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inductance calculation

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franticEB

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Hi, i want to calculate the value of the inductance of secondary of current transformer...
This transformer is made with a 2*sg89/29 C core with a gap of 1.35mm

(**broken link removed**)

Catturacores.PNG

I'm not able to find the value of relative permeability and the Al value of the core in order to calculate the inductance...

I have only the number of turns...

Could you help me?
Thanks
 

Current transformer with air gap? Very unusual. What do you want to achieve with it?
 

It is a sensor for leakage currents in track circuits... my purpose is only to obtain its electrical charateristics to make a spice model
 

I have never seen a CT with an air gap, its completely the wrong approach.

Inductance with an air gap can be calculated, but its never very accurate, mainly because of fringing around the gap, and other geometry related effects.

But if the gap is fairly large, >1% of the path total length, you can make a guesstimate, by blindly assuming all of the reluctance is contained within the gap.

Inductance in mH = 4 Pi x 10 ^-7 x turns squared x gap area in mm squared divided by the gap width in mm.

The 4 Pi times ten to the minus seven is the reluctance of air.

Reference: "Switchmode power supply handbook" by Keith Billings page 2.28
 
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But if the gap is fairly large, >1% of the path total length, you can make a guesstimate, by blindly assuming all of the reluctance is contained within the gap.
Click to expand...

That's surely substantiated in this case because silicon steel µr is several thousands.

The "sensor for leakage currents in track circuits" may be used as di/dt sensor with open circuit secondary rather than current transformer. Or is it equipped with a hall sensor in air gap?
 

I used to work for Westinghouse Signals R&D, and I am pretty familiar with various types of "track circuits".

Not at all sure exactly what it is you are trying to measure here ?
 

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