Detecting saturation of current transformer. 1

[honeykuwait]

Dear all,
You may find this silly, but I am serious to know is there any method to detect the condition of current transformer getting saturated?

 

[Skogsgurra]

Yes, if you know that your primary current is a sine with low distorsion, then you can see saturation as an increase in third and other odd harmonics in the secondary current.
Even if you have distorted current, you can see that THD increases when current goes beyond the saturation limit.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[honeykuwait]

skogsgurra,
Request advise a method or instrument for measuring the odd harmonics.

 

[Skogsgurra]

One of the simplest methods is to buy a USB A/D which turns your laptop into a digital scope. They cost around USD 100 in their simplest form and they come with FFT software that makes harmonics measurement easy. There are more advanced ones, like the PicoScope models, that can cost up to USD 1000 - some models are a little more expensive. With them you get very good resolution and deep memory. Can be used for lots of other purposes as well.

Then, a digital scope can also be used. They can easily be a lot more expensive. From a few hundred dollars up to 10 - 30 kUSD. There is a lot to choose from.

Google "USB scope" and variations thereof.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Hi Gunnar;
Can you make any recomendations as to which software to look for, or does Fast Fourier Transform say it all?
In the mean time I will Google USB scope as suggested.
Thanks
Bill

 

[Skogsgurra]

Yes, FFT (Fast Fourier Transform) says it all. For these measurements, you do not need much band-width or resolution. An eight bit A/D is sufficient. Although I usually use twelve bits to have a lower noise floor and more dynamic range.

The USB data collection devices come bundled with (or downloadable) quite good software. At least good for these purposes.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...