Hi, anyone knows if exist a specific formula to calcolate self and mutual inductance of a 3-polar cable with a fourth conductor used as shield (for example a 3x95mm2+50c cable)? Thanks.

 

What length of cable is in question?

The procedure described here should provide a means of determining the voltage drop across the inherent series inductance equivalent in one of the wire strands.:

Place a carbon resistor ... essentially no significant inductance ... in series with one of the cable wire strands. Apply an AC voltage across the two terminal ends of this assembly ... One at the resistor and the other at the extreme end of the cable wire strand. Measure the voltage drop across the resistor and calculate the current through the resistor and wire strand. Use the wire cross sectional area, length, and resistivity to calculate a resistance value for the wire strand. Using this resistance and the previous current calculation, find the voltage drop across the wire resistance. Add the resistor voltage drop to the wire resistance voltage drop. Subtract the sum from the voltage that is applied to the entire unit ... resistor plus wire.
The resulting difference will be the voltage that exists across the inductance existing in the test strand ...
correction ... subtraction of the sum resistance voltage is incorrect ... must use Pythagorean Theorem.

 

What length of cable is in question?

The procedure described here should provide a means of determining the voltage drop across the inherent series inductance equivalent in one of the wire strands.:

Place a carbon resistor ... essentially no significant inductance ... in series with one of the cable wire strands. Apply an AC voltage across the two terminal ends of this assembly ... One at the resistor and the other at the extreme end of the cable wire strand. Measure the voltage drop across the resistor and calculate the current through the resistor and wire strand. Use the wire cross sectional area, length, and resistivity to calculate a resistance value for the wire strand. Using this resistance and the previous current calculation, find the voltage drop across the wire resistance. Add the resistor voltage drop to the wire resistance voltage drop. Subtract the sum from the voltage that is applied to the entire unit ... resistor plus wire.
The resulting difference will be the voltage that exists across the inductance existing in the test strand ...
correction ... subtraction of the sum resistance voltage is incorrect ... must use Pythagorean Theorem.

The cable length is 100 meter. Buy i donn't

 

What length of cable is in question?

The procedure described here should provide a means of determining the voltage drop across the inherent series inductance equivalent in one of the wire strands.:


Place a carbon resistor ... essentially no significant inductance ... in series with one of the cable wire strands. Apply an AC voltage across the two terminal ends of this assembly ... One at the resistor and the other at the extreme end of the cable wire strand. Measure the voltage drop across the resistor and calculate the current through the resistor and wire strand. Use the wire cross sectional area, length, and resistivity to calculate a resistance value for the wire strand. Using this resistance and the previous current calculation, find the voltage drop across the wire resistance. Add the resistor voltage drop to the wire resistance voltage drop. Subtract the sum from the voltage that is applied to the entire unit ... resistor plus wire.
The resulting difference will be the voltage that exists across the inductance existing in the test strand ...
correction ... subtraction of the sum resistance voltage is incorrect ... must use Pythagorean Theorem.

But i don't have the possibility to measure it physically, i have to do an estimation of It. So this Is why i asked if there Is some theoretical expression based on cable geometry.

 

The self inductance should be constant.....but the reactance will depend on the physical layout.

You could resonate a straight meter of cable with a cap. for self inductance. Or email manufacture.

You could ground the far end of a 100 ft installed cable......ground near end thru cap......couple and resonate with dip meter or signal gen.

Or, I googled "self inductance of wire".....first hit was this.

https://www.eeweb.com/tools/wire-inductance

 

Take a look at the following link:
https://quickfield.com
...
There should be a way to construct an approximate model of your geometry.
The only other option is commercial physics modeling software.