Measurement of current sensing transformer (CT)secondary winding

[albertywk]

Dear all

I measure a current sensing transformer (CT) secondary coil winding getting about 700 ohm by ohmmeter and about 7H in inductance by LCR meter,do you think it is normal?

Thanks!

 

[Harald Kapp]

Judging these parameters depends on the application, mainly the primary current range and also the size of the transformer's core. The impedance seems to be quite on the high side (I'd expect less than 100Ω). This can lead to a large phase shift due to the resulting time constant (L/R). Unless you have a known good reference or a datasheet it is not possible to answer your question with "good" or "bad".

 

[albertywk]

This current sense transformer is as attached pic

 

[albertywk]

For the current sensing transformer (CT)..
I already compared the measurement of the secondary winding with good one ,the result is 750 ohm for both CT by ohmmeter but about 8H for suspected fault CT & 11H for good CT in inductance by LCR meter,
do you think the suspected fault CT is faulty?
Why even their ohm value is same but different in inductance value?
Pls kindly advice.

 

[duke37]

Shorted turns will have little effect on the resistance if the turns are close together. Even shorts between one widing layer and the next may be hard to detect.

The shorted turns will have a large effect on the inductance due to the eddy currents which are generated. I would guess that you have a faulty transformer, possibly caused by over voltage. Did you have a load on the secondary?