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Eddy currents in SWA

Stephen Biddle

We have a very high current industrial heater (about 1,000A) we are using SWA, but due to the large diameter we are using single core to make the bending easier. It seems to me that we will get eddy currents in the armour since it forms a shorted turn. Does anyone have any experience of this? In a ferrous enclosure the eddy currents are prevented with a slot and in a transformer any screens around the windings are have an insulation to prevent this.



 



Is the effect perhaps negligible ie wrt to the cable resistance?



 



Someone here had a theory that it would be better if we earthed the screen only at one end but I can't see how that would make any difference personally.


Help please


Stephen


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  • 0
    Stephen,

    Normal practice to minimise eddy currents is to install the three single core phase cables in a trefoil arrangement and then every so often switch the phase rotation.

    Thus start   L1           then switch to  L1

                    L2  L3                             L3  L2

    and keep switching at regular intervals.

    As an aside, have you not thought of using several three core cables in parallel - this should prevent the problem.
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  • 0
    Stephen,

    Normal practice to minimise eddy currents is to install the three single core phase cables in a trefoil arrangement and then every so often switch the phase rotation.

    Thus start   L1           then switch to  L1

                    L2  L3                             L3  L2

    and keep switching at regular intervals.

    As an aside, have you not thought of using several three core cables in parallel - this should prevent the problem.
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