CT Saturation article confusion

[WiringBoy]

Hi

I have gone through the article below and I am not sure if I have it wrong or article has the other way round.

http://www.idc-online.com/technical..._engineering/current_transformer_concepts.pdf

On Page 2 of pdf, It says in low excitation, Im > Ib and other two cases of medium and high excitation Ib keeps increasing as excitation increases. It defined Ib as burden current and Im is magnetizing current.
It also defines case#3, high excitation as open switch which excitation is very high.

Here is what I know about CT saturation, when CT gets saturated, the magnetization reactance component acts like a short and the currents gets shunted to it and no current get reflected in the burden. but the articles is saying the opposite on page 2.

then on page Page, 4 it is saying what I am saying. which means during overfluxing/over-excitation, no change of flux that means the virtual switch as shown on page 2 closes shunting all the ratio current away from the burden until a
reversal of current and integration becomes negative to reduce the flux What am I missing.


I would appreciate your input.

 

[alehman]

The article says for Case #3, high excitation, the switch is closed during saturation and open during flux change.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[WiringBoy]

Thanks for your input. Fig.1, pic#3, shows switch open during saturation, which is not correct, it should be shorted out during high excitation.

am I missing something in your response ?

 

[TSun]

The figure seems to be showing the circuit model for a high excitation level, but still below saturation. Basically operating at the high end of its design. Think of a CT with standard burden operating at its nominal current.

 

[alehman]

WiringBoy,
I think that's intended to be a generic switch symbol, not necessarily indicating position as open or closed. The text describes under what circumstances the switch is open and closed.


Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.