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adiabatic equation - 2.5 2c SWA

Stewart Mason
I don't get involved with adiabatic equations all to often, hence I'm a bit rusty! I'm trying to calculate the R1+R2 for a 2 core 2.5mm SWA. Obviously the R1 is the easy bit, I'm struggling with the SWA as the R2.  I saw a link to a table on the old forum but I can't find it now. Any ideas?


Thanks Stewart
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    Graham, now you are confusing me.


    I can see the point of manufacturing gear to cope with 6, 10, 16 kVA on the basis that the installation may be literally next door to the transformer (so far I have resisted the temptation to knock on the door of our neighbour across the road with my MFT at the ready) but I am not sure why you mention the maximum (PME) external loop impedance.


    The adiabatic tells me that 4 sqmm CPCs will suffice for all circuits given a Ze of 0.2 Ω - I cannot be more than 1150 A. If Ze is anywhere up to 0.35 Ω, the equation holds good.


    However, I have assumed that Ze is 0.35 Ω when it comes to the ends of circuits because I need to be satisfied that Zs will be low enough to satisfy the requirements of ADS. If Ze is lower, the conditions are still met.


    If I have that wrong, please let me know whilst I still have time to change the design.
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  • 0
    Graham, now you are confusing me.


    I can see the point of manufacturing gear to cope with 6, 10, 16 kVA on the basis that the installation may be literally next door to the transformer (so far I have resisted the temptation to knock on the door of our neighbour across the road with my MFT at the ready) but I am not sure why you mention the maximum (PME) external loop impedance.


    The adiabatic tells me that 4 sqmm CPCs will suffice for all circuits given a Ze of 0.2 Ω - I cannot be more than 1150 A. If Ze is anywhere up to 0.35 Ω, the equation holds good.


    However, I have assumed that Ze is 0.35 Ω when it comes to the ends of circuits because I need to be satisfied that Zs will be low enough to satisfy the requirements of ADS. If Ze is lower, the conditions are still met.


    If I have that wrong, please let me know whilst I still have time to change the design.
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