AC current sensing
AC current sensing
(OP)
Hi
I am looking for a current sensing device with a response time of 100 ms or less that will be able to sense up to 600 amps this will be interfacing with an automation controller.Any input will be helpful
Thanks
I am looking for a current sensing device with a response time of 100 ms or less that will be able to sense up to 600 amps this will be interfacing with an automation controller.Any input will be helpful
Thanks





RE: AC current sensing
http://www.lem.com/
RE: AC current sensing
Use the LEM transducers with care on fast edges, or install it at the earthy end of the circuit. Some of their products suffer badly from dv/dt coupling from fast edges which gives false output signals. It's fairly easy to screen the transducer using an electrostatic shield made from self-adhesive copper foil with a flying lead to earth.
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If we learn from our mistakes I'm getting a great education!
RE: AC current sensing
At 600 A - that seems to be a natural choice.
Are high frequencies involved? "Automation controller" - sounds like 50 or 60 Hz to me.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: AC current sensing
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If we learn from our mistakes I'm getting a great education!
RE: AC current sensing
RE: AC current sensing
RE: AC current sensing
I think they are Hall Effect 20 kHz seems to be mid range for the transducer. Why do you need so high?
Roy
RE: AC current sensing
What does "load gets to 600 amps on any phase I need to dump the load very quickly" mean in quantifiable terms? If that 600A is rms, then you need at least a full cycle to know the rms magnitude. If you need something faster than that, you will have to use a level detector set at 848A, but then you will be subject to tripping on transient currents, such as inrush.
RE: AC current sensing
Checonbill, you may find what you need at this website try this URL.
http://www.loadcontrols.com/products/products.html
Tom
None of us is as smart as all of us.
RE: AC current sensing
Would You please explain the following: we have a conventional current transformer (CT) and we have a Rogowski Coil Current Sensor (RCCS). Both use the same principle - Faradey's Law, right?
Then why do we have such a narrow frequency range for CT - just 50/60 Hz, while RCCS has a very broad one? For example AFAIK a sensor from Phoenix Contact has a (30...6000)Hz range with 4-20mA output - very good comparing to conventional CT.
Is it somehow related to the fact that CT has iron core (saturation & hysteresis) while RCCS has a non-magnetic core?
RE: AC current sensing
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: AC current sensing
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: AC current sensing
RE: AC current sensing
And what can You say about CT?
RE: AC current sensing
A Rogowski coil bandwidth is essentially limited by the integrating amplifier and the interconnecting cable rather than the coil. BW's into the MHz are achieveable with enough care to the design.
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If we learn from our mistakes I'm getting a great education!
RE: AC current sensing
That has made a lot of sense to me. I thought through this idea and I had a question to it: does the degree of saturation depends on the secondary circuit ohmic resistance? I mean I came to a conclusion that:
1. If there is an ideal case when total ohmic resistance of the secondary circuit equals to zero (i.e. R2 = 0 [ohm]) then there is no saturation at rated current below nominal frequency. The magnitude of the flux in the core will be the same at 20Hz as at 50Hz (let's forget about 0Hz).
2. If there is a real case when total ohmic resistance of the secondary circuit is non-zero then we have a situation where the greater the R2 is the more the degree of saturation which we will face at lower frequencies at rated current. In other words the greater R2 is the more the magnitude of the core flux at lower frequences. And, BTW, this sounds good at any frequency - I mean that it is true for 50Hz: the more I burden my CT the more it saturates! And at lower frequences we just have a situation where the same ohmic resistance becomes, so to say, "heavier" for CT to carry than is was at 50Hz.
ScottyUK, did I get Your idea correctly?
RE: AC current sensing
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If we learn from our mistakes I'm getting a great education!
RE: AC current sensing
Please find attached link on the issue.
Guys sorry, Russian lang.
http:
Best Regards.
Slava
RE: AC current sensing
Skogsgurra, You mentioned that Rogowski Coil has no leakage reactance.
I looked through the operating principle of this device again and I came to conclusions that:
1. Actually there is leakage reactance in the secondary of the Rogowski Coil but since secondary current is negligible (almost zero) so the influence of this reactance is naught.
2. Rogowski Coil is smth very similar to conventional current transformer if leave CT secondary open and change an iron core to a non-magnetic one. And add electronic integrator.
What do You think about it?
RE: AC current sensing
VladM is me - I am on www.electrik.org also
Best Regards.
Volodya
RE: AC current sensing
Yes, of course, there is a small leakage reactance also in a Rogowski coil. But not significant for the result. As you know, every conductor has some inductance, so you can hardly avoid it.
The standard CT works with ampereturn balance. The Rogowski does not. So, I do not hink they should be compared the way you do. But, you are right in the observation that removal of iron from a CT makes it similar to a Rogowski coil. The same way as a transformer turns into a near short if you remove the core - if you get my drift. Correct observation, but can confuse those not in the know and attract lots of unecessary comments. We have had enough of that in other threads.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: AC current sensing
RE: AC current sensing
I have just had a qick look at the link to electrik.org and I didn't even know where to start with the Cyrillic alphabet. I'm am now even more impressed at your language skills than I was previously.
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If we learn from our mistakes I'm getting a great education!