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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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  • Former Community Member
    0 Former Community Member
    It's actually more about the power than the voltage per se. Typical rotating anodes in medical x ray sets draw in a huge amount of power very quickly and in a CT scan that is often very repetitive of the scan.


    To get an x ray you need an arc in a vacuum (so be careful about standing about in front of operational HV vacuum circuit breakers) - if the power delivery  and the voltage are unstable, you don't get the x ray you expect to get (ie poor image quality is down to an inability to supply the power and an inability to maintain the voltage (typically around 75kV).


    Just follow the instructions of the set manufacturer - he knows more about how his set operates in terms of stored energy and what parameters it's been  designed to. The market is hugely competitive in terms of the number of slices so it is very much a war in terms of the image quality output between manufacturers of medical x ray sets.


    No one would be measuring this with a cheap electrical meter - it's usually by calculation and verification at commissioning. I've seen a number of commissioning visits aborted because of supply line impedance issue. They can be solved by adding capacitance but that's fearsomely expensive to do when not required.


    regards


    OMS
Reply
  • Former Community Member
    0 Former Community Member
    It's actually more about the power than the voltage per se. Typical rotating anodes in medical x ray sets draw in a huge amount of power very quickly and in a CT scan that is often very repetitive of the scan.


    To get an x ray you need an arc in a vacuum (so be careful about standing about in front of operational HV vacuum circuit breakers) - if the power delivery  and the voltage are unstable, you don't get the x ray you expect to get (ie poor image quality is down to an inability to supply the power and an inability to maintain the voltage (typically around 75kV).


    Just follow the instructions of the set manufacturer - he knows more about how his set operates in terms of stored energy and what parameters it's been  designed to. The market is hugely competitive in terms of the number of slices so it is very much a war in terms of the image quality output between manufacturers of medical x ray sets.


    No one would be measuring this with a cheap electrical meter - it's usually by calculation and verification at commissioning. I've seen a number of commissioning visits aborted because of supply line impedance issue. They can be solved by adding capacitance but that's fearsomely expensive to do when not required.


    regards


    OMS
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