. I shall get back.