about constant current source 1

[bulancak]

hello, i want to have information on constant current sources, a constant voltage source is practical and reasonable but where do we benefit this kind of a source? what needs constant source?? or there is another explanation ?

 

[waross]

Many of the first street light installations were wired in series and powered by constant current transformers.
Series lighting from a constant current source worked well for airport runway lighting also. There is a vast installed base of industrial instrumentation which uses an adjustable constant current source. To make this more interesting, the device that controls the current is often remote from the device that supplies the voltage.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[dpc]

http://en.wikipedia.org/wiki/Current_source

As an electrical engineer, you really should be able to do at least some preliminary research on such a basic question.

Please review basic on-line sources and come back with a more specific question.

 

[bulancak]

i dont agree with u, if you read the waross's explanations you see that this kind of knowledge cant be learned from books, they tell u theory theory theory, in fact i couldnt get where do we use these kind of sources if you know tell us...

 

[alehman]

I think there may be a language barrier here.

The way the question was worded, it sounds as if you do not understand what a constant current source is. If that is the case and you are an engineer as you stated by joining eng-tips, then it is appropriate that you educate yourself on the basics before posting. This is made clear in the posting policies rule #1.

FAQ731-376: Eng-Tips.com Forum Policies

If English is not your native language and you need help expressing your question, it would be beneficial if you could state this. e.g. "I do not know how to ask, but I am trying to understand how a constant current source is used in power systems."

 

[VTer]

CT's can be viewed as a ideal/constant current source. That is why u always want to short unused CT's. (CT's are used everywhere)

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[VTer]

if that is what u were wondering about

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[wolf39]

bulancak:

One practical application of a D.C. constant current source is the precise determination of ohmic resistances of large generators. Constant current sources can deliver currents with an accuracy of 0.1% or better. You feed a constant current of, lets say, 25 Amps to the collector rings (slip rings) of a field winding and then measure the voltage drop across the collector rings. By utilizing the Ohmic Law you get the most accurate ohmic resistance possible.

In earlier times the situation was less comfortable. You had to use a battery, a series resistance for current adjustment as well as a current meter and a volt meter.

Regards

Wolf

http://www.hydropower-consult.com

 

[bulancak]

alehman, i think you dont have a fine english or understanding of it. because when i look back at my post i see that there is an engineer who knows constant current sources but dont know about its application fields.I think dpc and you especially have some understanding problem.if so i advice you to have some tony buzan books as far as i know they are unguent for you...

 

[DanDel]

bulancak, alehman and dpc are trying to help you. No offense meant, but it's obvious who has the problem here with the English language.

 

[opmgr1]

Gentlemen please keep it civilized and professional. This is not the site to be posting insults!

 

[bulancak]

okey i think you have a funny ally between you look at the question:
"where do we benefit this kind of a source? what needs constant source?? "

i think it is very difficult for you to understand the aim of asking this question. ? am not asking you the theory of this but practical use in industry. ? think you three have a high esteem of yourself.? advice you to read the kind explanations of vter and wolf39. Because they were intelligent enough to understand such an easy demand of a man who tries to get information on USE of C.C.S.es...

 

[DanDel]

I'm assuming you're asking for examples of what practical applications would use a constant-current source. Possibly, the examples given aren't detailed enough?

From my experience, I have seen the airport runway lighting that waross has already mentioned.

For a further explanation (if needed), the series lighting units used in this application are rated in amps, so no matter how many are used (change of circuit impedance), the constant current source adjusts the voltage to keep the current constant. You can see how, for an application such as this, with many lamps spread over a long distance, there would be a significant savings on wiring compared to running the lamps in parallel with a typical (constant voltage) source.

 

[bulancak]

thank you for your help, it is a precious knowledge for me..

 

[MJR2]

Electromagnets will need constant current supplies to provide consistent magnetic fields.

Mike

 

[TurbineGen]

Ductor testing and other low resistance tests such as transformer winding resistance use a constant current source.

------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[WhyDoYouAsk]

Flourescents prefer constant current; the ballast converts the wall outlet voltage source into a current source.
Since voltage sources can deliver ~infinite current, they have downstream circuit breakers.
Compare the V-I curves for both.

 

[busbar]

I'm not certain, but would electroplating be a constant-current application?

 

[WhyDoYouAsk]

http://www.google.com/search?client...ectroplate+"current+source"&ie=UTF-8&oe=UTF-8

http://www.google.com/search?client...troplating+"voltage+source'&ie=UTF-8&oe=UTF-8

Looks like Google bets even money on that. . .