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Line impedance query

me1899
Hi 


I am looking at a job where a supply to a replacement CT scanner has to be calculated.


The current scanner is fed by a cable with line impedance 0.06 at source end of the sub panel that feeds it.


The new scanner must have a line impedance no more than 0.06 so basically I can't use the way on the current panel.


The client engineer has said to run from the intake and provide a cable calc to prove the line impedance is OK for the new scanner feed (this is D and B).


I am using AMTECH and was wondering if there was a way to output line impedance or if I need to show a calculation another way?


The client engaged a firm to do line impedance tests, and their report shows values measured between L1-L2, L2-L3 and L1-L3, but looks like they did testing at the sub panel and not at the intake.


This is basically like PSCC right? So I can get PSCC from AMTECH, divide by root 3 and work out impedance from there?


Am I on the right track? Assistance would be much appreciated.


Regards


Anisur
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  • 0
    Thanks OMS, that is useful to the OPer, I had not talked about the load characteristic, which is to take many short exposure Xrays as the scanner and tube rotate, going from zero to perhaps 70 kVA many times a second! Normal rotations are up to 2 revolutions per second depending on manufacturer and design, and 100 or more exposures per rev, so this is a fairly horrible load. It may be that the load is smoothed somewhat by electronic power supplies and large capacitors, but because the tube voltage is somewhere around 100kV the switching is not EHT but in the final voltage inverter. I would be most worried if this large fat cable was not all the way to the TX supply primary switchboard, as voltage fluctuations etc. would not be good for anything else. Anyway, more help from the manufacturer would be a good idea.


    Kind regards

    David
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  • 0
    Thanks OMS, that is useful to the OPer, I had not talked about the load characteristic, which is to take many short exposure Xrays as the scanner and tube rotate, going from zero to perhaps 70 kVA many times a second! Normal rotations are up to 2 revolutions per second depending on manufacturer and design, and 100 or more exposures per rev, so this is a fairly horrible load. It may be that the load is smoothed somewhat by electronic power supplies and large capacitors, but because the tube voltage is somewhere around 100kV the switching is not EHT but in the final voltage inverter. I would be most worried if this large fat cable was not all the way to the TX supply primary switchboard, as voltage fluctuations etc. would not be good for anything else. Anyway, more help from the manufacturer would be a good idea.


    Kind regards

    David
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